Development of user-friendly software for design of modified atmosphere packaging for fresh and fresh-cut produce

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Abstract

There is a wealth of published information on modified atmosphere packaging (MAP) but a lack of systematic treatment of the data in order to develop knowledge management systems that can provide information to users on which films to use for particular purposes and targets. This paper reports the development of user-friendly software for MAP design of fresh and fresh-cut produce. The software can select suitable packaging materials and define the amount of product to be packed or the area of the film that should be available for gas exchange. Two databases have been built in the software, which include recommended gas composition for 38 products, 75 respiration rate models, and permeability data for 27 polymeric films. This software was successfully tested for some products and an example for mango and Galega kale is described.

Industrial relevance

The PACKinMAP software selects the best possible film type for the given type of fresh or fresh cut fruit/vegetable. A manufacturer can type in a specific food product, such as a golden delicious apple, and the software will tell him the ideal type of packaging material according to the supplier or the retailer's needs. The software has also been found to simulate the package for any type of real-life distribution temperature history thus testing the ability of the package to withstand abuse.

Introduction

Modified atmosphere packaging (MAP) of fresh produce relies on modification of the atmosphere inside the package, achieved by the natural interplay between two processes, the respiration of the product and the transfer of gases through the packaging, that leads to an atmosphere richer in CO2 and poorer in O2. This atmosphere can potentially reduce respiration rate, ethylene sensitivity and production, decay and physiological changes, namely, oxidation (Kader et al., 1989, Saltveit, 1993).

The objective of MAP design is to define conditions that will create the atmosphere best suited for the extended storage of a given produce while minimising the time required to achieve this atmosphere. This can be done by matching the film permeation rate for O2 and CO2 with the respiration rate of the packaged produce. As different products vary in their behaviour and as MA-packages will be exposed to a dynamic environment, each package has to be optimised for specific demands (Chau and Talasila, 1994, Jacxsens et al., 2000, Saltveit, 1993). A MAP system not properly designed may be ineffective or even shorten the storage life of a product: if the desired atmosphere is not established rapidly the package has no benefit; if O2 and/or CO2 levels are not within the recommended range, the product may experience serious alterations and its storage life is shortened.

Exama, Arul, Lencki, Lee, and Toupin (1993) calculated the required O2 and CO2 permeability for various fruits and vegetables to create optimal gas concentrations in the MA packages. These calculations were based on the steady state respiration rate whereas in MA package the respiration rate changes as the atmosphere is modified. Hence, the design should take into consideration not only steady-state conditions (product respiration rate and film permeability), but also the dynamic process, because if the product is exposed for a long time to unsuitable gas composition before reaching the adequate atmosphere, the package may have no benefit. Storage temperature is never constant in the distribution chain of fresh produce. Due to the temperature dependence of the respiration rate and of the gas permeability of a packaging film, fluctuating temperatures result in changes of the internal O2 and CO2 concentrations (Jacxsens et al., 2000). Because of the difference in the rates of change of permeability and respiration rate with temperature, a film that produces a favourable atmosphere at the optimal storage temperature may cause excessive accumulation of CO2 and/or depletion of O2 at higher temperatures, a situation that could lead to metabolic disorders (Beaudry et al., 1992, Cameron et al., 1994, Cameron et al., 1993, Exama et al., 1993, Joles et al., 1994). A package poorly designed may actually reduce the product shelf life and even induce anaerobiosis, with the possible growth of pathogens and concomitant effects on product safety.

There is a wealth of published information on MAP, yet no systematic theoretical study has been conducted to establish which commercially available plastic films would be most suitable for MAP of a particular produce (Exama et al., 1993). Such analysis could provide an initial screening of polymeric films, point out potential limitations, and help minimise the number of experimental trials. Simulation of a MAP system is the most appropriate method to allow a correct MAP design and consequently obtain a successful commercial product. The “pack and pray” procedure may have economic and safety hazard consequences and the “trial and error” approach is an extremely time consuming procedure. The objective of the work reported in this paper was to develop and test user-friendly software, called PACKinMAP, for designing MAP for fresh and fresh-cut respiring products.

Section snippets

Design methodology

MAP design requires the determination of intrinsic properties of the produce, i.e. respiration rate, optimum O2 and CO2 gas concentrations, and film permeability characteristics. The ultimate aim of this design process is to select suitable films for a given product, its area and thickness, filling weight, equilibrium time, and the equilibrium gas composition at isothermal and non-isothermal conditions.

When several films can be used to provide a protective atmosphere, their cost will be a major

User interface

The user interface of the software was built in Matlab Guide version 6.5.1 (MathWorks, Inc. Natick, US). It contains two main menus: Commodity and Package. The commodity menu shows the list of fruits and vegetables available and their optimum conditions. It also gives an input dialogue box for entering the temperature profile during the distribution chain. The package menu shows the predefined geometries, polymeric films database and perforation based packaging system.

Case study

A case study is presented to illustrate the use of the software (termed PACKinMAP) to design a modified atmosphere package for 1 kg of whole mango var. Nam dok mai (Charoenchaitawornchit, Kanlayanarat, & Tongta, 2003) packed in a 1.792 × 10 3 m3 tray at 10 °C. For the selected commodity and at given optimum conditions, βmin and βmax were found to be 1.71 and 3.84, respectively. Based on this β range, there are 11 films selected out of the 27 included in the database (see Table 3). Ethyl cellulose

Conclusions

A software can be developed and used as a tool to speedily analyse the adequacy of various packaging systems to generate a proper equilibrium modified atmosphere for each packaged fresh whole/fresh cut product. To reach this optimal atmosphere inside the package, the software developed in this work (PACKinMAP) simulates O2 and CO2 concentrations for different combinations of films, area, and weight, avoiding time-consuming experiments to determine the best film to be used in packaging each type

Acknowledgement

The authors acknowledge financial support from the Irish Government, under the National Development Plan 2000–2006, in the framework of the Food Institutional Research Measure managed by the Department of Agriculture, Food and Rural Development.

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