Modified atmosphere packaging (MAP) of fresh produce relies on the modification of atmosphere inside the package achieved by the natural interplay between two processes: the respiration rates of the commodity and the permeability of the packaging films. MAP has been a proven technology to meet the consumer's demand for more natural and fresh foods, which is increasing day by day. Because of its dynamic phenomenon, respiration and permeation take place simultaneously, and it is necessary to design the MAP system and select the matching films to achieve desired atmosphere early and maintain as long as possible. To meet the desired film characteristics for MAP, the different plastic films are either laminated or coextruded. In this modern world, the packaging films of required gas transmission properties are made available through advanced technology. Although the MAP industry has an increasing choice of packaging films, most packs are still constructed from four basic sustainable polymers: polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyproylene (PP) and polyethylene (PE) for packaging of fresh produce. Polystyrene has also been used but polyvinylidene, polyester and nylon have such low gas permeabilities that they would be suitable only for commodities with very low respiration rates.

No abstract

No abstract

Modified atmosphere packaging (MAP) is a dynamic system during which respiration and permeation occur simultaneously. Hence factors affecting both respiration and permeation were considered for designing a package. In the design of MA packages for guava (cv. Baruipur) a total of 13 variables were considered. The independent variables includes: weight of fruits, surface area of packaging film, free volume of the package, thickness of the film and permeabilities of film to O 2 and CO 2 gas. The fixed variables considered were: the surrounding gas composition and temperature, the respiration rates for O 2 consumption and CO 2 evolution, and the equilibrium gas compositions to be attained in the package so that the fruit's shelf-life is extended. Two types of MA packages, having package size of 19 cm× 19 cm for a fill weight of 1,000±100 g were developed. Packages were designed to accommodate a fill weight range of 0.90-1.10 kg. Various package parameters were optimized to facilitate establishment of dynamic equilibrium at target levels of O 2 and CO 2 concentration in the package. The storage study of MA packages was performed at 10, 15, 20 and 25°C temperatures. The performance of film packages was evaluated for their ability to establish equilibrium at target levels and to extend the shelf life of the packaged fruit. The MA packaging system increased the shelf life of guava by 128-200 % compared to the unpacked fruits at various storage temperatures with a quality comparable with the freshly harvested commodity.

MAP is a dynamic system where respiration of the packaged product and gas permeation through the packaging film takes place simultaneously. The desired level of O 2 and CO 2 in a package is achieved by matching film permeation rates for O 2 and CO 2 with respiration rate of the packaged product. A mathematical model for MAP of fresh fruits applying enzyme kinetics based respiration equation coupled with the Arrhenious type model was developed. The model was solved numerically using MATLAB programme. The model was used to determine the time to reach to the equilibrium concentration inside the MA package and the level of O 2 and CO 2 concentration at equilibrium state. The developed model for prediction of equilibrium O 2 and CO 2 concentration was validated using experimental data for MA packaging of apple, guava and litchi.

Several experiments were conducted at different storage temperatures for generating respiration data using close system method for respiration. A respiration rate model, based on enzyme kinetics and the Arrhenius equation was proposed for predicting the respiration rates of Guava as a function of O 2 and CO 2 concentrations and storage temperature. Temperature was found to influence the model parameters. In this model, the dependence of respiration rate on O 2 and CO 2 was found to follow the uncompetitive inhibition. The enzyme kinetic model parameters, calculated from the respiration rate at different O 2 and CO 2 concentration were used to fit the Arrhenius equation against different storage temperature. The activation energy and respiration pre-exponential factor were used to predict the model parameters of enzyme kinetics at any storage temperature between 0-30 • C. The developed models were tested for its validity at 12 • C and it was found to be in good agreement (the mean relative deviation moduli between the predicted and experimental respiration rates were found to be 8.95% and 8.02% for O 2 consumption and CO 2 evolution, respectively) with the experimentally estimated respiration rates.

Respiration of the produce and permeation of gas through the packaging films are the processes involved in creating a modified atmosphere inside a package that will extend shelf life of agricultural perishables. Thus modeling respiration rate of the selected produce is crucial to the design of a successful modified atmosphere packaging system. Two different models based on regression analysis and enzyme kinetics were developed with the help of respiration data generated at temperatures 0, 5, 10, 15, 20, 25, and 30°C for litchi fruit using the closed system method. Temperature was found to influence the model parameters. In the model, based on enzyme kinetics, the dependence of respiration rate on O 2 and CO 2 was found to follow the uncompetitive inhibition. The enzyme kinetic model parameters, calculated from the respiration rate at different O 2 and CO 2 concentration were used to fit the Arrhenius equation against different storage temperature. The regression coefficients values were used for the prediction of respiration rate using regression model. The activation energy and respiration pre-exponential factor were used to predict the model parameters of enzyme kinetics at any storage temperature. The developed models were tested for its validity at 2°C. The models showed good agreement with the experimentally estimated respiration rate. Nomenclature a Regression coefficient b Regression coefficient, h E Mean relative deviation modulus, % E a Activation energy, kJ g −1 mol −1 k m(O2) Michaelis-Menten constant for O 2 consumption, % O 2 k m(CO2) Michaelis-Menten constant for CO 2 evolution, % O 2 k i(O2) Inhibition constants for O 2 consumption, % CO 2 k i(CO2) Inhibition constants for CO 2 evolution, % CO 2 N Number of respiration data points R Universal gas constant, 8.314 kJ kg −1 mol −1 K −1 R CO2 Respiration rate, ml [CO 2 ] kg −1 h −1 R exp Experimental respiration rate, ml kg −1 h −1 R m Model parameter of enzyme kinetic R pre Predicted respiration rate, ml kg −1 h −1 R O2 Respiration rate, ml [O 2 ] kg −1 h −1 R p Respiration pre-exponential factor T Storage temperature°C T abs Storage temperature, K t Storage time, h Δt Time difference between two gas measurements V f Free volume of the respiration chamber, ml v m(CO2)

Optimization of machine parameters using response surface methodology (RSM) greatly overcomes the numbers of experimental trials generally undertaken for milling study of pigeon pea apart from maximizing the output of the system. The independent milling parameters for Central Institute of Agricultural Engineering dal mill viz., roller speed, emery grit size, and feed rates were optimized for pigeon pea dehulling using RSM. The roller peripheral speed of 9.6 m/s, emery grit size 1 mm, and feed rate 111 kg/h were found optimal. The dal recovery and milling efficiency at optimized independent parameters were 75% and 80%, respectively.