Low Cost Methodology for Package Optimising for Fruit and Vegetables

Abstract

Numerous models are published integrating produce respiration data and gas transmission properties for packaging material in order to predict the optimal equilibrium headspace gas atmosphere. Gaining the data needed for input in the models can be cumbersome, and data found in literature are often given in different units and not stated at the desired storage conditions, e.g., gas transmission rates are usually measured at 23°C. Respiration data might also show great variation due to variety, quality and season, and literature data cannot automatically be transferred to own products. In this work a procedure for measuring produce respiration rates and gas transmission rate of the whole package is outlined. The respiration measurements are performed using low cost equipment and commercial packages as respiration chambers. The obtained results from the measurements for tested products were found to be in accordance with respiration data found in literature. The O 2 and CO 2 transmission rates of the whole packages were measured by a static method using a low cost gas analyser. The method can be used for packages with and without perforations, and it was also possible, within an acceptable accuracy, to calculate the transmission rate for a single hole. The respiration rates were measured at low and abused temperature (2 and 6°C for plums and 5 and 10°C for broccoli). Gas transmission rates of the packages were measured at 5, 10 and 23°C. Finally, a simple predictive model integrating produce respiration rates and gas transmission rate data for the whole package was developed. The modelled data were shown to be in accordance with empirical measurements for plums (Prunus domestica L.) packaged in laser-perforated pouches and for broccoli florets (Brassica oleracea) in sealed trays. The described procedure using low cost equipment and commercial packages is an alternative method for laboratories, packaging material producers, farmers and packaging houses to optimize their packages based on own measurements under realistic storage temperatures. INTRODUCTION Knowledge of produce respiration rates and package transmission rate are two key factors in the choice of appropriate packaging materials for different fruit and vegetables. The choice of product optimised film is crucial to obtain optimum modification of the atmosphere and avoid extremely low levels of O 2 and/or high levels of CO 2 , which could induce anaerobic metabolism with possible off-flavour generation and risk of anaerobic microorganism proliferation (Beaudry, 2000; Watkins, 2000). A lot of effort is further put into modelling of the gas exchange processes continuing inside the package during storage, in order to computerize the selection of the appropriate packaging material without performing huge packaging experiments. The models require a range of different parameters to be defined, with the produce respiration rates and the package transmission rates as the main parameters (Mahajan et al., 2007). Gaining the data needed for input in the models can be cumbersome, and data found in literature are often given in different units and are not stated at the desired storage conditions, e.g., gas transmission rates are usually measured at 23°C. Respiration data might also show great variation due to variety, quality and season, and literature data cannot automatically be transferred to own products.

Full text

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Low Cost Methodology for Package Optimising for Fruit and
Vegetables
H. Larsen
Nofima - Norwegian Institute of Food, Fisheries and Aquaculture Research
Aas
Norway
Keywords: gas transmission rate, packaging, respiration rate, measurements, modelling
Abstract
Numerous models are published integrating produce respiration data and gas
transmission properties for packaging material in order to predict the optimal
equilibrium headspace gas atmosphere. Gaining the data needed for input in the
models can be cumbersome, and data found in literature are often given in different
units and not stated at the desired storage conditions, e.g., gas transmission rates are
usually measured at 23°C. Respiration data might also show great variation due to
variety, quality and season, and literature data cannot automatically be transferred
to own products. In this work a procedure for measuring produce respiration rates
and gas transmission rate of the whole package is outlined. The respiration
measurements are performed using low cost equipment and commercial packages as
respiration chambers. The obtained results from the measurements for tested
products were found to be in accordance with respiration data found in literature.
The O2 and CO2 transmission rates of the whole packages were measured by a static
method using a low cost gas analyser. The method can be used for packages with
and without perforations, and it was also possible, within an acceptable accuracy, to
calculate the transmission rate for a single hole. The respiration rates were
measured at low and abused temperature (2 and 6°C for plums and 5 and 10°C for
broccoli). Gas transmission rates of the packages were measured at 5, 10 and 23°C.
Finally, a simple predictive model integrating produce respiration rates and gas
transmission rate data for the whole package was developed. The modelled data
were shown to be in accordance with empirical measurements for plums (Prunus
domestica L.) packaged in laser-perforated pouches and for broccoli florets (Brassica
oleracea) in sealed trays. The described procedure using low cost equipment and
commercial packages is an alternative method for laboratories, packaging material
producers, farmers and packaging houses to optimize their packages based on own
measurements under realistic storage temperatures.
INTRODUCTION
Knowledge of produce respiration rates and package transmission rate are two key
factors in the choice of appropriate packaging materials for different fruit and vegetables.
The choice of product optimised film is crucial to obtain optimum modification of the
atmosphere and avoid extremely low levels of O2 and/or high levels of CO2, which could
induce anaerobic metabolism with possible off-flavour generation and risk of anaerobic
microorganism proliferation (Beaudry, 2000; Watkins, 2000). A lot of effort is further put
into modelling of the gas exchange processes continuing inside the package during
storage, in order to computerize the selection of the appropriate packaging material
without performing huge packaging experiments. The models require a range of different
parameters to be defined, with the produce respiration rates and the package transmission
rates as the main parameters (Mahajan et al., 2007). Gaining the data needed for input in
the models can be cumbersome, and data found in literature are often given in different
units and are not stated at the desired storage conditions, e.g., gas transmission rates are
usually measured at 23°C. Respiration data might also show great variation due to variety,
quality and season, and literature data cannot automatically be transferred to own
products.
Proc. XIth Int. Controlled and Modified Atmosphere Research Conf.
Eds.: M.L. Amodio and G. Colelli
Acta Hort. 1071, ISHS 2015

328
The aim of this work was to develop a simplified methodology using 1) a low cost
gas analyser and commercial packages as “respiration chambers” in order to measure the
respiration rates for broccoli florets and plums, 2) using the same low cost gas analyser to
measure the gas transmission rates (gas TR) and CO2TR/OTR-ratio (permselectivity,
commonly denoted β) at different temperatures for whole packages with and without
perforations and for the single perforations, and 3) integrate respiration rates and gas
transmission rate data for the whole package into a simplified predictive model using
Microsoft Excel.
MATERIALS AND METHODS
The closed system methodology was used for measurement of the O2 consumption
rates and CO2 production rates (Fonseca et al., 2002; Mahajan and Goswami, 2001).
Large pieces of 100-g broccoli florets (two replicates at 5 and 10°C) or 500 g plums
(three replicates of each plum cultivar at 2 and 6°C) were placed into a commercially
available package (“respiration chamber”). The package consisted of a 1500-ml high
density polyethylene (HDPE) tray from Promens (Kristiansand, Norway) top sealed with
a barrier film from Wipak (Nastola, Finland) with ethylene vinyl alcohol (EVOH) as the
barrier layer. The top film was sealed on the trays using a Polimoon 511VG tray sealing
machine from Promens (Kristiansand, Norway). The starting atmosphere in the headspace
of the packages was air. Just after packaging, the sealed packages with product were
placed into two Termaks chill cabinets (Bergen, Norway) at the desired temperatures. The
O2-and CO2-concentrations in the headspace of the packages were recorded at relatively
constant intervals within the next 13 h using a CheckMateII O2/CO2-analyser from PBI-
Dansensor (Ringsted, Denmark). The gas samples were withdrawn by the help of a needle
connected to the gas analyser, through a septum placed on the lid. The oxygen
consumption rate (RO2) and carbon dioxide production rate (RCO2) were calculated using
linear regression similar to the procedure outlined by (Fonseca et al., 2002; Iqbal et al.,
2005). Oxygen transmission rate (OTR) and carbon dioxide transmission rate (CO2TR) in
the packages were measured using a modification of the Ambient Oxygen Ingress Rate
(AOIR) method (Larsen et al., 2000). The AOIR method measures the OTR of whole
packages using a low cost gas analyser. A later work (Larsen and Liland, 2013)
demonstrates the determination of both O2 and CO2-transmission rates and
permselectivity at different temperatures for whole perforated and non-perforated
packages and the single perforations. 1100- and 1500-ml HDPE trays were flushed with
the gas mixture 5% O2, 10% CO2 and 85% N2 before sealing with three different top webs
using the same tray sealing machine as described above. Another series with 1758±99 ml
pouches made from 25 µm biaxially oriented polypropylene (BOPP) film were flushed
with the same gas as above using a tube. The flushed packages were stored in climate
chambers for 5-7 days at different temperatures. Changes in headspace gas composition in
the packages during time were recorded several times using a CheckMateII O2/CO2-
analyser (PBI Dansensor, Ringsted, Denmark).
The data from the respiration and transmission rate analyses were finally
integrated into a predictive simplified model using Microsoft Excel, originally developed
by Schlemmer and Allermann (2008).
RESULTS AND DISCUSSION
The O2 and CO2 concentration in the packages and the calculated respiration rates
for the broccoli florets measured at 5 and 10°C and the plums (‘Victoria’ and ‘Reeves’)
measured at 2 and 6°C are presented in Figures 1 and 2. The measured respiration rates
are at the same level as values found in the produce fact sheet presented at the homepage
for the Postharvest Technology Centre at the University of California (Cantwell and
Suslow, 1997; Mitcham et al., 1996), although the P. domestica plums seem to have
slightly higher respiration rates than P. salicina plums.
A few selected results showing gas transmission rates in different packages are

329
presented in Figures 3-5. Figure 3 shows the increasing gas TR for the packages as the
number of perforations increases. Figures 4 and 5 demonstrate the difference in
permselectivity and temperature influence between perforated and non-perforated
materials. The permselectivity for the perforated materials in our study (Larsen and
Liland, 2013) was in the range 0.9 to 1.0 for whole packages, and 0.8 to 0.9 for the single
perforations (Fig. 4), which is in accordance with the findings of other authors (Fonseca
et al., 2000; Gonzalez et al., 2008). No significant difference was found between average
values for OTR and CO2TR for the single perforations in packages stored at 5, 10 and
23°C, whereas gas TR for the HDPE-tray with non-perforated OPP/PE film increased by
a factor of 2.4 by storage at 23°C compared to 5°C (Fig. 5).
The results comparing the predicted gas concentration in the packages to the
measured values in packages with broccoli and plums are presented in Figures 6 and 7,
respectively. The predicted O2 and CO2 curves are close to the exact O2 and CO2
concentrations measured in the packages, and especially the curves for the ‘Victoria’
plums show a good fit. For the broccoli, the predicted O2-curve is slightly lower, and the
predicted CO2-curve slightly higher than the exact values. This phenomenon can probably
be explained by the use of a constant O2 consumption and CO2 production rate, which
may be inaccurate as the O2 concentration approaches approximately 4-5%. A low O2/
high CO2 concentration will usually reduce the respiration rates, depending on type of
produce, and an enzymatic kinetic mechanism (Michaelis-Menten type) is often used to
describe respiration (Fonseca et al., 2002). However, in most practical cases for the
greater part of fruit and vegetables, the optimised O2 concentration in the package will be
above 10% O2, and a constant respiration rate is sufficient for simplified modelling. For
plums, in particular, the maximum tolerance CO2 concentration is 5% or lower (Larsen
and Vangdal, 2013).
CONCLUSION
A commercial package was used as “respiration chamber” in order to measure
respiration rates for broccoli florets and plums. The gas transmission rates for whole
perforated and non-perforated packages and for the single perforations were measured for
different types of packages. A low cost gas analyser was used for measurement of the
changes in gas concentration during time inside both the “respiration chamber” and the
empty, whole packages flushed with gas. The measured respiration rates and the gas
transmission rates for the single perforations using this low cost equipment were found to
be in accordance with and at the same levels as found by other researches, confirming a
sufficient accuracy of the used techniques. The respiration rates and gas transmission
rates for the packages and single perforations were integrated into a simplified predictive
model using Microsoft Excel. The modelled data showed acceptable fit to exact data
measured in packages with broccoli florets and plums stored for 120 h and 30 days,
respectively.
ACKNOWLEDGEMENTS
Thanks to Aud Espedal for valuable help running the packaging machine and
preparation of packages for gas measurements and Kristian Hovde Liland for support and
as co-author during the development of the gas transmission rate method and the
prediction model used in this work. Agricultural Food Research Foundation (Oslo,
Norway) is greatly appreciated funding this project.
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331
Figures
Fig. 1. O
2
(1a) and
CO
2
(1b) measurements in packages with broccoli at 5 and 10°C
(mean of two replications) and calculated O
2
consumption rates (O
2
CR) and CO
2
production rates (CO
2
PR) for broccoli (1c).

332
Fig. 2. O
2
(2a) and CO
2
(2b) measurements in packages with plums (‘Reeves’ and
‘Victoria’ at 2 and 6°C, mean of 3 replications) and calculated O
2
consumption
rates (O
2
CR) and CO
2
production rates (CO
2
PR) for plums (2c).
Fig. 3. O
2
and CO
2
transmission rates for packages (Micro-PET = HDPE-tray + PET/PE
top web) with 0, 1, 2, 3 and 4 perforations.

333
Fig. 4. O
2
and CO
2
transmission rates for single perforations measured at 5, 10 and 23°C.
Fig. 5. O
2
and CO
2
transmission rates for non-perforated packages (HDPE-trays +
OPP/PE top web) measured at 5 and 23°C.

334
Fig. 6. Predicted and measured O
2
and CO
2
concentrations in packages with 3
perforations with 100 g broccoli and stored at 10°C for 120 h.
Fig. 7. Predicted and measured O
2
and CO
2
concentrations in packages with 11
perforations with 750 g ‘Victoria’ plums and stored at 2°C for 30 days.