Content uploaded by Balunkeswar Nayak
Author content
All content in this area was uploaded by Balunkeswar Nayak on Aug 21, 2018
Content may be subject to copyright.
This article appeared in a journal published by Elsevier. The attached
copy is furnished to the author for internal non-commercial research
and education use, including for instruction at the authors institution
and sharing with colleagues.
Other uses, including reproduction and distribution, or selling or
licensing copies, or posting to personal, institutional or third party
websites are prohibited.
In most cases authors are permitted to post their version of the
article (e.g. in Word or Tex form) to their personal website or
institutional repository. Authors requiring further information
regarding Elsevier’s archiving and manuscript policies are
encouraged to visit:
http://www.elsevier.com/authorsrights
Author's personal copy
Review
Impact of food processing on the glycemic index (GI) of potato products
Balunkeswar Nayak
a,
⁎,JoseDeJ.Berrios
b
, Juming Tang
c
a
School of Food and Agriculture, University of Maine, Orono, ME 04469, USA
b
Processed Foods Research Unit, USDA-ARS-WRRC, Albany, CA 94710, USA
c
Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164, USA
abstractarticle info
Article history:
Received 6 June 2013
Accepted 11 December 2013
Keywords:
Glycemic index
Glycemic load
Potato
Baking
Boiling
Microwave cooking
Roasting
Extrusion
Potatoes are one of the most popular carbohydrate foods in industrialized and some developing countries. However,
contradicting arguments and misconceptions on potatoes as a high glycemic index (GI) food is directly affecting po-
tato consumption during the past years. Potato varieties, maturity level, starch structure, food processing techniques
and composition of the meal contribute to the GI of potatoes. Domestic boiling, baking, microwave cooking, oven
cooking, extrusion and frying result in different degrees of gelatinization, and the crystallinity of starch in potato.
French fried potatoes contain more resistant starch whereas boiled and mashed potatoes contribute to significant
digestible starch. Extrusion processing conditions could affect the starch physicochemical structure and resulting
nutritional value. Extrusion cooking makes more gelatinized starch than conventional cooking methods. Cooling
or storing after processing of potatoes significantly reduces the GI due to retrogradation of starch molecules. This
review provides a brief idea about the glycemic index, glycemic load, and their importance to human diseases,
and detail information on the effect of food cooking methods on the glycemic index of potatoes.
© 2013 Elsevier Ltd. All rights reserved.
Contents
1. Introduction............................................................... 36
2. Glycemicindexandhumanhealthissues.................................................. 36
2.1. Glycemicindexdetermination ................................................... 36
2.2. Invitromethods ......................................................... 36
2.3. Humanhealthissues........................................................ 37
3. GeneralstrategyforproducinglowGIpotatofoodproducts ......................................... 38
3.1. Potatocultivarandmaturity .................................................... 38
3.2. Starchstructure.......................................................... 39
3.3. Dietary fibercontent........................................................ 39
3.4. Lipid............................................................... 40
3.5. Processingcondition........................................................ 40
3.6. Annealingandhydrothermalconditions............................................... 40
3.7. Foodmatrixandadditives ..................................................... 41
4. FoodpropertiesrelatedtoGIasaffectedbyprocessing............................................ 41
4.1. Processing/cooking ........................................................ 41
4.2. ExtrusionprocessconditionsandGIofpotatoproducts........................................ 42
4.2.1. Gelatinizationofstarchgranules .............................................. 42
4.2.2. Molecularweightdegradation............................................... 42
4.2.3. Retrogradation...................................................... 43
4.2.4. Amylose–lipidcomplex.................................................. 43
4.3. EffectofcoolingandstorageonGI ................................................. 43
5. Summary................................................................ 44
References .................................................................. 44
Food Research International 56 (2014) 35–46
⁎Corresponding author. Tel.: +1 207 581 1687.
E-mail address: Balunkeswar.nayak@maine.edu (B. Nayak).
0963-9969/$ –see front matter © 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.foodres.2013.12.020
Contents lists available at ScienceDirect
Food Research International
journal homepage: www.elsevier.com/locate/foodres
Author's personal copy
1. Introduction
Potatoes are one of the most popular vegetables used as food in the
USA. Per capita consumption of potato in the US was approximately
110.3 lb/person/year. Nearly 80% of consumers eat potatoes in some
or other way 3.6 times in every two weeks (National Potato Council,
USA, 2013).
According to National Potato Council of United States (2013) proc-
essed potatoes account for major consumption since 2011 in the USA
(Table 1). Among all potatoes, 26% were consumed as fresh or without
processing, whereas the remaining 74% were utilized in some or other
forms of processing. Frozen potatoes (40%) were the most consumed
processed potato product in the processed category in the USA. Howev-
er, a declinein potato consumption is observed in recent years in all age
groups (USDA, Economic Research Service, 2013). Foods with high GI
values are considered potential contributors to mainly the type 2 diabe-
tes (American Diabetes Association, 2002). This conclusion could be
misleading as the perception was based on the studies published before
the GI of potatoes was well studied.
Potatoes and potato-products yield variable glycemic responses. For
example, the published GI values of potato range from very low (23 for
an unspecified cultivar) to very high (144 for boiled Desiree) (Foster-
Powell, Holt, & Brand-Miller, 2002; Soh & Brand-Miller, 1999). The
variation in the GI values of potato-products may be due to a number
of factors such as potato cultivar, maturity, starch structure, processing,
and storage conditions. Lynch et al. (2007) reviewed the glycemic index
of potato focusing some of the above factors and their importance to in-
dustry. Among all other factors, processing plays a major role influenc-
ing the final GI values of potato products (Fig. 1). The importance of
physical activity and its relation to improving human health and
reducingrisk of chronic diseases by preventing obesity and insulin resis-
tance has been reported (Solomon & Thyfault, 2013; Welty, 2013). This
paper aims to provide a general overview of basic information about GI,
glycemic load (GL), and the effect of processing on the GI values of po-
tato and potato-products.
2. Glycemic index and human health issues
2.1. Glycemic index determination
Current dietary guidelines recommend that carbohydrates in human
diet comprise 45–65% of total calories; and dietary carbohydrate intake
come primarily from complex carbohydrates or starches (Institute of
Medicine, 2005). The nutritional properties of carbohydrate in foods
may be described on the basis of physiological effects: availability for di-
gestion and/or absorption in the gastrointestinal tract, i.e. ability to raise
blood glucose. Such classification of the blood glucose raising potential
of carbohydrates is referred to as the GI of the food. The GI was intro-
duced by Jenkins and co-workers in the early 1980s, and is a quantitive
concept of ranking carbohydrate foods based on the effects of postpran-
dial glycaemia (Jenkins et al., 1981). Venn and Green (2007) reviewed
on the issues related to measurement of GI, GL and their effect on
diet-disease relationships.
The GI is defined as the incremental blood glucose area following the
test food, expressed as a percentage of the response to an equivalent
carbohydrate portion of a reference food taken by the same subject
(Wolever, Jenkins, Jenkins, & Josse, 1991)asshowninFig. 2.The
World Health Organization (WHO) provides GI methodology guidelines
for classifying food according to GI ratings (Table 2) with the protocol
stating “to determine the GI of the food, the tests illustrated in Table 3
would be repeated in six more subjects and the resulting GI values aver-
aged. Normally, the GI for more than one food would be determined in
one series of tests, for example, each subject might test four foods once
each and the standard food three times for a total of seven tests in ran-
dom order on separate days.Subjects are studied on separate days in the
morning after a 10–12 h overnight fast. A standard drink of water, tea or
coffee should be given with each test meal”. The area under curve (AUC)
is calculated according to thetrapezoidal rule in geometry. The standard
or reference food usually taken is glucose or white bread. The GI rating
in percentage is calculated as follows:
GI rating %ðÞ¼ Area under curve AUCðÞfor the test food
Area under curve AUCðÞfor the reference food 100
Based on the above methodology, GI values of test foods using white
bread are approximately 1.4 times than those calculated based on glu-
cose as reference food. The differences in GI could be attributed to the
differences in the rate of absorption of the carbohydrates i.e. the slower
the rate of carbohydrate absorption, the lower the increase of blood glu-
cose and hence, lower the GI value. For example, carbohydrate foods
consumed in isoglucidic amounts producedifferent glycemic responses
(Jenkins et al., 1981).
The postprandial blood glucose response is influenced not only by
the GI of the food, but also by the amount of ingested carbohydrate.
Therefore, glycemic load (GL) is another parameter to understand the
impact of blood sugar upon the carbohydrates and calculated as the GI
of the test food multiplied by grams of carbohydrate per serving size.
Glycemic index is based on a specific quantity and carbohydrate content
of a test food. GL is calculated by multiplying the weighted mean of the
dietary GI by the percentage total energy from the test food or grams of
carbohydrate per serving. In other words, each unit of dietary GL repre-
sents the equivalent glycemic effect of 1 g carbohydrate from a refer-
ence food such as white bread (Willett, Manson, & Liu, 2002). A
hypothesis on the potential mechanism linking glycemic load with the
development of type 2 diabetes is illustrated in Fig. 3.Investigatingon
the long-term effect of varying the source or amount of dietary carbohy-
drate on postprandial plasma glucose, insulin, triacylglycerol, and free
fatty acid concentrations in subjects with impaired glucose tolerance,
however, Wolever and Mehling (2003) reported that reducing the gly-
cemic index or amount of carbohydrate intake in food has no change on
postprandial plasma glucose. The same investigators also reported that
the observations based on GI and GL separately have a differenteffect on
postprandial insulin, triacylglycerols and free fatty acids.
2.2. In vitro methods
In vitro studies are designed to simulate digestion in the small intes-
tine and measure the rate of starch digestion as an alternative to in vivo
testing of the glycemic response to carbohydrate foods. Basically, three
classifications of starch most starchy foods contain i.e. (i) rapidly digest-
ible starch (RDS), (ii) slowly digestible starch (SDS), and (iii) resistant
starch (RS) was introduced for nutritional purposes (Englyst, Liu, &
Englyst, 2007). RDS consists mainly of amorphous and dispersed starch,
found in high amounts in starchy foods cooked by moist heat. SDS is ex-
pected to be completely digested in the small intestine, but for one rea-
son or another, it is digested more slowly. RS is indigestible by body
enzymes. In an in vitro method, the physico-chemical properties of a
carbohydrate food are described by measuring the rate and extent of
glucose release by enzymatic digestion under controlled conditions
(Englyst, Englyst, Hudson, Cole, & Cummings, 1999). Additional tests
in an in vitro method might include chewing of test foods by subjects
Table 1
Share of potato utilization in 2011 in USA (National Potato Council, 2013).
Forms of utilization % Potato
crop
i. Fresh potatoes (table potatoes) 26.0
ii. Frozen potatoes (frozen fries, tater tot, spiral fries, home fries,
wedges and frozen whole potatoes)
40.0
iii. Potato chips (including canned shoestring potatoes) 15.0
iv. Dehydrated potatoes (including extruded potato chips) 11.0
36 B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
rather than mechanical homogenisation of foods (Akerberg, Liljeberg,
Granfeldt, Drews, & Bjorck, 1998; Granfeldt, Bjorck, Drews, & Tovar,
1992), the use of proteolytic enzymes in addition to amylases (Goni,
Garcia-Alonso, & Saura-Calixto, 1997) and dialysis tubing to imitate
the small intestine (Granfeldt et al., 1992). Investigating on a chemically
modified corn, Chunga, Shinb, and Limc (2008) reported that both the
in vitro digestibility and estimated glycemic index of starch could be
changed by the chemical modifications which are currently practiced
for the preparation of food starches, such as oxidation, acetylation,
hydroxypropylation, and cross-linking. While cross-linking induced
substantial changes in pasting characteristics of starch, it did not affect
starch digestibility as much as oxidation or substitutions. The substitu-
tion (hydroxypropylation and acetylation) and oxidation contribute in
raising the amount of resistant starch (RS) content by decreasing SDS
content in prime starch, and decreasing RDS content in gelatinized
starch.
Granfeldt et al. (1992) derived a hydrolysis index (HI) by calculating
the area under a hydrolysis curve from plotting the rate of glucose re-
leased over a period of 180 min using white-wheat bread as a reference.
Using the HI method of Granfeldt et al. (1992) to predict the GI of six dif-
ferent potato varieties (Asterix, Bintje, King Edward, Frieslander, Platina
and Rocket), which were boiled, Leeman, Barstroem, and Bjoerck
(2005) found that the predicted GI was high for all of the varieties irre-
spective of tuber size. In another method using the techniques of
Englyst, Kingman, and Cummings (1992),Kingman and Englyst
(1994) reported that digestion rates after processing by different
cooking methods (boiling, frying, oven and microwave baking) showed
no differences between potato varieties (Marfona, Maris Piper, Belle de
Fontenay and Desiree) and between processing methods. Another
in vitro study tested a variety of potato products, fresh potatoes, instant
mash, crisps and potato flour and all gave a high estimate for the GI
value (Garcia-Alonso & Goni, 2000).
Recently, an artificial neural network has been designed to predict
the GI of unknown food samples. The method used foods with known
GI values and tested them using an in vitro method simulating human
digestion under both stomach and small intestine conditions. The
digestate was analyzed for glucose, fructose, sucrose, lactose, galactose,
and maltitol using HPLC. These results were combined with nutritional
information (protein, fat and total dietary fiber content) of the test food,
and reported or tested in vivo GI values were used as the calibration set
of data. The sample set consisted of 72 food types and a correlation of
r
2
= 0.93 was obtained, indicating a good predictive ability of the
method (Magaletta et al., 2010).
Although the in vitro method has been proposed as an alternative
method for classifying carbohydrates and correlated with some studies
for in vivo GItesting, there are only a few foods thathave been subjected
to both testing methods for comparison (Araya, Contreras, Alvina, Vera,
& Pak, 2002; Englyst et al., 1999; Granfeldt et al., 1992). However, it is
noteworthy to mention that all potatoes tested had a high HI, and con-
sequently the predicted GI values were high, regardless of variety, prep-
aration and cold storage time in the above studies. Although in vitro
studies may not be a replacement for in vivo studies, they offer consid-
erable benefits in the speed of testing, the potential to use controlled
conditions and the freedom to test novel foods and ingredients. The
complementary application of these two approaches should provide a
clearer understanding of potato digestibility and GI.
2.3. Human health issues
Several health benefits existfor reducing the rate of carbohydrate di-
gestion and absorption by means of a low GI diet. These include: im-
proved blood glucose control (Amano et al., 2007; Brand, Nicholson,
Thorburn, & Truswell, 1985; Gilbertson et al., 2001), reduced insulin de-
mand (Frost, Keogh, Smith, Leeds, & Dornhorst, 1998), reduced blood
lipid levels in healthy adults (Ma et al., 2006) and patients with diabetes
and hypertriglyceridaemia (Jenkins, Wolever, Kalmusky et al., 1987),
improved satiety (Raben, Kiens, & Richter, 1994)andincreasedcolonic
fermentation (Jenkins, Wolever, & Collier, 1987; Regina et al., 2006). All
factors may play important roles in the prevention of several chronic
diseases, such as obesity, type-2 diabetes, coronary heart disease and
several forms of cancer.
The health benefits of a low GI diet are supported by a number of
semi-long-term and long-term studies which suggest that diets charac-
terized by low-Gl starchy foods improve factors related to glucose and
lipid metabolism in humans (Brand-Miller, 1994). In diabetics, low-GI
diet can improve glucose tolerance (Brand et al., 1985; Brand-Miller,
1994). In hyperlipidemic patients, low GI diets can substantially lower
the levels of total serum cholesterol and, in particular, of serum
triacylglyceride. However, the mechanisms are still unclear. A possible
biological mechanism could involve the regulation of insulin sensitivity
and glucose levels by low-GI diets. In general, rapidly absorbed carbohy-
drates trigger a large insulin rise and strongly inhibit glucagon release,
followed by a rapid blood glucose fall, often less than fasting levels.
This could result in a counter-regulatory response with the release of
free fatty acids, creating an insulin-resistant environment and reducing
glucose tolerance (Boden et al., 1991; Piatti, Monti, Pacchioni, Pontiroli,
& Pozza, 1991). Ingestion of a slow release carbohydrate food produces
Processing Intrinsic properties Starch content
/ structure GI, GL
Processing properties
Matrix (Lipid, Protein)
Fig. 1. Mechanism of processing that effect glycemic Index (GI) and glycemic load (GL).
3
4
5
6
7
8
9
030 60 90 120 150 180
Plasma glucose (mmol/L)
Time (min)
High glucose response
Low glucose response
Fig. 2. The area under the curve (AUC) is calculated to reflect the total rise in plasma glu-
cose levelsover the time after eating thetest food. The GI rating (%) of highor low GI food
is calculated by dividing the AUCfor the test food by the AUC for thereference food (same
amount of glucose) and multiplying by 100 (Wolever et al., 1991).
37B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
an attenuated glucose response, so the resulting hormone responses
and effects are less dramatic.
Another physiological effect observed is a prolonged satiety follow-
ing the consumption of low-GI starchy foods, which may contribute to
long-term weight loss by reducing the food intake (Ludwig, 2002;
Maki, Rains, Kaden, Raneri, & Davidson, 2007). An inverse relationship
was noted between the satiety ranking and GI for six cereal products.
For example, as a result of high insulin response following a high-GI
meal, the hormone environment reduces the availability of two major
metabolic fuels (glucose and fatty acids), triggering a rapid return of
hunger (Aston, 2006). Many low-GI foods are high in fiber, which
slows gastric emptying. This will also increase and prolong the secretion
of some gut peptides suggested as potential satiety factors (Burton-
Freeman, Davis, & Schneeman, 2002; Pawlak, Ebbeling, & Ludwig,
2002).
Evidence is also emerging of a possible link between the prevention
of bowel cancer with low GI foods containing indigestible carbohy-
drates, such as resistant starch. Such low GI foods can increase the
amount of indigestible carbohydrates reaching the large bowel for
fermentation by colonic microflora. The fermentation of starch and
other indigestible carbohydrates yields short chain fatty acids such as
propionic and butyric acids, preferred source of energy for the cells
lining the colon shown to inhibit the proliferation of colonic cancer
cells in vitro, suggesting a preventive effect against colonic cancers
(Scheppach, Fabian, Ahrens, Spengler, & Kasper, 1988).
Several case control and prospective cohort studies suggested a di-
rect association between the GI of diet and incidence of breast cancer
(Augustin et al., 2001) and endometrial cancer (Augustin, Franceschi,
Jenkins, Kendall, & La Vecchia, 2002; Folsom, Demissie, & Harnack,
2003; Silvera et al., 2005). Carbohydrate intake may influence breast
cancer risk by affecting insulin resistance and plasma levels of insulin
and glucose (Michels, Mohllajee, Roset-bahmanyar, Beehler, & Moysich,
2007). The associations between GI and endometrial cancer risk are
stronger in older women, in overweight women with low physical ac-
tivity, and in hormone replacement therapy users. These women had
greater insulin response to their diet compared with lean and active
women. Insulin acts as a cancer promoting agent in vitro and animal
studies (Bjork, Nilsson, Hultcrantz, & Johansson, 1993; Tran, Medline,
&Bruce,1996). High GI diets may also increase oxidative stress which
may contribute to cancer risk (Augustin et al., 2003; Collins, Duthie, &
Ross, 1994). Low GI foods are often highin fiber and rich in antioxidants
and other micronutrients that may be protective in carcinogenesis.
3. General strategy for producing low GI potato food products
Because of the health benefit of low GI foods, increasedconsumption
is recommended by several health organizations in the management of
type 2 diabetes (European Association for the Study of Diabetes, Canadi-
an diabetes Association and Dietitian Association of Australia) and as
part of the healthy diet for the general population (FAO/WHO report,
1998). Potatoes are one of the major food items in developed countries,
so producing potato-products with low GI would help to reduce the
overall GI of the diet in these counties. The developmentof low GI pota-
to products is a challenge for the potato and food industries.
3.1. Potato cultivar and maturity
Starch is the most abundant constituent in potatoes after water
content. The total starch content will determine the true available car-
bohydrate content in potatoes. Depending on the botanical cultivars,
the total starch in potato varies from 70 to 90% on dry basis, leading to
the variation in GIs of potato products. Monro, Mishra, Blandford,
Anderson,and Genet (2009) reported detailed differences in the rapidly
digested,slow digested and resistance starch in New Zealand potato va-
rieties when processed and refrigerated depending on their genotype
(Table 4). GI values of peeled and boiled potatoes are reported in the
range of 56 (Pontiac) to 101 (Desiree). Very low GI values (23–41) are
reported for unspecified cultivars of potatoes grown in Africa, India
and Romania (Foster-Powell et al., 2002). Some wild cultivars exhibit
smaller GI values than common commercial cultivars grown in Western
countries. For example, bush potatoes, pencil yams and cheeky yams
grown in Australian Aboriginal regions are slowly digested in vitro
and exhibit smaller plasmaglucose and insulinresponses than commer-
cial potato cultivars (Thorburn, Brand, O'Dea, et al., 1987; Thorburn,
Brand, & Truswell, 1987). It may be possible to develop new commer-
cially available low GI potato cultivars by exploring and manipulating
the genotype of commercially exotic wild potato cultivars (Soh &
Brand-Miller, 1999).
Evaluation of eight selected cultivars of potatoes commonly con-
sumed in the UK presented a strong positive correlation between GI
value and texture rating: potatoes with flourytextures (low in moisture,
low in sugarwith high starch) were in the high GI category, while pota-
toes with firm to waxy (virtually no amylose) textures (high in mois-
ture, low starch) were in the medium category (Henry, Lightowler,
Strik, & Storey, 2005). Generally, the earlier crop varieties of potato
Table 2
Examplesof comparison of glycemicindex and glycemic loadof some common foods (The American Journal of Clinical Nutrition,July 2002; International table of glycemicindex and gly-
cemic load, University of Sydney (Australia) GI index, Foster-Powell et al., 2002). Reference food: glucose.
Glycemic index
Low (≤55) Medium (56–69) High (≥70)
Glycemic load Low (≤10) Apples (6, 38) Beets (5, 84) Popcorn (8, 72)
All bran cereal (8, 42) Cantaloupe (4, 65) Watermelon (4, 72)
Carrots (3, 47) Pineapple (7, 65) Whole wheat flour bread (9, 71)
Peanuts (1, 14) Table sugar (7, 68)
Medium
(11–19)
Apple juice (11, 40) Life cereal (16, 66) Cherrios (15, 74)
Bananas (12, 52) Wild rice (18, 57) Shredded wheat (15, 75)
Orange juice (12, 50)
Sourdough wheat bread (15, 54)
High
(≥20)
Macaroni (23, 47) White rice (23, 64) Baked russet potatoes (26, 85)
Spaghetti (20, 42) Couscous (23, 65) Cornflakes (21, 81)
Table 3
Sample blood glucose responses to the ingestion of 50 g carbohydrate.
Minute
0 1530456090120IAUC
⁎
Standard #1 4.3 6.3 7.9 5.3 4.1 4.6 4.9 114
Standard #2 4.0 6.0 6.7 5.5 5.3 5.0 4.2 155
Standard #3 4.1 5.8 8.0 6.5 5.9 4.8 3.9 179
Test food 4.0 5.0 5.8 5.4 4.8 4.2 4.4 93
⁎IAUC: incremental area under curve;IAUC is calculated as the incremental area under
the blood glucose response curve.
38 B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
(second early) and the salad potatoes tend to exhibit waxy textures
while the main crop varieties tend to have floury textures.
Potato maturity will also affect the GI of potato products. Small and
less mature potatoes tendto have lower GI valuesthan large and mature
potatoes. As potatoes mature, the quantity of amylose increases slightly
but the degree of amylopectin branching increases significantly. The
lower degree of branching in the amylopectin of less mature potatoes
may be associated to greater resistance to starch gelatinization, hence
resulting in a slower rate of starch hydrolysis in the gastrointestinal
tract and to lower GI values (Soh & Brand-Miller, 1999).
3.2. Starch structure
The glycemic index of boiled or baked potatoes in Russet, some
Australian, English and Canadian varieties ranges from intermediate to
very high i.e. 59–111 (Foster-Powell et al., 2002; Jenkins et al., 1981;
Soh & Brand-Miller, 1999; Wolever et al., 1994). Although some investi-
gators argue on possible random error (Wolever and Mehling, 2003),
some suggest that the differences could be due to the differences in
their starch structures (Brand-Miller, Pang, & Bramall, 1992). Compared
to most cereal starches, potato starches in native uncooked granules are
poorly digested in the human small intestine and reach thelarge bowel
in considerable amounts. In raw state, 87% of starch in potatoes resistdi-
gestion, whereas most cereal starches are slowly but virtually
completely digested and absorbed in vivo (Holm, Lundquist, Bjoerck,
Eliasson, & Asp, 1988). The crystallinity in granules, smaller surface-
to-volume ratio of the large potato granules, and a layer of non-starch
barrier material such as polysaccharides on the surface of starch gran-
ules result in potato granules less susceptible to digestion enzymes
(Bednar et al., 2001).
Another feature of the starch molecule which may influence nutri-
tional properties of starches is the amylose: amylopectin ratio. Under
commonly used food processing conditions, linear amylose molecules
tend to retrograde and recrystallize, resulting in extensively ordered
regions resistant to enzyme digestion and absorption in the small intes-
tine. In addition, enzyme accessibility of high amylose starch is further
hindered by incomplete gelatinization and limited swelling of starch
granules during processing. Amylose concentration in potato varies lit-
tle from 24 to 32% with effects of genotype and growing conditions. The
simultaneous “antisense”inhibition of two isoformsof starch branching
enzyme resulted in a sign ificant increase of apparent amylose content to
60–89%, comparable to commercial available high amylose maize
starches (Schwall et al., 2000). The development of potato genotypes
with high amylose content opens possibilities to significantly decrease
the glycemic response of potato products.
3.3. Dietary fiber content
Lightowler and Henry (2009) investigated mashed potatoes con-
taining 1, 2 or 3% level s of high-viscosity hydroxypropylmethylcellulose,
amodified cellulose dietary fiber and observed significant reduction in
glycemic responses in all samples than the standard mashed potato.
One of the first food components observed to reduce the glycemic re-
sponse was dietary fiber (Bjoerck & Asp, 1994; Haber, Heaton,
Murphy, & Burroughs, 1977). In 2009, the Codex Alimentarius Commis-
sion adopted a definition of dietary fiber which divided dietary fiberinto
3categories:“naturally occurring in the food as consumed”;“obtained
from food raw material by physical, enzymatic or chemical means…”;
and “synthetic carbohydrate polymers”.
A portion of dietary fiber is fermented to volatile fatty acids in the
gastrointestinal tract. The addition of viscous dietary fiber to a carbohy-
drate meal may reduce the glycemic response (Braaten et al., 1991). By
forming viscous solutions, soluble fiber delays the rate of gastric empty-
ing, reduces the mixing and diffusion in the small intestinal lumen,
and thus reduces the rate of digestion and glucose absorption by the
intestine (Fig. 4).
High
glycemic load
High insulin
demand
Postprandial
glucose rise
High late
postprandial
free fatty acids
Epitopic fat
deposition
Insulin
resistance
Hyperglycemia
β-cell
failure
a. Overweight
b. Genes
c. Low physical
activity
Fig. 3. Potential mechanisms linking a high glycemic load with the development of type 2 diabetes (adapted and modified from Riccardi, Rivellese, & Giacco, 2008).
Table 4
Effect of cooking on starch fractions of New Zealand potatoes. Bulked sample of three tu-
bers analyzed in duplicate. Valuesare expressed in wetweight basis. Adaptedfrom Monro
et al. (2009).
Cultivar Freshly cooked Cooked and refrigerated
RDS SDS RS RDS SDS RS
Draga 128 0.0 5.8 80 37 16.6
Frisia 149 10.2 10.5 75 77 14.4
Nadine 90 9.9 9.3 73 24 15.7
Desiree 149 0.5 6.3 92 51 14.0
Karaka 138 2.4 7.6 73 55 19.6
Moonlight 145 2.5 7.0 105 32 16.4
Agria 138 6.8 6.7 89 53 9.6
Fronika 132 17.2 8.1 80 67 10.7
White delight 150 0.0 6.3 111 32 13.8
Mean 135 5.5 7.5 86 47 14.5
S.E.M. 4.4 4.8 0.64 2.8 4.3 2.5
Range 90–150 0–17 5.8–10.5 73–111 20–77 9.6–19.6
RDS: rapidly digested starch; SDS: slowly digested starch; RS: resistance starch.
39B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
3.4. Lipid
Lipids in potato may also affect the digestibility of starch by the for-
mation of a complex of lipid with amylose. Amylose–lipid can be formed
in the presence of both endogenous and added lipids during food pro-
cessing. Contradictory conclusions were reached by researchers on the
effect of complex formation on the digestibility of starch. Holm et al.
(1983) reported that amylose–lipid complexes were fully digested
and absorbed in the small intestine of rats, whereas Eggum, Juliano,
Perez, and Khush (1993) reported that the complexes were not digest-
ible in the small intestineof rats. A possible explanation for such contra-
dictory results was proposed by Larsenet al. (2000). There aretwo types
of amylose–lipid complexes: complex I and complex II. Complex I melts
just below 100 °C in the DSC and exhibits little crystalline structure,
whereas complex II exhibits a melting temperature well above 100 °C
and consists of more crystallites (Biliaderis & Galloway, 1989). The
more complete crystal structure of complex II possibly renders it less
susceptible to enzymatic degradation. Mercier, Charbonniere, Grebaut,
and De la Gueriviere (1980) observed that pure potato amylose and
oleic acid formed complexes highly resistant to enzymatic degradation.
3.5. Processing condition
GIs of potato starch can be significantly reduced by chemical modifi-
cation during processing. Numerous chemically modified food starches
are available as ingredients for processed foods. Chemical reactions cur-
rently allowed and used toproduce modified starches for food use in the
United States include esterification, etherification, acid modification,
cross-linking and oxidation. Chemical modification may affect the rate
and extent of starch digestion in the small intestine. For most modified
starches,the level of indigestible starch increases as the degree of mod-
ification increases.
Raw potato starch granules have a slower digestion rate as com-
pared with gelatinized starch. When potatoes are processed, potato
starch becomes digestible, and the digestibility of starch and resulting
glycemic response of potato foods can be affected by the type and
extend of processing. For example, the GI of some potatoes were not af-
fected after boiling, microwaving and baking compared with raw/fresh
ones, whereas canning of immature potatoes decreased the GI value
compared to boiled matured potato (Desiree cv)(Lynch et al., 2007).
When subjected to thermal treatments such as heating in an aqueous
environment, crystallinity within the starch granule melts, and the
starch granules swell to a high degree (Cooke & Gidley, 1992) and even-
tually bursts, especially if shear force is applied. The transition from
crystalline to a continuous amorphous or gel phase ofstarch is called ge-
latinization. Gelatinized starch is susceptible to enzymatic degradation.
Gelatinization helps in digestion and absorption in the small intestine.
The metabolic mechanism is well supported by reported increase in
blood glucose and insulin by consuming processed foods containing po-
tatoes or potato starch (Brand et al., 1985; Vaaler, Hanssen, & Aagenaes,
1984).
During cooling, some starch molecules partially reassociate to form a
network by association of the linear starch fractions, eventually leading
to the starch retrogradation. During retrogradation, starch molecules
begin to crystallize and resistant starch is formed. Retrograded amylose
in potatoes is highly resistant to amylolysis (Ring, Gee, Whittam, Orford,
& Johnson, 1988). Repeated cycles of cooling and reheating form pro-
gressively more-resistant starch, delaying digestion and absorption,
thus reducing the glycemic response. Therefore, reducing GIs of
processed potato products can be achieved by controlling the degree
of gelatinization and retrogradation through optimizing the food pro-
cessing techniques.
3.6. Annealing and hydrothermal conditions
Heating starches above their gelatinization temperature results in
the simultaneous loss of granular, lamellar, crystalline and double
helical order. Heating at sub-gelatinization temperatures preserves
granular structures, while other levels of organization are affected
(Jacobs & Delcour, 1998; Tester & Debon, 2000). Annealing (ANN) and
heat-moisture treatment (HMT) are two hydrothermal methods that
have been used to modify starch digestibility. ANN is performed on
starch granules in excess (N60% w/w) or at intermediate water content
(40% w/w) and held at a temperature above the glass transition temper-
ature (Tg) but below the onset (To) temperature of gelatinization for a
set period of time (Hoover & Vasanthan, 1994; Tester & Debon, 2000).
HMT is also a physical modification technique that involves the
treatment of starch granules at low moisture levels (b35% moisture
w/w) for a certain time period (15 min–16 h) and at temperatures
(84–120 °C) above Tg but below the gelatinization temperature. ANN
1. Macronutrient
composition
2. Fiber content
3. Viscosity
4. Volume and structure
of the food
Stomach Small
intestine
Portal
circulation
Available food
carbohydrates
Gastric
emptying Disruption
/digestion
Rate
limiting
Rate
limiting
Fig. 4. Factors influencing the rate of digestible carbohydrate availability in the gastrointestinal tract (modified from Riccardi et al., 2008).
40 B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
can modify starches by narrowing of the gelatinization temperature
range, increasing gelatinization temperatures, increasing granule stabil-
ity, crystalline perfection, decreasing granular swelling, starch chain in-
teractions within the amorphous and crystalline domains of the
granule, formation of double helices, and decreasing amylose leaching
(Hoover & Vasanthan, 1994; Jacobs & Delcour, 1998; Tester & Debon,
2000). HMT also increases gelatinization temperatures, widens the ge-
latinization temperature range, decrease granular swelling and amylose
leaching, and increase in thermal stability in all starches (Gunaratne &
Hoover, 2002; Hoover & Manuel, 1996).
Several attempts to generate RS by ANN and HMT have been report-
ed in the literatures (Brumovsky & Thompson, 2001; Haralampu, 2000;
Lehmann & Robin, 2007; Sajilata, Singhal, & Kulkarni, 2006; Vasanthan
& Bhatty, 1998). Both treatments increase gelatinization temperatures
of potato starches. Annealing narrows gelatinization ranges, while
HMT increases the temperature range over which gelatinization is ob-
served (Jacobs & Delcour, 1998; Tester & Debon, 2000). Annealing of po-
tato starch does not (Karlsson & Eliasson, 2003)oronlymoderately
(Nakazawa & Wang, 2003) increase enthalpy of gelatinization. HMT re-
duced the gelatinization endotherms and lowered total crystallinity of
potato starch (Gunaratne & Hoover, 2002; Hoover & Vasanthan,
1994). Shin, Kim, Ha, Lee, and Moon (2005) showed that the hydrother-
mal treatment (50% moisture at 55 °C for 12 h) of sweet potato starch
increased the SDS level from 15.6% to 31.0%. Chung, Liu, and Hoover
(2009) have investigated the impact of annealing (ANN) and heat-
moisturetreatment (HMT) on rapidly digestible starch (RDS), slowlydi-
gestiblestarch (SDS), resistant starch (RS), and expectedglycemic index
of corn, pea, and lentil starches in their native and gelatinized states.
ANN was performed at 70% moisture at temperatures 10 and 15 °C
below the onset (T
o
) temperature of gelatinization for 24 h, while
HMT was done at 30% moisture at 100 and 120 °C for 2 h. The same in-
vestigated and observed that amylopectin structure and interactions
formed during ANN and HMT had a significant impact on RDS, SDS, RS
and expected GI levels of starches. In the above study, ANN and HMT in-
creased RDS, RS and expected GI levels and decreased SDS levels in
granular starches. In gelatinized starches, ANN and HMT decreased
RDS and expected GI, but increased SDS and RS levels.
3.7. Food matrix and additives
Several studies suggest that different GI values are obtained from a
food when eaten alone or included in a mixed meal (Calle-Pascual,
Gomez, Leon, & Bordiu, 1988; Hollenbeck & Coulston, 1991), while
Wolever (1990) reports that in a mixed meal with bread, rice and
pasta the relative rankings of the index remained the same and ex-
plained 90% of the observed glucose and insulin response. Sugiyama,
Tang, Wakaki, and Koyama (2003) found that the ingestion of milk
with rice resulted in a significantly lower GI than when rice was eaten
alone. Schafer, Schenk, Ritzel, Ranmdori, and Leonhardt (2003) demon-
strate a significant (P b0.05) reduction in the glucose response in a
mixed meal with potato and peas compared with a potato only meal.
Both fat and protein in a meal have been shown to moderate the influ-
ence of carbohydrate on the glucose response (Gullfford, Bicknell, &
Scarpello, 1989). A study using common toppings on baked potatoes
found that the co-ingestion of fat lowered the GI of potatoes (Estima)
by 58%, changing the GI classification from high GI to low GI whereas
co-ingestion of protein only lowered the GI of potatoes by 18% with
the classification remaining as high GI (Henry et al., 2005). Glycemic
index is also affected by food consumed at prior meals. Legumes con-
sumed at a preceding meal lower the GI of carbohydrates consumed
in a subsequent meal (Wolever, Jenkins, Ocana, Rao, & Comer, 1988).
It is clear that combining foods does influence GI and that the addition
of protein and fat to a carbohydrate containing meal can appreciably re-
duce the glycemic response (Collier & O'Dea, 1983).
The presence of some additives has influenced the GI of potato prod-
ucts. For example, Leeman et al. (2005) reported that the addition of
vinegar and olive oil in the form of a vinaigrette dressing to cooked
and cooled Sava potatoes in a salad reduced the GI by 43% compared
to the boiled potatoes served hot, whereas refrigeration alone reduced
the GI by 26%. In a separate study, acetic acid (vinegar) in the test
meal reduced postprandial glycemia by reducing the rate of gastric
emptying (Liljeberg & Bjorck, 1998). Thus, aggregating the GIs of indi-
vidual components of a meal does not reliably predict the observed GI
of the meal as a whole.
4. Food properties related to GI as affected by processing
4.1. Processing/cooking
Processing conditions alter postprandial glucose responses of starch
by disrupting the cell wall and structure of the granule and gelatiniza-
tion increases the glycemic index (Fernandes, Velangi, & Wolever,
2005). Minimizing or controlling the degree of gelatinization may in-
crease the degree of crystallinity within the starch granules. Minimal
roastinginstead of extensive steaming prior to flaking will also maintain
high crystallinity in finished products. For example, the glycemic re-
sponse of roasted flaked product was similar to the glycemic response
of raw wheat flakes (Bjorck, Liljeberg, & Ostman, 2000).
Garcia-Alonso and Goni (2000) conducted a detailed study on se-
lected starch quantities of potatoes exposed to various processing con-
ditions (Table 5). Obviously, raw fresh potatoes contain the least
digestible starch (10%), whereas boiled and mashed potatoes are more
digestible with 78 and 70% of digestible starch. However, French fries
contain around seven percent of resistant starch. The resistant starch
of fried potatoes may be partly attributed to the formation of amy-
lose–lipid complexes resistant to amylolysis.
The degree of gelatinization and starch digestibility are determined
by the initial moisture content in raw foods and the amount of water
added during heat treatment. Quantitative changes in various starches
during selected processing conditions depend on the availability of
water. Baking and deep fat frying limit the water availability and thus
fried and baked potatoes exhibit lesser quantity of total starch com-
pared to the raw and boiled potatoes. Simultaneously, the amount of re-
sistant starch also decreases in frying potatoes immediately after frying
and increases thereafter during cooling with the retrogradation (Goni,
Bravo, Larrauri, & Saura-Calixto, 1997). Quantitatively, raw potatoes ex-
hibit high resistant starch that decreases with the increase in degree of
gelatinization. The presence of sufficient water for complete gelatiniza-
tion of starch during boiling improves digestibility reducing the RS.
Highest digestibility was observed in boiled and mashed potatoes
compared to other processed potatoes (Garcia-Alonso & Goni, 2000).
This was well supported by Lunetta, Di Mauro, Crimi, and Mughini
(1995) who observed a much lower incremental glycemic response
with baked potatoes than with boiled one. Three varieties of boiled
Australian potatoes had glycemic index ranging from 87 to 101 (Soh &
Brand-Miller, 1999), some baked Russet potatoes had higher glycemic
index of 111 (Foster-Powell et al., 2002), whereas glycemic index of
boiled English new potatoes and boiled or baked Canadian potatoes
had intermediate values ranging from 59 to 70 (Jenkins et al., 1981;
Wolever et al., 1994).
In contrast, Wolever et al. (1994) found no significant difference in
boiled, baked or canned potatoes and Soh and Brand-Miller (1999) as
well as Tahvonen, Hietanen, Sihvonen, and Salminen (2006) also
supported the fact and could also not significantly differentiate the GI
in boiled, baked, microwaved or mashed potatoes (Table 6). In addition,
Table 7 provides brief GI values of various processed potatoes as
reported by various investigators. The variation in the GI could be due
to botanical differences, time of measurement after cooking and consid-
eration of different reference foods. Different peeling, cubing, slicing or
mashing methods had not affected the GI value of potato in various pro-
cessing conditions (Tahvonen et al., 2006).
41B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
4.2. Extrusion process conditions and GI of potato products
Extrusion cooking has been used for the fabrication of breakfast
cereals, pasta products, snack foods, baby foods, flat breads, and pre-
cooked flours. Among all components in potato flour, starch plays a
key role during extrusion. Upon heating and shearing during the extru-
sion process, the starch granules are fragmented,the granular crystallin-
ity is decreased and partial depolymerisation occurs, which result in a
uniform viscous starch fluid which can be described as a concentrated
suspension of fractured granules embedded in a continuous and de-
formable matrix (Barron, Buléon, Colonna, & Della Valle, 2000). Extru-
sion processing conditions of temperatures, moisture addition (starch
to water ratio) and screw speed, among others, will affect the changes
in starch physical and chemical structure, and subsequently the GIs of
the final extruded products.
4.2.1. Gelatinization of starch granules
Due to the high temperatures andpressures applied during the pro-
cess, extrusion cooking makes starch granules in potato more damaged
and gelatinized, thus more digestible than conventional-cooking
methods such as boiling or baking (Brand et al., 1985). Although the de-
gree of starch gelatinization of extruded products is normally large, var-
iations in degree of gelatinization were observed when processing at
selected extrusion conditions.
Extrusion conditions that increase barrel temperature, shear and
pressure tends to enhance the degree of gelatinization. The effect of
feed moisture content on the degree of starch gelatinization is more
complicated than the previously indicated extrusion conditions. In-
creasing the moisture content in the low moisture range (b40%) or de-
creasing the moisture content in the high moisture range (N40%) led to
increase in the degree of gelatinization of sago starch (Govindasamy,
Campanella, & Oates, 1996). Extruding starch at low moisture content
may restrict the material flow inside the extruder barrel, increase the
viscosity and residence time, subsequently increasing the degree of ge-
latinization. At high moisture content, with excess water acting as a lu-
bricant, the viscosity of the starch is low, allowing for extensive internal
mixing and uniform heating, accounting for enhanced gelatinization.
A similar effect of screw speed on the degree of starch gelatinization
has been reported. Increasing extruder screw speed above 410 rpm re-
sulted in a rise in the degree of starch gelatinization (Govindasamy et al.,
1996). The possible reason for this observation tends to be related to the
swelling of the starch granule. The authors indicated that the swollen
granules were increasingly susceptible to disintegration by the high
shear developed in the extruder during processing. Raising the screw
speed above 410 rpm tendsto increase the shearrate and lower the res-
idence time of the material under process. Moreover, the shearing ac-
tion presumably predominates over residence time accounting for
starch swelling and enhanced gelatinization of the starch observed
under this condition. Parada and Aguilera (2009) investigated on in-
vitro digestibility and glycemic response of isolated potato starch in re-
lation to granular size and degree of gelatinization and observed that
the degree of gelatinization of starch strongly affects its digestibility
in vitro and influences postprandial glycemic response.
4.2.2. Molecular weight degradation
Starch molecules are also depolymerized during extrusion process-
ing. Therefore, extrusion cooking of potato starch provides an alterna-
tive to enzymatic methods for production of linear maltodextrins for
infant foods. Both amylose and amylopectin molecules are susceptible
to molecular weight degradation, with the larger and branched amylo-
pectin beingthe more susceptible.The molecular degradation of the lin-
ear (alpha 1–4 glucose polymer) amylose occurs during extrusion
mainly at a consequence of high shear effect (Sagar & Merrill, 1995).
The molecular weight degradation of starch influences many prop-
erties of starch-based products, including nutritional values, but the
mechanisms are not well understood. Among low molecular weight
carbohydrates produced from thermal degradation are highly reactive
anhydro-compounds, e.g. 1, 6-anhydrosaccharides, which may react
with starch or fragmented starch through transglycosidation reactions
to form branched glucans which are partly resistant to amylolytic en-
zymes (Theander & Westerlund, 1987). The formation of indigestible
starch fragments may contribute to the increase of dietary fiber after
the extrusion of cereal grains (Theander & Westerlund, 1987) but this
finding was not corroborated by Politz, Timpa, and Wasserman (1994).
Strong positive correlation between specific mechanical energy
(SME) and starch molecular weight degradation during extrusion was
observed (van den Einde, Akkermans, van der Goot, & Boom, 2004). In
general, decreasing the moisture content, increasing the mechanical
shearing and increasing the temperature resulted in an increase in
degradation. The decrease in intrinsic viscosity at low temperatures
and moisture contents was only dependent on the maximal shear stress.
Table 5
Different starch quantities in various process conditions. Adapted from Garcia-Alonso and Goni (2000).
Potato Total starch (%) Resistible starch Digestible starch⁎Moisture (%)
Absolute % % w.r.t TS Absolute % % w.r.t TS
Raw 79.36 69.05 86.9 10.31 13.0 81.25
Boiled 79.36 1.18 1.5 78.18 98.5 81.25
Boiled and cooled 75.18 4.63 6.2 70.55 93.8 79.43
Raw flakes 71.97 2.80 3.9 68.57 95.3 8 .59
Mashed 71.97 2.08 2.9 69.89 97.1 86.23
Oven-cooked 65.91 3.70 5.6 62.20 94.4 79.63
French fries 59.34 6.64 11.2 52.70 88.8 17.69
Crisps 65.42 3.27 5.0 65.15 99.6 2.57
Retrograded potato flour 79.36 10.38 13.1 68.98 86.9 4.32
Total starch, resistible starch and digestible starch are inexpressed on dry basis.
NB: whole potatoes, instant mash potatoes, potato crisps and retrograded potato flours were purchased separately from the supermarket.
⁎Digestible starch is the difference between total starch and resistible starch.
Table 6
Effect if variety, cooking method and maturity on the glycemic index values of potatoes
compared to reference foods as tested with 10 subjects. Adapted from Soh and Brand-
Miller (1999).
Item Glycemic index (mean ± s.e.m.)
White bread = 100 Glucose = 100
Variety
Sebago, peeled and boiled 124 ± 10 87 ± 7
Desiree, peeled and boiled 144 ± 22 101 ± 15
Pontiac, peeled and boiled 125 ± 13 88 ± 9
Cooking method
Pontiac, peeled and boiled 125 ± 13 88 ± 9
Pontiac, peeled, boiled and mashed 130 ± 13 91 ± 9
Pontiac, peeled and microwaved 112 ± 13 79 ± 9
Pontiac, peeled and baked 133 ± 15 93 ± 11
Maturity
New, unpeeled and boiled 112 ± 17 78 ± 12
New, canned and microwave heated 93 ± 13 65 ± 9
42 B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
At higher temperatures, thermo mechanical breakdown could be split
into mechanical breakdown depending on maximal shear stress and
thermal breakdown. Greater moisture content during thermo mechan-
ical treatment resulted in more thermal breakdown and decreased the
shear stresses required for mechanical breakdown. A model for the me-
chanical degradation of starch during single-screw extrusion was devel-
oped by Davidson, Paton, Diosady, and Rubin (1984).Afirst-order
relationship between the extent of degradation and the product of the
residence time and the nominal shear stress was given. Pretreatment
of starch by steeping the cereal grains to achieve 20% moisture level re-
sulted in small losses of starch through molecular degradation during
extrusion.
4.2.3. Retrogradation
An increase in resistant starch content in extruded products can also
be promoted by retrogradation. However, the literature on formation of
resistant starch during extrusion presents contrasting results (Huth
et al., 2000;Parchure and Kulkarni, 1997; Unlu & Faller, 1998). General-
ly, increasing amylose content of starch can promote the formation of
resistant starch, supported by observation of the increase in resistant
starch in extruded high-amylose barley flour, but not in low-amylose
barley flour. Unlu and Faller (1998) also reported formation of resistant
starch during extrusion of corn meal blended with high amylose maize
starch.
The shearing action of the extruder screw, which results in degrada-
tion of amyloseinto smaller molecules that were not incorporated into a
crystalline structure, resulted in less formation of resistant starch
(Gidley et al., 1995). A negative correlation between formation of resis-
tant starch and screw speed was reported by Unlu and Faller (1998).
4.2.4. Amylose–lipid complex
The formation of a complex between amylose and fatty acids in ex-
truded material was suggested by NMR, differential scanning calorime-
ter, Iodine Spectrum and X-ray diffraction (Mercier, Charbonniere,
Gallant, & Guilbot, 1979). Such interaction leads to structural reorgani-
zation of amylose chains from spiral to helix, resulting from the fatty
acids penetrating the helical cavity of the amylose and forming a
complex. The amylose–lipid complex was only detected in starch con-
taining both amylose and lipid, but not in extruded potato starch free
of lipid or waxy starch free of amylose (Mercier et al., 1979). This forma-
tion results in thermally stable and water-insoluble starch, and reduces
starch digestibility. The amylose complex was resistant to a-amylase
in vitro. With increasing amylose content, there was a decrease in the
rate of amylolysis after extrusion. When added to high amylose starch,
monoglycerides and linear free fatty acids are more likely to form com-
plexes than do triglycerides and phosphatides (Bhatnagar & Hanna,
1994; Mercier et al., 1980). In general, conditions of low moisture con-
tent, high temperature, high viscosity and longer residence time favor
complex formation in the extruder (Ho & Izzo, 1992).
4.3. Effect of cooling and storage on GI
The amount of resistant starch was increased when boiled potatoes
were stored in a refrigerator (Akerberg et al., 1998). Cold storage of po-
tatoes has been demonstrated to affect the starch bioavailability in vivo
(Garcia-Alonso & Goni, 2000; Leeman et al., 2005). Fernandes et al.
(2005) observed that the consumption of hot red potatoes (GI = 89)
released more blood (40%) glucose than that of cold red potatoes
(GI = 56) and pre-cooked, frozen and reheated before consumption,
French fries gave less GI value than when consumed immediately after
cooking (Table 8). GI of Baked (GI = 72) and roasted white potatoes
(GI = 73) that were consumed immediately after cooking (Wolever
et al., 1994) were more than the baked and boiled white potatoes
(GI = 59–64) that were pre-cooked and reheated (Fernandes et al.,
2005). Similarly, reduction in rapidly digested starch compared to slow-
ly digested starch is observed when cooked and refrigerated compared
to freshly cooked in some varieties of New Zealand potatoes (Table 4).
So precooking and reheating potatoes before consumption will produce
a smaller glycemic response compared with potatoes consumed imme-
diately after cooking. Englyst and Cummings (1987) also suggested that
recurrent heating and coolingresult in more resistant starch that direct-
ly impacts the glycemic response by slowing digestion and absorption.
Tahvonen et al. (2006) reported a significantly smaller GI in cold pota-
toes than the GI of hot-steamed boiled potatoes. The quantity of total
Table 7
Glycemic index⁎of potato with different conventional processing conditions.
Reference Boiled Baked Roasted Mashed French fries Microwave
Foster-Powell & Brand-Miller, 1995 64 53 55 74 38 –
Garcia-Alonso & Goni, 2000 71 48 53 (crisped) 77 40 –
Fernandes et al., 2005 –72 73 88 64 –
Tahvonen et al., 2006 74 ± 28
(fresh)
68 ± 21
(fresh)
76 ± 30
(fresh)
––
Wolever et al., 1994 59–64 –– 88 76 –
Soh & Brand-Miller, 1999 88 ± 9 93 ± 11 91 ± 9 79 ± 9
Foster-Powell et al., 2002 ––– 74–97 ––
⁎Glucose as reference food.
Table 8
Incremental area under curve and glycemic index values for 50 g available carbohydrate portions of white bread and seven potatoes tested in 12 subjects. Adapted from Fernandes et al.
(2005).
Potato tested Area under curve (mmol × min/L) Glycemic index
White bread = 100 Glucose = 100
White bread 174 ± 18
xy
100
xyz
71
xyz
Baked Russet potato 178 ± 25
xy
107.7 ± 12.3
xyz
76.5 ± 8.7
xyz
Instant mashed potato 206 ± 23
x
123.5 ± 11.3
xy
87.7 ± 8.0
xy
Roasted California white potato 165 ± 20
xy
101.8 ± 11.6
xyz
72.3 ± 8.2
xyz
Baked PEI white potato 178 ± 21
xy
102.5 ± 6.4
xyz
72.8 ± 4.5
xyz
Boiled red potato (hot) 208 ± 20
x
125.9 ± 10.1
x
89.4 ± 7.2
x
Boiled red potato (cold) 135 ± 18
y
79.2 ± 7.4
z
56.2 ± 5.3
z
French fried potatoes 155 ± 19
xy
89.6 ± 7.7
yz
63.6 ± 5.5
yz
xyz
Means in the same column with different superscript are significantly different (P b0.05).
PEI—Prince Edward Island.
43B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
digestible starch in the consumable food is responsible for the release of
glucose into blood (Fernandes et al., 2005).
With coolingor storing of potatoes for 24 h, the quantity of initial re-
sistant starch (1.18%) in boiled potatoes increased to 4.63%. Cooling the
outer portion of French fries also affected the overall resistant starch.
Resistant starch observed in the whole sample of French fries (5.16%)
was more than the resistant starch (1.17%) in the internal part only
(Garcia-Alonso & Goni, 2000). The investigator also observed a high
RS content in retrograded potato flours. A comparison of cold vs. hot
red potato consumption on postprandial glucose level (Fig. 5) showed
that cold potatoes elicited nearly a 405 lower response than that of
hot potatoes (Fernandes et al., 2005). For example, 7% resistance starch
in cooked potato increases to about 13% upon cooling (Englyst et al.,
1992). Therefore, cooling boiled potatoes forms resistance starch that
is not digested in the small intestine and does not contribute to blood
glucose response.
5. Summary
The benefits of a low GI food in reducing insulin demand, improving
satiety, improving blood glucose control with diabetic people, reducing
blood lipid level and increasing colonic fermentation are well docu-
mented. Potatoes are a major food item indeveloped countries, and pro-
ducing potato food products with low GI will help to reduce the overall
GI of the diet in these countries. Potato and its products produced vari-
able glycemic responses, depending on potato cultivars, maturity, starch
structure, processing method and extend. GI of potatoes may be signif-
icantly reduced by manipulating the genotype of exotic potato cultivars
and the development of potato genotypes with high amylose content.
Food processing plays an important role inthe control of the GI of potato
products. The GI of potato products can be reduced by optimizing the
food processing conditions. For example, precooking and reheating or
consuming processed potatoes in cold condition may result in reduced
glycemic responses. Conditions known to decrease the digestibility of
potato starch and subsequent GI responses are those which decrease
the starch granule damage and gelatinization, increase lipid–amylose
formation and increase starch retro-gradation during cooling and stor-
age. Human lifestyle and daily activities effect on the type 2 diabetes.
In future, studies on the interactions between exercise, diet, timing of
consumption, conditions of foods and type 2 diabetes related diseases
would be needed to understand the mechanism of glycemic index in
health.
References
Akerberg, A. K. E., Liljeberg,H. G. M., Granfeldt, Y. E.,Drews, A. W., & Bjorck, I.M. E. (1998).
An in vitro method, based on chewing, to predict resistant starch content in foods al-
lows parallel determination of potentially available starch and dietary fiber. Journal of
Nutrition,128,651–660.
Amano, Y., Sugiyama, M., Lee, J.S., Kawakubo, K., Mori, K., Tang, A.C., et al. (2007). Glyce-
mic index-based nutritional education improves blood glucose control in Japanese
adults a randomized controlled trial. Diabetes Care,30,1874–1876.
American Diabetes Association (2002). Evidence-based nutrition principles and recom-
mendations for the treatment and prevention of diabetes and related complications.
Diabetes Care,25,202–212.
Araya, H., Contreras, P., Alvina, M., Vera, G., & Pak, N. (2002). Acomparisonbetweenan
in vitro method to determinecarbohydrate digestion rate and the glycemic response
in young men. European Journal of Clinical Nutrition,56(8), 735–739.
Aston, L. M. (200 6). Glycemic index and metabolic disease risk. Proceedings of the
Nutrition Society,65,125–134.
Augustin, L. S., Dal Maso, L., La Vecchia, C., Parpinel, M., Negri, E., Vaccarella, S., et al.
(2001). Dietary glycemic index and glycemic load, and breast cancer risk: A case–
control study. Annals of Oncology,12,1533–1538.
Augustin, L. S., Franceschi,S., Jenkins, D. J. A.,Kendall, C. W. C., & La Vecchia, C. (2002).Gly-
cemic index in chronic disease: A review. European Journal of Clinical Nutrition,56,
1049–1071.
Augustin, L. S., Gallus, S.,Bosetti, C., Levi, F.,Negri, E., Franceschi, S., et al. (2003). Glycemic
index and glycemic load in endometrial cancer. International Journal of Cancer,105,
404–407.
Barron, C., Buléon, A., Colonna, P., & Della Valle, G. (2000). Structural modification of low
hydrated pea starch subjected to high thermo-mechanical processing. Carbohydrate
Polymers,43,171–181.
Bednar, G. E., Patil, A.R., Murray, S. M., Grieshop, C. M., Merchen, N. R., & Fahey, G. C., Jr.
(2001). Starch and fiber fractions in selected food and feed ingredients affect their
small intestinal digestibility and fermentability and their large bowel fermentability
in vitro in a canine model. Journal of Nutrition,131,276–286.
Bhatnagar, S., & Han na, M.A. (1994). Amylose–lipid complex formation during
single-screw extrusion of various corn starches. Cereal Chemistry,71,582–587.
Biliaderis, C., & Galloway, G. (1989). Crystallization behavior of amylose-V complexes:
Structure–property relationships. Carbohydrate Research,189,31–48.
Bjoerck, I., & Asp, N. G. (1994). Controlling the nutritional properties of starch in foods—
A challenge to the food industry. Trends in Food Science and Technology,5,213–218.
Bjorck, I., Liljeberg, H., & Ostman, E. (2000). Low glycemic-index foods. British Journal of
Nutrition,83(Suppl. 1), S149–S155.
Bjork, J., Nilsson, J., Hultcrantz, R., & Johansson, C. (1993). Growth-regulatory effects of
sensory neuropeptides, epidermal growth factor, insulin, and somatostatin on the
non-transformed intestinal epithelial cell line IEC-6 and the colon cancer cell line
HT 29. Scandinavian Journal of Gastroenterology,28,879–884.
Boden, G., Jadali, F., White, J., Liang, Y., Mozzoli, M., Chen, X., etal. (1991). Effects of fat on
insulin-stimu lated carbohydrate metabolism in normal men. Journal of Clinical
Investigation,88,960–966.
Fig. 5. Bloodglucose response of different varietiesof potatoes (open symbols, dotted lines)calculated from 50 g available carbohydrate portions present compared to whitebread (closed
circle, solid lines). Adapted from Fernandes et al., 2005.
ab
Means at the same time point with different letters are significantly different (P b0.05).
c
PEI—Prince Edward island.
44 B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
Braaten,J. T., Wood, P. J., Scott,F. W., Riedel, K. D., Poste, L. M., & Collins, M. W. (1991). Oat
gum lowers glucose and insulin after an oral glucose load. American Journal of Clinical
Nutrition,53,1425–1430.
Brand, J. C., Nicholson, P. L., Thorburn, A.W., & Truswell, A. S. (1985). Food processing and
the glycemic index. American Journal of Clinical Nutrition,42,1192–1196.
Brand-Miller, J. C. (1994). The importance of glycemic index in diabetes. American Journal
of Clinical Nutrition,59, 747S–752S (Suppl.).
Brand-Miller, J. C., Pang, E., & Bramall, L. R. (1992). A high or low glycemic index food?
American Journal of Clinical Nutrition,56,1034–1036.
Brumovsky, J. O., & Thompson, D. B. (2001). Production of boiling-stable granular resis-
tant starch by partial acid hydrolysis and hydrothermal treatments of highamylose
maize starch. Cereal Chemistry,780,680–689.
Burton-Freeman, B., Davis, P. A., & Schneeman, B. O. (2002). Plasma cholecystokinin is as-
sociated with subjective measures of satiety in women. American Journal of Clinical
Nutrition,76,659–667.
Calle-Pascual, A. L., Gomez, V., Leon, F., & Bordiu, E. (1988). Foods with a low glycemic
index do not improve glycemic control of both type 1 and type 2 diabetic patients
after one month of therapy. Diabetes & Metabolism,14,629–633.
Chung, H.J., Liu, Q., & Hoover,R. (2009). Impactof annealing and heat-moisture treatment
on rapidly digestible, slowly digestible and resistant starch levels in native and
gelatinized corn, pea and lentil starches. Carbohydrate Polymers,75(2009), 436–447.
Chunga, J.,Shinb, D., & Limc, S. (2008). In vitro starch digestibility and estimated glycemic
index of chemical ly modified corn st arches. Food Research International,41(6),
579–585.
Collier, G., & O'Dea, K. (1983). The effect of coingestion of fat on the glucose, insulin, and
gastric inhibitory polypeptide responses to carbohydrate and protein. American Jour-
nal of Clinical Nutrition,37,941–944.
Collins, A., Duthie, S., & Ross, M. (1994). Micronutrients and oxidative stress in the etiol-
ogy of cancer. Proceedings of the Nutrition Society,53,67–75.
Cooke, D., & Gidley, M. J. (1992). Loss of crystalline and molecular order during starch ge-
latinization: Origin of the enthalpic transition. Carbohydrate Research,227,103–112.
Davidson, V. J., Paton, D., Diosady, L., & Rubin, L. J. (1984). A Model for mechanical degra-
dation of wheat s tarch in a single-screw extruder. Journal of Food Sc ience,49,
1154–1157.
Eggum, B. O., Juliano, B. O., Perez, C. M., & Khush, G. S. (1993). Starch, energy, and protein
utilization by rats in milled rice or IR36-based amylose extender mutant. Cereal
Chemistry,70,275–279.
Englyst, H. N., & Cummings, J. H. (1987). Digestion of polysaccharides of potato in the
small intestine of man. American Journal of Clinical Nutrition,45,423–431.
Englyst, K. N., Englyst, H. N., Hudson, G. J., Cole, T. J., & Cummings, J. H. (1999). Rapidly
available glucose in foods: An in vitro measurement that reflects the glycemic re-
sponse. American Journal of Clinical Nutrition,69(3), 448–454.
Englyst, H. N., Kingman, S. M., & Cummings, J. H. (1992). Classification and measurement
of nutritionally important starch fractions. European Journal of Clinica l Nutrition,
46(Suppl. 2), S33–S50.
Englyst, K. N., Liu, S., & Englyst, H. N. (2007). Nutritional characterization and measure-
ment of dietary carbohydrates. European Journal of Clinical Nutrition,61,S19–S39.
FAO/WHO (1998). Carbohydrates in human nutrition: Report of a joint FAO/WHO expert
consultation. FAO Food and Nutrition Paper,66,1–140.
Fernandes, G., Velangi, M., & Wolever, T. (2005). Glycemic index of potatoes commonly
consumed in North America. Journal of the American Di etetic Associa tion,105,
557–562.
Folsom, A.R., Demissie, Z., & Harnack, L. (2003). Glycemic index, glycemic load, and inci-
dence of endometrial cancer: The Iowa women's health study. Nutrition and Cancer,
46,119–124.
Foster-Powell, K., & Brand-Miller, J. C. (1995). International tables of glycemic index.
American Journal of Clinical Nutrition,62,871S–890S.
Foster-Powell,K.,Holt,S.H.A.,&Brand-Miller,J.C.(2002).International tables of gly-
cemic index and glycemic load values. American Journal of Clinical Nutrition,76,
5–56.
Frost, G. S., Keogh, B. E., Smith, D., Leeds, A.R., & Dornhorst, A. (1998). Reduced adipocyte
insulin sensiti vity in Caucasian and Asian subjects with coronary heart disease.
Diabetic Medicine,15,1003–1009.
Garcia-Alonso, A., & Goni, I. (2000). Effect of processing on potato starch: in vitro avail-
ability and glycemic index. Starch,52,81–84.
Gidley, M. J., Cooke, D., Darke, A.H., Hoffmann, R. A., Russell, A. L., & Greenwell, P. (1995).
Molecular order and structure in enzyme-resistant retrograded starch. Carbohydrate
Polymers,28,23–31.
Gilbertson, H. R., Brand-Miller, J. C., Thorburn, A. W., Evans, S., Chondros,P., & Werther, G.
A. (2001). The effect of flexible low glycemic index dietary advice versus measured
carbohydrate exchange diets on glycemic control in children with type 1 diabetes.
Diabetes Care,24, 1137–1143.
Goni, I., Bravo, L., Larrauri, J. A., & Saura-Calixto, F. (1997). Resistant starch in potatoes
deep-fried in olive oil. Food Chemistry,59,269–272.
Goni, I., Garcia-Alonso, A., & Saura-Calixto,F. (1997). A starch hydrolysis procedure to es-
timate glycemic index. Nutrition Research,17(3), 427–437.
Govindasamy, S., Campanella, H., & Oates, C. G. (1996). High moisture twin-screw extru-
sion of sago starch: 1. Influence on granule morphology and structure. Carbohydrate
Polymers,3,215–286.
Granfeldt, Y., Bjorck, I., Drews, A., & Tovar, J. (1992). An in vitro procedure based on
chewing to predict metabolic response to starch in cereal and legume produ cts.
European Journal of Clinical Nutrition,46(9), 649–660.
Gullfford,M. C., Bicknell, E. J., & Scarpello, J. H. (1989). Differential effect of protein and fat
ingestion on blood glucose responses to highand low-glycemic-index carbohydrates
in non insulin-dependent diabetic subjects. American Journal of Clinical Nutrition,50,
773–777.
Gunaratne, A., & Hoover, R. (2002). Effect of heat–moisture treatment on the structure
and physicochemical properties of tuber and root starches. Carbohydrate Polymers,
49,425–437.
Haber, G. B., Heaton, K. W., Murphy, D., & Burroughs, L. F. (1977). Depletion and disrup-
tion of dietary fiber. Effects on satiety, plasma glucose, and serum insulin. Lancet,
8040,679–682.
Haralampu, S. G. (2000). Resistantstarch—A review of the physicalproperties and biolog-
ical impact of RS3. Carbohydrate Polymers,41,285–292.
Henry, C. J. K., Lightowler, H. J., Strik, C. M., & Storey, M. (2005). Glycemic index values for
commercially available potatoes in Great Britain. British Journal of Nutrition,94,917–921.
Ho, C. T., & Izzo, M. T. (1992). Lipid–protein and lipid–carbohydrate interactions during
extrusion. In Kokini Ho, & Karwe (Eds.), Food ext rusion science an d technology
(pp. 415–426). New York: Mercel Dekker.
Hollenbeck, C. B., & Coulston, A.M. (1991).The clinical utility ofthe glycemic index and its
application to mixed meals. Canadian Journal of Physiology and Pharm acology,69,
100–107.
Holm, J., Bjoerck, I., Ostrowska, S., Eliasson, A.C., Asp, N. G., Larsson, K., et al. (1983). Di-
gestibility of amylose–lipid complexes in-vitro and in-vivo. Starch,35,294–297.
Holm, J., Lundquist, I., Bjoerck, I., Eliasson, A.C., & Asp, N. G. (1988). Degree of starch gela-
tinization, digestion rate of starch in vitro, and metabolic response in rats. American
Journal of Clinical Nutrition,47,1010–1016.
Hoover, R., & Manuel, H. (1996). Effect of heat-moisture treatment on the structure and
physicochemical properties of legume starches. Food Research International,29,
731–750.
Hoover, R.,& Vasanthan,T. (1994). Effect of heat-moisture treatment on the structure and
physicochemical properties of cereal, legume, and tuber starches. Carbohydra te
Research,252,33–53.
Huth, M., Dongowski, G., Gebhardt, E., & Flamme, W. (2000). Functional properties of di-
etary fibre enriched extrudates from barley. Journal of Cereal Science,32,115–128.
Institute of Medicine (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat,
fatty acids, cholesterol, protein, and amino acids. USA: National Academics of Sciences.
Jacobs, H.,& Delcour, J. A. (1998). Hydrothermalmodifications of granular starch, with re-
tention of the granular structure:A review. Journal of Agricultural and FoodChemistry,
46,2895–2905.
Jenkins, D. J. A., Wolever, T. M. S., & Collier, G. R. (1987). Metabo lic effects of a
low-glycemic-index diet. American Journal of Clinical Nutrition,46,968–975.
Jenkins, D. J. A., Wolever, T. M. S., Kalmusky, J., Guidici, S., Giordano, C., Patten, R., et al.
(1987). Low-glycemic index diet in hyperlipidemia: Use of traditional starchy
foods. American Journal of Clinical Nutrition,46,66–71.
Jenkins, D. J. A., Wolever, T. M. S., Taylor, R. H., Barker, H. M., Fielden, H., Baldwin, J. M.,
et al. (1981). Glycemic index of foods: A physiological basis for carbohydrate ex-
change. American Journal of Clinical Nutrition,34,362–366.
Karlsson, M. E., & Eliasson, A.C. (2003). Gelatiniz ation and retrogradation of potato
(Solanum tuberosum) starch in situ as assessed by differential scanning calorimetry
(DSC). LWT—Food Science and Technology,36,735–741.
Kingman,S. M., & Englyst, H. N. (1994). The influence of food preparation methodson the
in-vitro digestibility of starch in potatoes. Food Chemistry,49(2), 181–186.
Larsen, H. N., Rasmussen, O. W., Rasmussen, P. H., Alstrup, K. K., Biswas, S. K., Tetens, I.,
et al. (2000). Glycemic index of parboiled rice depends on the severity of processing:
study in type 2 diabetic subjects. European Journal of Clinical Nutrition,54,380
–385.
Leeman, A.M., Barstroem, L. M., & Bjoerck, I. M. E. (2005). In vitro availability of starch in
heat-treated potatoes as related to genotype, weight and storage time. Journal of the
Science of Food and Agriculture,85,751–756.
Lehmann, U., & Robin, F. (2007). Slowly digestible starch—Its structu re and health impli-
cations: A review. Trends in Food Science and Technology,18,346–355.
Lightowler, H. J., & Henry, C. J. K. (2009). Glycemic response of mashed potato containing
high-viscosity hydroxypropylmethylcellulose. Nutrition Research,29(8), 551–557.
Liljeberg, H., & Bjorck, I. (1998). Delayed gastric emptying rate may explain improved
glycaemiain healthy subjects to a starchy meal with added vinegar. European Journal
of Clinical Nutrition,52(5), 368–371.
Ludwig, D. S. (2002). The glycemic index: physiological mechanisms relating to obesity,
diabetes, and cardiovascular disease. Journal of American Medical Association,287,
2414–2423.
Lunetta, M., Di Mauro, M., Crimi,S., & Mughini, L. (1995).No important differences in gly-
cemic responses to common fruits in type 2 diabetic patients. Diabetic Medicine,12,
674–678.
Lynch, D., Liu, Q., Tarn, T. R., Bizimungu, B., Chen, Q., Harris, P., et al. (2007). Glycemic
index—A review and implications for the potato industry. American Journal of Potato
Research,84(2), 179–190.
Ma, Y., Li, Y., Chiriboga, D. E., Olendzki, B. C., Hebert, J. R., Li, W., et al. (2006). Association
between carbohydrate intake and serum lipids. Journal of th e American College of
Nutrition,25,155–163.
Magaletta, R. L., DiCataldo, S. N., Liu, D., Li, H. L., Borwankar, R. P., & Martini,M. C. (2010).
In vitro method for predicting glycemic index of foods using simulated digestion and
an artificial neural network. Cereal Chemistry,87(4), 363–369.
Maki, K. C., Rains, T. M., Kaden, V. N., Raneri, K. R., & Davidson, M. H. (2007). Effects of a
reduced-glycemic-load diet on body weight, body composition, and cardiovascular
disease risk markers in ov erweight and obese adults. American Journal of Clinical
Nutrition,85,724–734.
Mercier, C., Charbonniere, R., Gallant, D., & Guilbot, A. (1979). Structural modification
of various starches by extrusion cooking with a twin-screw French extruder.
Easter School in Agricultural Scien ce, University of Nottingham, [Proceedings], 27th
(polysaccharides food) (pp. 153–170).
Mercier, C., Charbonniere,R., Grebaut, J., & De la Gueriviere, J. F. (1980). Formation of am-
ylose–lipid complexes by twin-screw extrusion cooking of manioc starch. Cereal
Chemistry,57,4–9.
45B. Nayak et al. / Food Research International 56 (2014) 35–46
Author's personal copy
Michels,K. B., Mohllajee, A. P., Roset-bahmanyar,E., Beehler, G. P., & Moysich, K. P. (2007).
Diet and breast cancer. A review of the prospective observational studies. Cancer,
109(12, Suppl.), 2712–2749.
Monro, J.,Mishra, S., Blandford, E., Anderson, J., & Genet,R. (2009). Potato genotype differ-
ences in nutritionally distinct starch fractions after cooking, and cooking plus storing
cool. Journal of Food Composition and Analysis,22(6), 539–545.
Nakazawa, Y., & Wang, Y. J. (2003). Acid hydrolysis of native and annealed starches and
branch-structure of their Naegeli dextrins. Carbohydrate Research,338,2871–2882.
National Potato Council, United States of America (2013). Potato facts. Retrieved on Au-
gust 25, 2013 at. www.nationalpotatocouncil.org
Parada, J., & Aguilera, J. M. (2009). In-vitro digestibility and glycemic response of potato
starch is related to granule size and degree of gelatinization. Journal of Food Science,
74(1), E34–E38.
Parchure, A. A., & Kulkarni, P. R. (1997). Effect of food processing treatments on genera-
tion of resistant starch. International Journal of Food Sciences and Nutrition,48,
257–260.
Pawlak, D. B., Ebbeling, C. B., & Ludwig, D. S. (2002). Should obese patients be counseled
to follow a low-glycemic index diet? Yes. Obesity Reviews,3,235–243.
Piatti, P.M., Monti, L. D., Pacchioni, M., Pontiroli, A. E., & Pozza, G. (1991). Forearm insulin-
and non-insulin-mediated glucose uptake and muscle metabolism in man: role of
free fatty acids and blood glucose levels. Metabolism,40,926–933.
Politz, M. L., Timpa, J.D., & Wasserman, B. P. (1994). Quantitative measurement of extru-
sion -induced starch fragmentation products in maize flour using nonaqueous auto-
mated gel-permeation chromatography. Cereal Chemistry,71,532–536.
Raben, A., Kiens, B., & Richter, E. A. (1994). Differences in glycaemia, hormonal response
and energy expenditure after a meal rich in mono- and disaccharides compared to
a meal rich in polysaccharides in physically fit and sedentary subjects. Clinical
Physiology,14,267–280.
Regina, A., Bird, A., Topping, D., Bow den, S., Freeman, J., Barsby, T., et al. (2006).
High-amylose wheat generated by RNA interference improves indices of
large-bowel heal th in rats. Proceedi ngs of the National Academy of Sciences of the
United States of America,103,3546–3551.
Riccardi, G., Rivellese, A. A., & Giacco, R. (2008). Roleof glycemic index and glycemic load
in the healthy state, in prediabetes, and in diabetes. American Journal of Clinical Nutri-
tion,87, 269S–274S (Suppl.).
Ring, S. G., Gee, J. M., Whittam, M., Orford, P., & Johnson, I. T. (1988). Resistant starch: its
chemical form in foodstuffs and effect on digestibility in vitro. Food Chemistry,28,
97–109.
Sagar, A.D., & Merrill, E. W. (1995). Starch fragmentation during extrusion processing.
Polymer,36,1883–1886.
Sajilata, M. G., Singhal, R. S., & Kulkarni, P. R. (2006). Resistant starch—A review.
Comprehensive Reviews in Food Science and Food Safety,5,1–17.
Schafer, G., Schenk, U., Ritzel, U., Ranmdori, G., & Leonhardt, U. (2003). Comparison of the
effects of dried peas with those of potatoes in nfixed meals on postprandial glucose
and insulin concentrations in pa tients with type 2 diabetes. Ameri can Journal of
Clinical Nutrition,78,99–103.
Scheppach, W., Fabian, C., Ahrens, F., Spengler, M., & Kasper, H. (1988). Effect of starch
malabsorption on colonic function and metabolism in humans. Gastroenterology,95,
1549–1555.
Schwall, G.P., Safford, R., Westcott, R.J., Jeffcoat, R., Tayal, A., Shi, Y., et al. (2000). Produc-
tion of very-high-amylose potato starch by inhibition of SBE A and B. Nature
Biotechnology,18,551–554.
Shin, S. I., Kim, H. J., Ha, H. J., Lee, S. H., & Moon, T. W. (2005). Effect of hydrothermal
treatment on formation and structural characteristics of slowly digestible nonpasted
granular sweet potato starch. Starch-Starke,57,421–430.
Silvera, S. A., Rohan, T. E., Jain, M., Terry, P. D., Howe, G. R., & Miller, A.B. (2005). Glycemic
index, glycemic load and risk of endometrial cancer: A prospective cohort study.
Public Health Nutrition,8,912–919.
Soh, N. L., & Brand-Miller, J. (199 9). The glycemic index of potatoe s: The effect of
variety, cooking method and maturity. European Journal of Clin ical Nutrition,53,
249–254.
Solomon, T. P. J., & Thyfault, J. P. (2013). Type 2 diabetes sits in a chair. Diabetes, Obesity
and Metabolism,15,987–992.
Sugiyama, M., Tang, A.C., Wakaki, Y., & Koyama, W. (2003). Glycemic index of single and
mixed meal foods among common Japanese foods with white rice as a reference
food. European Journal of Clinical Nutrition,57,743–752.
Tahvonen, R., Hietanen, R. M., Sihvonen, J., & Salminen, E. (2006). Influence of different
processing methods on the glycemic ind ex of potato. Journal of Food Composition
and Analysis,19,372–378.
Tester, R. F., & Debon, J. J. (2000). Annealing of starch—Areview.International Journal of
Biological Macromolecules,27,1–12.
Theander, O., & We sterlund, E. (19 87). Studies on chemical modifications in
heat-processed starch and wheat flour. Starch,39,88–93.
Thorburn, A.W., Brand, J. C., O'Dea, K., Spargo, R. M., & Truswell, A. S. (1987). Plasma glu-
cose and insulin responses to starchy foods in Australian aborigines: A population
now at high risk of diabetes. American Journal of Clinical Nutrition,46,282–285.
Thorburn, A. W., Brand, J. C., & Truswell, A. S. (1987). Slowly digested and absorbed car-
bohydrate in traditional bush foods: a protective factor against diabetes? American
Journal of Clinical Nutrition,45,98–106.
Tran, T. T., Medline, A., & Bruce, R. W. (1996). Insulin promotion of colon tumors in rats.
Cancer Epidemiology, Biomarkers and Prevention,5, 1013–1015.
United States Department of Agriculture, Economic Research Service (2013). Food avail-
ability (percapita) data system. Retrieved on November 19, 2013 at. http://www.ers.
usda.gov
Unlu, E., & Faller, J. F. (1998). Formation of resistant starch by a twin-screw extruder.
Cereal Chemistry,75,346–350.
Vaaler, S., Hanssen, K. F., & Aagenaes, O. (1984). The effect of cooking upon the blood glu-
cose response to ingested carrots and potatoes. Diabetes Care,7,221
–223.
van den Einde, R. M., Akkermans, C., van der Goot, A. J., & Boom, R. M. (2004). Molecular
breakdown of corn starch by thermal and mechanical effects. Carbohydrate Polymers,
56,415–422.
Vasanthan, T., & Bhatty, R. S. (1998). Enhanceme nt of resistant starch (RS3) in
amylomaize, barley, field pea and lentil starches. Starch,50,286–291.
Venn, B. J., & Green, T. J. (2007). Glycemic index and glycemic load: measurement issues
and their effect on diet–disease relationships. European Journal of Clinical Nutrition,
61(S1), S122–S131.
Welty, F. K. (2013). How do elevated triglycerides and low HDL-cholesterol affect inflam-
mation and atherothrombosis? Current Cardiology Reports,15(400), 1–13.
Willett, W.C., Manson, J., & Liu, S. (2002). Glycemic index,glycemic load, and risk of type
2 diabete s. American Journal of Clinical Nutrition,76,274S–279S (Suppl.).
Wolever, T. M. S. (1990). Glycemic index and mixed meals. American Journal of Clinical
Nutrition,51, 1113–1114.
Wolever, T. M. S., & Mehling, C. (2003). Long-term effect of varying the source or amount
of dietary carbohydrate on postprandial plasma glucose, insulin, triacylgiycerol, and
free fatty acid concentrations in subjects with impaired glucose tolerance. American
Journal of Clinical Nutrition,77,612–621.
Wolever, T. M. S., Jenkins, D. J. A., Jenkins, A. L., & Josse, R. G. (1991). The glycemic index:
Methodology and clinical implic ations. America n Journal of Clinical Nutrition,54,
846–854.
Wolever,T.M.S.,Jenkins,D.J.A.,Ocana,A.M.,Rao,V.A.,&Comer,G.R.(1988).
Second-meal effect: Low glycemic index foods eaten at dinner improve subse-
quent breakfast glycemic response. American Journal of Clinical Nutrition,48,
1041–1047.
Wolever, T. M. S., Katzman-Relle, L., Jenkins, A. L., Vuksan, V., Josse, R. G., & David, J. A.
(1994). Glycemic index of 102complex carbohydratefoods in patients with diabetes.
Nutrition Research,14,651–669.
46 B. Nayak et al. / Food Research International 56 (2014) 35–46
