Packaging materials have a great impact on food quality
2018/8/6 17:51:58
Different types and different structures of packaging materials have different moisture and gas barrier properties, and the cost and use conditions are also significantly different. Therefore, when selecting food packaging materials, comprehensive consideration should be given to the characteristics, quality requirements, expected shelf life, storage and transportation conditions, and cost control of the packaged foods. In general, high-barrier materials are selected as food packaging. In addition to preventing microbial and dust pollution, the most important thing is to isolate the influence of external water vapor, O2 and CO2 on packaged foods, or prevent foods with aroma substances such as tea. The aroma of spices and the like is lost through the packaging.
The penetration of moisture in food packaging can cause physical changes in foods such as dry foods to cause crystallization, agglomeration or loss of brittleness and aroma, as well as some chemical and microbial changes, such as accelerating the oxidative decomposition of oils and pigments. The proliferation of microorganisms and the enhancement of enzyme activity lead to browning of foods. The moisture content has a great influence on the storage quality of fresh foods, grains, dairy products, biscuits, tea, dried fruits and other foods. Therefore, when selecting packaging materials for moisture-sensitive foods, we should first understand the hygroscopic behavior of the foods (determination of isothermal moisture absorption curve and moisture absorption kinetics) and the variation of the quality of the food with the water activity, and then the comprehensive cost and shelf life. Packaging materials having a suitable water vapor transmission rate are selected for storage conditions and the like.
In addition to moisture, the presence of O2 is one of the main causes of the decline in quality of many foods during storage. For example, O2 can cause oil oxidation, produce rancid odor; promote enzymatic browning, cause discoloration of fresh-cut fruits and vegetables; promote the production and reproduction of aerobic microorganisms, cause food rot and deterioration; and certain nutrients in food such as vitamin C, etc. The reaction reduces the quality of the food; if the concentration of O2 is too high or too low, it will affect the respiration intensity of fruits and vegetables after harvest, which will affect its storage time. Materials with good oxygen barrier properties are metal, glass, PVDC, EVOH and high barrier composite films, which can be used together with oxygen absorbers. If the packaged food is sensitive to both water vapor and oxygen, in addition to metal and glass materials for packaging, multilayer composite polymer materials can be selected to achieve both moisture and gas barrier.
With the rapid development of science and technology, various high-barrier materials emerge in an endless stream, especially the flexible packaging materials based on plastics, which provides a guarantee for better extending the shelf life of foods and improving food quality. However, there are also some problems. For example, how to select the most suitable and lowest cost packaging materials according to the characteristics of the packaged foods requires more in-depth and extensive experimental research to provide a more mature and reliable model for industrial applications. At the same time, with the increasing environmental pollution problems, it is necessary to speed up the development of biodegradable polymers with good packaging properties, easy processing and low price to replace the widely used synthetic plastics.