1. Moisture absorption of vacuum fried food
Crispy feeling is the characteristic of vacuum fried food. To keep the crispness of fried food, its moisture content should be controlled within 5%, so the problem of moisture absorption (moistureproof) during storage should be seriously considered. The strong hygroscopicity of vacuum fried food is mainly due to its puffing and porous product structure, so it has strong hygroscopicity. Different vacuum fried foods have different hygroscopicity. Vacuum fried food of agricultural products has stronger hygroscopicity than vacuum fried food of meat and aquatic products.
In short, vacuum fried food should be packed with nitrogen and water to keep it crisp and ensure a long shelf life. According to the different types of packaging, packaging can choose the purity of nitrogen filling, and directly vacuum nitrogen filling, so as to create an anoxic microenvironment for the packaged goods, maintain their activity, inhibit their breathing and mold growth, keep the stored goods dry, and prevent them from becoming moldy due to moisture.
2. Oxidation of oil during storage
Vacuum fried food has a porous structure, and a layer of oil is adsorbed on the surface of the pores, which cannot be removed by centrifugal degreasing, so vacuum fried food has a certain oil content. In the storage process of products, if oil comes into contact with oxygen, the oxidation reaction of oil will occur, and the degree of oxidation of oil is measured by the price of hydrogen peroxide.
The Food Hygiene Law has strict regulations on the peroxide price of products, and products cannot exceed these standards when they reach consumers. Light, oxygen and temperature are the promoting factors of oil oxidation, that is, peroxide value. The influence of these main factors is discussed below.
(1) storage temperature
The oxidation rate of oils and fats is significantly accelerated with the increase of temperature, and the oxidation rate is as high as twice that of 10℃. When vacuum fried food is packed with nitrogen, the effect of temperature on the shelf life of food will be significantly reduced. The product is stored at room temperature for 12 months, but stored at 50℃ for 2 months, the peroxide value of the product will exceed the standard.
(2) the concentration of oxidation
The experimental results of the influence of oxygen concentration on peroxide value in Japanese vacuum fried food show that the higher the oxygen concentration, the faster the oxidation reaction and the faster the peroxide value rise. To make the shelf life of the product reach half a year, the oxygen concentration should be lower than 2%; In order to make the product shelf life reach one year, the oxidation concentration should be lower than 65438 0%.
Source: China Food Information Network