SINGLE KERNEL CHARACTERIZATION OF WHEAT VARIETIES IN RELATION TO MILLING QUALITY

Abstract

Single kernel characterization system swiftly measures important physical characteristics of wheat grain and provides forecast for milling quality. Two wheat varieties were tested from SKCS for physical grain parameters. Wheat variety AS 2002 showed higher mean score for kernel weight (32.79mg/kernel), kernel diameter (2.77mm) and seed length (6.47mm) than Inqulab 91 (30.04mg/kernel, 2.65mm and 5.93mm repectively for kernel weight, diameter and length). Kernel density (1.61 mg/mm 3) and SKCS hardness index (85.65) was comparatively greater in Inqulab 91 than AS 2002 (1.54mg/mm 3 , 75.51, respectively). AS-2002 exhibited higher break (139.50g/kg), straight grade flour (681g/kg) yield and milling score (83.28) as compared to Inqulab 91 (107.50g/kg) break, (658.50g/Kg) SGF and (75.19) whereas reduction flour higher in Inqulab 91 (551g/kg) than AS 02 (541.50g/kg). Mean scores for moisture content, ash content, fat content, protein content, crude fiber and NFE ranged from 9.52 to 12.10, 0.84 to 1.14, 1.95 to 3.75%, 9.54 to 13.25%, 0.12 to 7.53% and 63.29 to 76.78% respectively in different milled fractions of both wheat varieties. Break flour yield showed significant correlation with physical grain characteristics like TKW (r=0.97), kernel diameter (r=0.99), milling score (r=0.99), seed length (r=1.00) and SKCS kernel weight (r=0.92) whereas SKCS hardness (r=-0.60) and kernel density (r=-0.54) were negatively associated with break flour. Wheat variety with greater TKW, SKCS KW, kernel diameter and seed length yield more break flour and higher milling score. However, such wheat variety had less SKCS hardness and kernel density.

Full text

136
J. Glob. Innov. Agric. Soc. Sci., 2015, 3(4): 136-141.
ISSN (Online): 2311-3839; ISSN (Print): 2312-5225
DOI:10.17957/JGIASS/3.4.722
http://www.jgiass.com
SINGLE KERNEL CHARACTERIZATION OF WHEAT VARIETIES IN
RELATION TO MILLING QUALITY
Zafar Iqbal1,*, Imran Pasha2, Muhammad Abrar3, Atta Muhammad Arif4 and Sharoon Masih5
1Mango Research Institute, Multan, Pakistan, 2 National Institute of Food Science and Technology, University of
Agriculture, Faisalabad, Pakistan, 3 Wheat Research Institute, Ayub Agricultural Research Institute, Faisalabad,
Pakistan, 4Citrus Research Institute, Sargodha, Pakistan, 5 Food Technology Section, Post-Harvest Research Institute,
Ayub Agricultural Research Institute, Faisalabad, Pakistan
*Corresponding author’s e-mail: zafarft@yahoo.co.in
Single kernel characterization system swiftly measures important physical characteristics of wheat grain and provides
forecast for milling quality. Two wheat varieties were tested from SKCS for physical grain parameters. Wheat variety AS
2002 showed higher mean score for kernel weight (32.79mg/kernel), kernel diameter (2.77mm) and seed length (6.47mm)
than Inqulab 91 (30.04mg/kernel, 2.65mm and 5.93mm repectively for kernel weight, diameter and length). Kernel density
(1.61 mg/mm3) and SKCS hardness index (85.65) was comparatively greater in Inqulab 91 than AS 2002 (1.54mg/mm3,
75.51, respectively). AS-2002 exhibited higher break (139.50g/kg), straight grade flour (681g/kg) yield and milling score
(83.28) as compared to Inqulab 91 (107.50g/kg) break, (658.50g/Kg) SGF and (75.19) whereas reduction flour higher in
Inqulab 91 (551g/kg) than AS 02 (541.50g/kg). Mean scores for moisture content, ash content, fat content, protein content,
crude fiber and NFE ranged from 9.52 to 12.10, 0.84 to 1.14, 1.95 to 3.75%, 9.54 to 13.25%, 0.12 to 7.53% and 63.29 to
76.78% respectively in different milled fractions of both wheat varieties. Break flour yield showed significant correlation
with physical grain characteristics like TKW (r=0.97), kernel diameter (r=0.99), milling score (r=0.99), seed length
(r=1.00) and SKCS kernel weight (r=0.92) whereas SKCS hardness (r=-0.60) and kernel density (r=-0.54) were negatively
associated with break flour. Wheat variety with greater TKW, SKCS KW, kernel diameter and seed length yield more
break flour and higher milling score. However, such wheat variety had less SKCS hardness and kernel density.
Keywords: Chemical composition, Mill streams, quality, Single kernel characterization
INTRODUCTION
Traditional flour milling process produces refined flour.
Prime objective of milling is to separate endosperm without
contamination of outer parts of grain especially bran and
germ (Belderok, 2000; Edwards, 2010). During this process,
the bran and germ layers of grain are removed in order to
stabilize the raw material and increase the keeping quality
(Fiˇsteˇ et al., 2014). Dry milling alters the nature and
upsurges the edibility of products obtained from cereals
(Delcour et al., 2012). Dry milling of wheat results in
production of flour, bran and wheat germ (OECD, 2003).
Refined flour thus obtained is more acceptable and relishing
food raw material (Delcour et al., 2012). However, with
increase in palatability, the nutritive value of refined flour
decreases (Delcour and Hoseney, 2010). Knowledge of
kernel parameters can help in improving milling yields
(Edwards, 2010). Milling behavior is predicted on the basis
of many factors (Bechtel et al., 2009). Small improvements
in flour yield are possible by manipulation of these factors.
Hardness and softness are the milling characteristics related
to breakage pattern of endosperm (Hrušková and Švec,
2009). The wheat hardness is strongly associated with the
semolina and flour yields (Hrušková et al. 2008). However,
Vignaux et al. (2004) reported hardness as possible cause
for reduction in flour yield. Soft-textured wheat genotypes
(Pina-D1a/Pinb-D1d) showed the least value for grain
hardness and higher break flour and lesser reduction flour
yield (Ma et al., 2009). Wheat lines with Pinb-D1b allele
showed significant reduction in grain hardness, higher break
flour yield and milling score and lower flour ash content
than the Pina-D1b group (Martin et al. 2001, 2008). Pina-
D1a/Pinb-D1b genotypes displayed better milling yield than
Pina-D1b/Pinb-D1a (Eagles et al., 2006). Endosperm
texture affects milling characteristics (Ramseyer et al.,
2011).
Milling performance is a complex quality parameter with
kernel hardness being a highly significant component
(Edwards, 2010). Milling efficiency is measured in terms of
the purity of kernel fractions obtained at each step during
milling (OECD, 2003). Commercial flour mills obtain
refined flour as 80% of wheat kernel while remaining 20%
is utilized for animal feed and dietary fiber for human foods
(Orth and Shellenberger 1988). Wheat varieties possessing
distinctive bolting and sifting characteristics with typical
flour recovery and ash content exhibit good milling quality
(Maghirang et al., 2006). Milling score elucidates yield and
ash content of flour and integrates it with break flour yield
(Morris et al., 2004). Hard red spring (HRS) wheat showed
more total flour and milling score than hard red winter
(HRW) wheat. Moreover, HRS exhibited less break flour
than HRW wheat (Maghirang et al., 2006).

Iqbal, Pasha, Abrar, Arif & Masih
137
Hardness Index measured from Single Kernel
Characterization System (SKCS) is an arbitrary scale. It
shows a histogram of the distribution of the hardness index
values for 300 grains (Edwards, 2010). SKCS 4100 system
provides rapid measurements of wheat physical properties
important to miller for direct prediction of processing
quality (Osborne and Anderssen, 2003). SKCS is the most
suitable indicator of milling quality for small sample
quantities (Edwards, 2010). Value of hardness index in
SKCS is outcome of deformation curve resulting from force
applied for grinding of individual kernels. Wheat grain
moisture, kernel size and kernel weight are main factors
affecting crushing force (Martin et al., 1993). Kernel
hardness in wheat can be quantified by either NIR, SKCS
hardness index and break flour yield (Morris et al., 1999).
Characteristics of wheat kernel are decisive factor in both
the milling quality and final end-use of food wheat
(Hrušková and Švec, 2009). Test weight measures bulk
density of grain, envisages the grain size and used as rough
indicator of flour yield potential of wheat varieties
(Edwards, 2010; Khan et al., 2009). Higher sizing yield is
favorable for a high yield of low ash flour (Li and Posner,
1989). The 1000 kernel weight is a useful tool for the
assessment of the potential milling yield. The kernel size
contributes directly towards the improvement of grain as
well as milling yield. The wheat varieties with more grain
weight showed better milling yield (Khan et al., 2009).
Flour milling alters the microstructure of the intact
endosperm tissue (Souza et al., 2011). Wheat producing
flour with low ash at high extraction rates possess good
milling quality (Posner and Hibbs 1997). Ash content
indicates milling performance by indirectly revealing the
amount of bran contamination. Ash can affect color,
imparting a darker color to finished products (Keran et al.,
2009). Current study was planned to investigate milling
performance of wheat varieties and its relation with physical
characteristics of grain and chemical composition of flour.
MATERIALS AND METHODS
Wheat Milling: Two commercially available wheat varieties
i.e. Inqulab-91 and AS-2002 were used as medium of
experiment. Perten SKCS 4100 (Perten Instruments,
Springfield, IL) was used to measure single kernel grain
hardness, moisture content and diameter according to
Approved Method 55-31 (AACC, 2002) on 300-kernels as
described by Ma et al,. (2009). Clean wheat grains were
tempered at 15.50% moisture content and kept in plastic
containers at room temperature for 24 hours. Water quantity
was calculated by AACC (2000) method No. 26-95. Wheat
was milled through Brabender Quadrumate Senior Mill
(C.W. Brabender Instruments, Inc.) following AACC (2000)
method No. 26-95 to obtain different milling fractions i.e.
break, reduction flour, bran and shorts. Percent yield of
break, reduction flour, bran and shorts were calculated
based on weight recovered of each product divided by total
material recovered according to AACC (2000) method No.
26-21A. Percent recovery of straight grade flour was
determined from combined yield of both break and
reductions flours divided by total weight of all products,
times 100 (Morris et al., 2004). All tests were conducted on
straight-grade flour. Milling score was calculated by method
developed by Martin et al. (2007).
[{100 - [0.50 × (16 - percent temper level) + (80 - flour
yield) + 50 × (Percent flour ash - 0.30)]} × 1.117] - 3.675
Statistical analysis: The data obtained for each parameter
were subjected to statistical analysis to work out effect of
wheat varieties on SKCS parameters, milling fractions yield
and chemical composition by using completely randomized
design and mean values were compared according to
Duncans Multiple Range test (Steel et al., 1997).
RESULTS AND DISCUSSION
SKCS characteristics: Wheat variety AS 2002 with lower
hardness index (75.51) represented higher break flour yield
than Inqulab 91 having greater score for hardness index
(85.65). SKCS hardness index showed insignificant
relationship with break flour yield and explained only 27.90
percent variation in break flour yield. In regression analysis
SKCS hardness could not provide valuable prediction of
break flour yield, however Hogg et al., (2005) revealed that
SKCS kernel hardness might be a larger factor for
predicting break flour. Ma et al. (2009) recorded hardness
index 67.9 to 75.5 in seven near isogenic lines of wheat
while 6.4 to 73.7 in Hi-line Hard red spring wheat and
transgenic isolines (Martin et al., 2008). Based on SKCS
hardness classification, both wheat varieties in current
studies are of medium hard type. Hard wheats have SKCS
hardness scores greater than 50 while soft wheats have
scores less than 50 (Edwards, 2010). Wheat variety AS-
2002 having less mass to diameter3 ratio (1.54mg/mm3)
exhibited significant higher break flour yield than Inqulab
91 (1.61 mg/mm3). Mean for kernel density in current
studies is lower than Souza et al., (2011) who reported
SKCS mass/dia3 vary from 1.88 to 2.39mg/mm3. Ratio of
mass to diameter3 (kernel density) alone elucidated over
50% variation in break flour yield and its value in SKCS
forecasts break flour yield (Campbell et al 2007).
Mean value for kernel weight was significantly higher in
wheat variety AS-2002 (32.79mg/kernel) as compared to
Inqulab 91 (30.04mg/kernel). SKCS kernel weight ranged
from 33.6 to 35.4mg/kernel in Hi-line Hard red spring wheat
and transgenic isolines (Martin et al., 2008) and 34.9-
35.3mm (Martin et al., 2007). Souza et al. (2011) recoded
mean for SKCS kernel weight in range of 29.1mm to
37.4mm in different wheat varieties. Diameter of single
kernel measured from SKCS was considerably higher for
AS-2002 (2.77mm) than Inqulab 91 (2.65mm). Martin et al.
(2007) reported SKCS kernel diameter with lower mean
(2.41-2.45mm) than current studies which might be due to
different genetic make up of wheat varieties. Wheat variety
AS 2002 exhibited significant higher seed length (6.47mm)
than Inqulab 91 (5.93mm). Mean values for seed length in
present investigation are in accordance with findings (5.54-
6.29mm) of Souza et al., (2011). Seed length, kernel

Varieties in relation to milling quality
138
diameter and kernel weight illustrated inverse relationship
with break flour yield. The results of current studies are
contradictory to those reported by Souza et al., (2011). This
might me due to different wheat varieties,tempering and
milling conditions and different mill type as quadrumate
senior is used in current in opposition to Malto Miag in their
studies. Inverse relationship between flour protein contents
and kernel weights or sizes (Park and Chang, 2007).
Milling fractions yield: Wheat varieties showed significant
impact on flour yield. Break flour yield was significantly
higher for AS 02 (139.50g/kg) as compared to Inqulab 91
(107.50g/kg) while it was reverse in case of reduction flour
(Fig. 1) i.e. higher in Inqulab 91 (551g/kg) than AS 02
(541.50g/kg). Straight grade flour yield for was higher for
AS 02 (681g/kg) as compared to Inqulab 91 (658.50g/Kg)
which might be due to difference in tempering requirements
for hard and soft wheats. Martin et al., (2007) reported
higher break (430g/Kg) and total flour yield (674g/Kg) in
soft wheat as compared to hard wheat varieties with
387g/Kg break flour and 661g/Kg total flour yield. Mean
values for break in our studies are similar to Anjum et al.
(1993) (65.7 to 70.00%), Ma et al. (2009) (12.4 to 15.5%)
and Randhawa et al. (2002) (11.41 to 19.72%) while lower
than Souza et al. (2011) who recorded break flour yield
from 20.3 to 25.5g/100g in soft red winter and soft white
winter wheats. Hard NILs yield more flour at break stage
than reduction stage (Greffeuille et al., 2006). The
difference might be due difference in wheat varieties and
type of mill or tempering conditions. Mean score for
reduction flour in current studies is higher than Ma et al.
(2009) (61.0 to 63.2%) and Randhawa et al. (2002) (40.88-
54.21%). This migh be due to different wheat varieties,
tempering moisture content and mill type and settings.
Means for SGF in current investigation are in line with
Randhawa et al. (2002) SGF in range of 52.79 to 70.00%
and Morris et al., (2004) 67.4 to 70.00% while lower than
Souza et al., (2011) who recorded straight grade flour yield
from 71.6 to 76.5g/100g in soft red winter and soft white
winter wheats. The difference is due to different type of mill
used. Maghirang et al. (2006) recorded significantly higher
flour yield for HRS wheat (67.0%) than to HRW wheat
(65.9%). Higher flour yields may result from kernels with
higher endosperm weight (Edwards, 2010). Larger wheat
kernels produce higher break releases (Li and Posner, 1987).
Soft wheat gives almost the same percentage of break and
reduction flour whereas break flour forms only quarter of
the reduction flours yield in hard wheat (Edwards, 2010).
Table 1. Milling yield of different flour fractions of wheat varieties
Wheat Varieties Break Flour (%) Reduction Flour (%) SGF (%) Bran (%) Shorts (%) Milling score
Inqulab-91 10.75±0.80b 55.10±0.42a 65.85±0.57b 33.49±1.18a 5.62±0.24a 75.19±1.24b
AS 2002 13.95±0.80a 54.15±0.42a 68.10±0.57a 28.45±1.18b 4.64±0.24b 83.28±1.24a
LSD (0.05) 2.27 2.27 1.70 2.27 0.57 2.27
SD 1.97 1.04 1.40 2.90 0.58 3.04
Table 2. SKCS quality parameters of wheat varieties
Wheat
varieties
Moisture
content (%)
Kernel
hardness index
SKCS Kernel
weight (mg/kernel)
SKCS
Diameter (mm)
Seed
length (mm)
Kernel density
mass/dia3 (mg/mm3)
Inqulab 91 11.31±0.40a 85.65±2.52a 30.04±0.63b 2.65±0.03b 5.93±0.13b 1.61±0.02a
AS-2002 11.98±0.40a 75.51±2.52b 32.79±0.63a 2.77±0.03a 6.47±0.13a 1.54±0.02b
LSD (0.05) 2.27 6.8 0.9 0.11 0.34 0.06
SD 0.27 13.49 7.51 0.3 0.32 0.04
Table 3. Chemical characteristics of mill streams of wheat variety AS 2002
Milling Fractions Moisture content
(%)
Ash content
(%)
Fat content
(%)
Protein content
(%)
Fiber content
(%)
NFE content
(%)
Break Flour 10.90±0.20ab 0.84±0.06b 2.96±0.19ab 10.57±0.32c 0.12±0.77e 74.62±1.21ab
Red. Flour 10.30±0.20bc 0.57±0.06c 2.69±0.19bc 9.54±0.32d 0.15±0.77d 76.78±1.21a
SGF 9.52±0.20c 0.50±0.06c 1.95±0.19c 11.46±0.32b 0.14±0.77c 76.41±1.21a
Bran 11.35±0.20a 1.05±0.06a 2.65±0.19bc 12.54±0.32a 7.53±0.77a 64.89±1.21c
Shorts 11.00±0.20ab 0.60±0.06c 3.75±0.19a 9.57±0.32d 2.84±0.77b 72.26±1.21b
LSD (0.05) 0.91 0.18 0.91 0.64 0.02 2.66
SD 0.79 0.23 0.73 1.23 2.98 4.67
Table 4. Chemical characteristics of mill streams of wheat variety Inqulab 91
Milling Fractions Moisture content
(%)
Ash content
(%)
Fat content
(%)
Protein content
(%)
Fiber content
(%)
NFE content
(%)
Break Flour 11.75±0.18ab 0.92±0.05b 3.33±0.13b 11.13±0.35c 0.12±0.75d 72.77±1.11b
Red. Flour 11.60±0.18b 0.69±0.05c 2.85±0.13c 9.98±0.35d 0.14±0.75c 74.75±1.11a
SGF 10.23±0.18c 0.60±0.05c 2.96±0.13bc 12.45±0.35b 0.13±0.75cd 73.64±1.11ab
Bran 12.10±0.18a 1.14±0.05a 2.88±0.13bc 13.25±0.35a 7.35±0.75a 63.29±1.11d
Shorts 11.65±0.18ab 0.68±0.05c 4.00±0.13a 10.11±0.35d 2.61±0.75b 70.96±1.11c
LSD (0.05) 0.45 0.14 0.45 0.64 0.02 1.70
SD 0.70 0.21 0.50 1.36 2.91 4.30

Iqbal, Pasha, Abrar, Arif & Masih
139
Table 5. Correlation coefficients physico-chemical and milling characteristics of wheat varieties
Parameters Break
Flour
NIR
hard PSI Red.
Flour SGF TKW TW Ash KD SKCS
hard
K.
Den. MS SL SKCS
KW
NIR Hard 0.55
PSI 0.53 1.00
Red. Flour -0.06 0.81 0.81
SGF 1.00 0.57 0.56 -0.03
TKW 0.97 0.34 0.33 -0.28 0.97
TW 0.54 1.00 1.00 0.81 0.56 0.34
Ash -0.40 0.55 0.56 0.94 -0.38 -0.60 0.55
KD 0.99 0.65 0.64 0.07 1.00 0.94 0.64 -0.28
SKCS Hard -0.60 0.34 0.35 0.83 -0.58 -0.77 0.34 0.97 -0.50
Ker. Den. -0.54 0.41 0.42 0.87 -0.52 -0.72 0.41 0.99 -0.43 1.00
MS 0.99 0.39 0.38 -0.23 0.98 1.00 0.39 -0.55 0.96 -0.73 -0.68
SL 1.00 0.51 0.49 -0.10 1.00 0.98 0.50 -0.44 0.99 -0.64 -0.58 0.99
SKCS KW 0.97 0.32 0.30 -0.30 0.96 1.00 0.31 -0.62 0.93 -0.78 -0.73 0.99 0.98
Protein -0.08 0.79 0.80 1.00 -0.06 -0.31 0.79 0.95 0.04 0.84 0.88 -0.25 -0.13 -0.33
NIR Hard= NIR hardness; Red. Flour=Reduction flour PSI=Particle Size Index; SGF=Straight grade flour TKW=Thousand kernel weight;
TW=Test Weight; KD=Kernel Diameter; SKCS Hard. =SKCS hardness, K. Den. =Kernel Density; MS=Milling Score; SL=Seed length;
SKCS KW= SKCS kernel weight
Wheat variety Inqulab 91 (5.62%) showed higher mean for
shorts than AS 2002 (4.64%). Randhawa et al. (2002)
recorded similar yield of shorts (3.01 to 5.89%). Mean value
for bran was significantly higher in Inqulab 91 as compared
to AS 2002. The amount of bran from Quadrumate senior
mill ranged from 28.48 to 47.45% (Randhawa et al. 2002).
Mean value for milling score was higher for wheat variety
AS 2002 (83.28) as compared to Inqulab 91 (75.19). Martin
et al., (2007) reported similar results for hard PinA-D1b
(80.00) and soft PinB-D1b (82.40) wheats. Hard wheats
exhibit more ash content and less flour yield resulting
decrease in milling score than soft wheats. Morris et al.
(2004) recorded 84.3 to 85.8 milling score in soft wheat
varieties which support the findings of current studies.
Chemical composition of milling fractions: Mean value
for moisture content ranged from 9.52 to 12.10 in different
milling fraction of wheat varieties. Maximum mean for
moisture was recorded in bran (12.10, 11.35) while
minimum in SGF (10.23, 9.52) respectively for Inqulab 91
and AS-2002. Mean for ash content varied between 1.05 to
1.14, 0.50 to 0.68, 0.84-0.92, 0.57 to 0.69, 0.50-0.60%
respectively in bran, shorts, break, reduction and straight
grade flours which are well supported by findings of Saeed
et al. (2011). Fat content of different milled fraction assorted
between 3.75-4.00, 2.65 to 2.88, 2.96-3.33, 2.69-2.85, 1.95-
2.96% respectively in shorts, bran, break, reduction and
straight grade flours. Shorts exhibit higher mean for fat
content while lowest value recorded in SGF. Statistical
mean values for protein concentration of wheat varieties
ranged between 12.54-13.25, 9.57-10.11, 10.57-11.13, 9.54-
9.98, and 11.45-12.46% respectively for bran, shorts, break,
reduction and straight grade flours. The range of means for
crude fiber content varied between 7.35 to 7.53, 2.61 to
2.84, 0.12, 0.14-0.15, 0.13-0.14 respectively in bran, shorts,
break, reduction and SGF flours. NFE content in different
milling fractions differed from 74.75 to 76.78, 73.64 to
76.41, 72.77 to 74.62, 70.96 to 72.26 and 63.29 to 64.89%
respectively for reduction, SGF, break flour, shorts and
bran. AS 2002 Milled fractions revealed higher mean for
fiber and NFE contents while means for all other chemical
constituents were higher in mill streams of Inqulab 91. The
results for chemical composition of milling fractions of
wheat varieties in current are indistinguishable to findings
reported by Saeed et al., (2011) and Akhtar et al., (2005).
Correlation studies: Kernel diameter was significantly
associated with break flour (r=0.99), SGF (r=1.00), milling
score (r=0.96), seed length (r=0.99), SKCS KW (r=0.93)
and protein (r=0.93). SKCS kernel density showed
significant positive relationship with reduction flour
(r=0.87), ash content (r=0.99) and SKCS hardness (r=1.00)
while negative correlation with break flour (r=-0.54), SGF
(r=-0.52) and TKW (r=-0.72) showing that variety with high
kernel density has less break flour yield, more reduction
flour with high ash content. Wheat variety with higher
TKW, seed length and kernel weight whereas less density
and hardness yield more flour as evident from direct
correlation of milling score with TKW (r=1.00), seed length
(r=0.99) and SKCS KW (r=0.99) while inverse relationship
with kernel density (r=-0.73) and SKCS hardness (r=-0.68).
Greater seed length provides assurance for higher flour
recovery. Seed length depicted strong positive association
with break flour (r=1.00), SGF (r=1.00) and TKW (r=0.99)
while kernel density (r=-0.58) and SKCS hardness (r=-0.64)
was negatively related with seed length.
Significant correlation of break flour yield with physical
grain characteristics like TKW (r=0.97), kernel diameter
(r=0.99), milling score (r=0.99), seed length (r=1.00) and
SKCS kernel weight (r=0.92) is indication of higher break
flour yield in wheat variety with soft texture as compared to
hard wheat. Whereas SKCS hardness (r=-0.60) and kernel
density (r=-0.54) were negatively associated with break
flour recovery. SKCS kernel weight exhibited direct
relationship with TKW (r=1.00), break flour (r-0.97), kernel
diameter (r=0.93) and seed length (r=0.98) whereas it was
negatively associated with ash content (r=-o.62), SKCS
hardness (r=-0.78) and kernel density (r=-0.73). Seed length

Varieties in relation to milling quality
140
of wheat grain significant correlation with TKW (r=0.98),
kernel diameter (r=0.99), milling score (r=0.99) while
negatively associated with kernel density (r=-0.58) and
SKCS hardness index (r=-0.64). Wheat variety with greater
TKW, SKCS KW, kernel diameter and seed length yield
more break flour and higher milling score. However, such
wheat variety had less SKCS hardness and kernel density.
PSI and NIR hardness index were highly (r=1.00) associated
while both these parameters showed only weaker
association with SKCS hardness and break flour yield.
Break flour yield and SKCS hardness were inversely related
(r=-0.6) depicting that wheat variety with greater hardness
and PSI value yield less break flour. Hardness index
obtained from SKCS illustrated inverse correlation with
most grain physical like kernel diameter (r=-0.5), SKCS
KW (r=-0.78) and seed length (r=-0.64) and milling
parameters; break flour (r=-0.6) and milling score (r=-0.73).
Protein content showed positive relationship with grain
hardness; NIR hardness (r=0.79), PSI (0.80) and SKCS
hardness (r=0.84). Wheat protein is often positively related
with grain hardness within hard wheats (Giroux et al.,
2000; Slaughter et al., 1992). Hardness was only weakly
associated with absorption (r , 0.3) (Martin et al., 2007).
Grain hardness was negatively correlated with break flour
yield, flour yield, and mixing score and positively correlated
with flour ash (Martin et al., 2007). Hard wheats have
smaller PSI scores than soft wheats due to their larger
particle sizes not passing through the sieve (Edwars, 2010).
SKCS characteristics were significantly correlated with
conventional wheat quality parameters such as kernel size,
wheat protein content, and straight-grade flour yield
(Edwards, 2010). Standard SKCS parameters, seed weight
and diameter measurements made significant correlations
with flour yield (Edwards et al., 2008). SKCS 4100 HI
correlated well with particle size index (PSI) (Osborne et
al., 1997; Williams et al., 1998; Psotka, 1999) and NIR
hardness (Chung et al., 1999).
CONCLUSIONS
Wheat variety AS 02 possessing greater mean score for
physical grain characters like kernel weight, kernel diameter
and seed length and less kernel density and SKCS hardness
index exhibited more break flour, straight grade flour and
milling score but less reduction flour. Linear relationship
between physical grain parameters and break flour yield is
an indication that wheat variety with means for grain
parameters yield higher break flour. Kernel density depicted
positive association with reduction flour and negative with
SKCS hardness and break flour. PSI and NIR hardness were
strongly interrelated but these revealed weak connection
with break flour and SKCS hardness index is a reliable
prediction as less break flour is recovered from wheat
variety with more hardness and PSI values.
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