Any food will go bad after being left at room temperature for a period of time. Some are moldy and caked, some are rotten and smelly, and some are sour.
There are three main reasons for food deterioration:
1, microorganism. There are microorganisms everywhere in the environment, and food is easily contaminated by microorganisms in the process of production, processing, transportation, storage and sales. As long as the temperature is appropriate, microorganisms will grow and reproduce, decompose nutrients in food and meet their own needs. At this time, the protein in food will be destroyed, the food will become smelly and sour, lose its original toughness and elasticity, and the color will also change.
2, the role of enzymes. There are many kinds of enzymes in animal food. Under the action of enzymes, the nutrients in food are broken down into a variety of low-grade products. Usually rice turns sour and fruit rots, that is, carbohydrates are decomposed and fermented by enzymes.
3. Chemical reaction of food. Oils and fats are easily oxidized, resulting in a series of chemical reactions. Oil has a strange smell after oxidation, such as fat turning from white to yellow.
Deteriorated food not only changes in appearance, but also loses the color, fragrance and taste quality of the original food, and its nutritional value will also decrease, and it will also contain corresponding toxins harmful to human health. [2]
Somatotype identification
Food corruption is a complex biochemical reaction process, involving the role of enzymes in food, the growth and metabolism of polluting microorganisms, but mainly the role of ex-factory microorganisms. Judging from the influence of corruption on food sensory quality, food corruption mainly has the following types.
1. viscosity: the viscosity of spoiled food is mainly caused by polysaccharides formed by bacterial growth and metabolism, which often appears in foods mainly containing carbohydrates. The common microorganisms that change food education are Alcaligenes colloid, Alcaligenes quasi-Alcaligenes, Achromobacter, Aerobacillus, Lactobacillus, Leuconostoc and so on. Some yeasts can also make food rotten and sticky.
2. Acidification: Food souring usually occurs in carbohydrate foods and dairy products. The sour taste of food is mainly caused by the growth and metabolism of spoilage microorganisms, which mainly include acetic acid, propionic acid, Pseudomonas, micrococcus, streptococcus lactis and lactic acid bacteria. A few molds, such as Rhizopus, will also use carbohydrates to produce drums, which will cause food spoilage.
3. Odor: The smell of food is mainly caused by organic amine, ammonia, sulfur poisoning and feces produced by bacteria decomposing protein foods. Common bacteria that decompose protein are Fusobacterium, Proteus, Bacillus and so on. [3]