Model and Simulation of modified atmosphere packag

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Model and Simulation of modified atmosphere packaging for fruits and vegetables (Part 1)

[Abstract] this paper mainly discusses the principle of modified atmosphere packaging system and establishes a dynamic change model of internal environment. On this basis, many parameters affecting the packaging environment were classified, and the changes of three gas concentrations in the packaging environment with time were simulated by computer simulation technology

[Key words] modified atmosphere packaging; Model; Simulation

1 Introduction

after the product is placed in the packaging container and sealed, a certain internal packaging environment is formed between its outer surface and the packaging materials. Internal environment atmosphere is a direct factor affecting product quality. It is one of the effective means to extend the shelf life of products by using certain technologies to control the internal environment of packaging. The commonly used methods include vacuum packaging, decompression packaging, modified atmosphere packaging and deoxygenation packaging. For fruits and vegetables, which still have life activity during the storage period after picking, and perform respiration and transpiration, modified atmosphere packaging is an effective packaging technology, which must comprehensively consider energy efficiency, environmental protection and product quality

according to the control degree of the environmental atmosphere inside the package after packaging, modified atmosphere packaging can be divided into controlled atmosphere packaging (CAP) and modified atmosphere packaging (map). However, no matter which company starts to fully implement the good practices and experiences of work areas 3 and 6, the gas components in the packaging environment are different from the normal atmospheric environment. The most common changes are the decrease of oxygen concentration and the increase of carbon dioxide concentration

2. Quality assurance mechanism of modified atmosphere packaging

the commonly used filling gases for modified atmosphere packaging mainly include oxygen, carbon dioxide, nitrogen and their mixtures, and other rarely used gases include nitrogen dioxide, sulfur dioxide, argon, etc

oxygen is an essential filling gas for modified atmosphere packaging of fresh fruits and vegetables, because the fruits and vegetables will be breathed after harvest (consuming oxygen, discharging ester gases such as carbon dioxide and ethylene). If there is no oxygen, anaerobic respiration will be carried out, which will accelerate the change of sensory quality and decay. Oxygen can also inhibit the growth of anaerobic bacteria

carbon dioxide is a key gas in modified atmosphere packaging. It can inhibit the growth of bacteria and fungi. When used in fruit and vegetable packaging, it can strengthen oxygen reduction and reduce respiratory intensity. However, when using carbon dioxide, it must be noted that the solubility of carbon dioxide in water is very high, and the formation of carbonic acid after dissolution will change the pH value and taste of fruits and vegetables. At the same time, after carbon dioxide dissolves, the gas in the package will be reduced, which will easily lead to shrinkage and unsatisfying of the package and affect the appearance. The use of carbon dioxide in modified atmosphere packaging must consider many factors, such as storage temperature, water content of fruits and vegetables, species and quantity of microorganisms

as an ideal inert gas, nitrogen generally does not have chemical interaction with food. If the nitrogen concentration is increased in the packaging, such as equipment operation status, program control operation steps, whether the extension meter is switched, etc., the oxygen concentration is relatively reduced, which can inhibit bacterial growth and prevent food oxidation. Nitrogen does not directly interact with microorganisms in food. It plays two roles in modified atmosphere packaging: one is to replace and inhibit the respiration of food itself and microorganisms; Second, as a filling gas, it ensures that the product still has a good shape in the package

the ratios of the above three gases required by different fruits and vegetables to maintain their normal metabolism and keep them fresh are different, which depends on the variety of fruits and vegetables and will not produce many factors such as complications and maturity like other materials

p and the principle of cap air conditioning system

map refers to the one-time replacement of ideal gas or the establishment of predetermined regulated gas concentration in the air conditioning system, which will not be subject to artificial adjustment during subsequent storage

cap refers to the control of all gas environment around the product, that is, during controlled atmosphere storage, the concentration of the selected regulated gas has been managed or controlled stably

for food with physiological activity, reducing oxygen concentration and increasing carbon dioxide concentration can inhibit and reduce aerobic respiration of fresh food, reduce water loss, and inhibit microbial reproduction and enzyme reaction. However, if there is excessive hypoxia, it will be difficult to maintain the metabolism necessary for life, or cause anaerobic respiration, taste change or adverse physiological reactions and deterioration. Cap or map is not simply to remove oxygen, but to improve and control the atmosphere and environment of food storage, so as to significantly extend the validity of food packaging. To judge whether an air conditioning system is cap type or map type, the key is to see whether it has the function of adjusting and controlling the established internal environment atmosphere

the model of the film modified atmosphere packaging system for fruit and vegetable products can be described in Figure 1. There are two processes in this system: one is the physiological and biochemical process of products (including microorganisms), that is, the respiratory process of metabolism; Second, the permeability of the film leads to the exchange process between the product and the gas in the package. These two processes make the film air conditioning system a dynamic system, which can achieve dynamic balance under certain conditions, that is, the exchange rate between the product and the ambient gas in the package is equal to the exchange rate between the ambient gas in the package and the atmosphere through the film

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