Research On The Theory Of Modified Atmosphere Packaging With Performated Film And Its Application In High Respiration Rate Of Fruit And Vegetable Packaging

Modified atmosphere packaging(MAP)is the most effective way for keeping fruit and vegetable freshness in the domestic and international, which according to different physiological characteristics of fruit and vegetable products, natural gas or two or three kinds of gas mixed was used to replace the gas in package, by choosing permeability of film to regulate. However, common packaging film in market, the permeability is very small, especially for the high respiration rate of fruits and vegetables; very few can meet the requirements of high respiration rate of fruit and vegetable in modified atmosphere package. Then different specifications of holes or perforations were made in film to improve the solution. Perforated film was more effectively to regulate the gas exchange inside and outside packaging bags, to reduce the risk arising from anaerobic environment, to extend the shelf life of fruits and vegetables. Therefore, the design of suitable perforated film technology has become one of the studies the fruit and vegetable preservation currently.In this paper, the gas transfer theory and applications of perforated film were extensive researched, the Lentinula eddoes and Spinaches. of high respiration rate were made as the research object, the theory of modified atmosphere packaging with perforated film and its application in fruits and vegetables of the high respiration rate were systematic studied, the specific content can be divided into five components:1) The mathematical model of gas exchange in modified atmosphere packaging with perforated film was established and verified. The diffusion mechanism of gas through the perforated film was theoretical analyzed, respectively, based on the Knudsen proliferation, the spread of the transition; Fick diffusion and the Stephan-Maxwell, the mathematical model of the gas exchange in modified atmosphere package with perforated film were developed. The experiments that no products in modified atmosphere package of pre-sealed atmosphere with the perforated film with different specifications were carried out based on Fick diffusion theory mathematical models, and on this basis of perforation parameters (size, number and length) of the impact of gas exchange was analyzed. The results showed that the mathematical model predicted values has good agreement with the experimentally estimated gas concentration, the impact of perforation size and number were notable, and length is not significant.2) The respiration rate of Lentinula eddoes and Spinaches were measured and characterized. Use the close method to measure the respiration rate of Lentinula eddoes and Spinaches, apply the enzymes - power (Enzyme-kinetic) model, and select the Michaelis-Menten equation to characterize. And model value was compared with test measurements value.3) The mathematical model of gas exchange in modified atmosphere packaging of fruits and vegetables with perforated film was established and verified. Based on the Fick's law, combined with fruit and vegetable respiration rate model, a mathematical model in MAP with perforated film was developed. The testing system of the gas composition and perforation number in modified atmosphere packages was established. Fresh Lentinula eddoes were packaged in different initial gas composition and perforation number, and the model prediction and experimental values was compared. In general, the model predictions agree well with the experimental data.4) The design of modified atmosphere packaging with perforated film is crucial to ensuring the quality of fruits and vegetables. Based on the Fick theory and respiratory evaporation model, combined with fruit and vegetable respiration rate model, considering the fruits and vegetables that were packaged, atmosphere, temperature and humidity and other factors, according to the mass and energy conservation law, the mass and energy balance model was established in modified atmosphere packaging with perforated film. On this basis, the total area of perforations equation in modified atmosphere packaging of fruits and vegetables was derived. And the parameters of perforations in modified atmosphere package of fruits and vegetables were determined.5) The application of MAP with perforated film. The Spinaches of high respiration was the study object, according to the fourth part of program design the suitable perforations parameter (2-hole, 262.7-micron aperture; 3-hole 214.5-micron diameter), the Spinaches was packaged with this perforated film the non-perforated sealed packaging was the comparison group. The gas concentration of O2, appearance, weight loss, color difference and chlorophyll content of Spinaches in the modified atmosphere packages were assayed. And the effects of modified atmosphere package with perforated film for storing Spinaches were evaluated, and non-perforated sealed packaging for comparison. The results showed that while the packages with perforated film at 5℃in the5%~7%O2+9%~12%CO2 for storing Spinaches, the maintenance of good in the form of spinach, lower respiratory rate was ensured by set 2 perforations on the film.