Which of the Following is A Sign of Food Spoilage

Eating spoiled food is very harmful to the human body. We often do not know whether some food is spoiled. In fact, spoiled food will “express” to you. What are the characteristics of spoiled food? Let’s take a look at how spoiled food “expresses” to you.

Sign of Food Spoilage

What are the signs of Food Spoilage?

Yogurt turns too sour

The acidity of yogurt is limited. If the yogurt is out of the cold chain during storage and logistics, such as being left at room temperature or in an outdoor environment, the lactic acid bacteria will multiply rapidly and the acidity of the yogurt will increase, which is beyond the acceptable range. Such yogurt The taste will be very sour, and the activity of lactic acid bacteria will decrease, and the degree of denaturation of milk protein will increase, which is not conducive to human absorption and gastrointestinal health. The longer it is stored, the harder it is to guarantee the quality of yogurt. Therefore, do not buy a lot of yogurt at one time, try to buy it now and drink it now.

Potatoes turn brown after being cut and freshly squeezed juice changes color

“Phenol oxidase” is naturally present in fruits, vegetables and potato foods, and is also rich in “polyphenols” with antioxidant effects. If they meet together and add oxygen, “enzymatic browning” will occur. , that is, phenol oxidase catalyzes the oxidation of colorless polyphenols to generate colored “quinones”. These quinones can polymerize with each other, making the color darker and darker. Although no harmful substances are produced in this process, the antioxidant capacity of polyphenols decreases after browning, and it is also accompanied by the loss of vitamin C. To avoid this reaction, scald the raw materials with boiling water before juicing to inactivate the phenol oxidase, or add a piece of vitamin C when juicing in vinegar water.

Roasted meat produces reddish brown, roasted buns turn yellow

When food containing carbohydrates and amino acids is cooked at a high temperature above 120 °C, the color will turn yellow and brown, and at the same time, an attractive aroma will be released. This reaction is called the Maillard reaction. Such as braised meat, roast duck, toast, pancakes, frying… All kinds of treatments that turn dark brown after cooking, almost all promote the Maillard reaction. Acrylamide (a carcinogen) is a by-product of this reaction. It has nothing to do with aroma itself and has no color, but in general, the darker the color and the stronger the aroma after the food is heated, the higher the acrylamide content. . Therefore, do not bake steamed bread and bread slices to the point of being too yellow, and try to eat less baked, fried, and puffed potato products, such as fried potato chips, etc.

Boiled purple cabbage turns blue

Foods such as strawberries, purple cabbage, purple potatoes, and purple rice are rich in anthocyanins, which are powerful antioxidants that protect the body from free radical damage. The characteristic of anthocyanin is that it is red in acidity, and usually turns blue in alkalinity, and there may be transitional colors such as purple and green in the middle, while the water in the north is generally weakly alkaline. These discolorations are normal and can be eaten with confidence, but generally speaking, anthocyanins are relatively stable under acidic conditions. For example, if you add a little vinegar, the color of purple cabbage will be more red and bright.

Leafy greens turn yellow after frying

The reason why green vegetables appear green is mostly due to magnesium ions in chlorophyll. When light shines on chlorophyll, porphyrins containing magnesium ions (a compound in chlorophyll) will make other colors of light come and go, only letting the light come back and forth. Green light is reflected back. But during heating, chlorophyll is very unstable. Studies have shown that the acetic acid (acetic acid) in vinegar will destroy the structure of chlorophyll, turning chlorophyll into “pheophytin”, and the vegetable will quickly turn yellowish brown. Therefore, stir-fry green leafy vegetables with less or no vinegar.

Floccules appear when the milk is heated

There are two reasons for the flocculent formation of milk after heating. First, certain proteases present in milk alter the structure of the proteins in the milk, thereby destabilizing the milk, resulting in denaturation and coagulation during heating. Although such milk has not expired, it is not recommended to drink. Second, the proliferation of microorganisms remaining in the milk leads to changes in the acidity of the milk, which further destabilizes the milk, resulting in the appearance of floccules. In short, it is not recommended to drink milk with floccules after heating.

White Hair in Vinegar

The “white hairs” growing in vinegar are likely to be the floating film of mold flowers produced by Mucor, which is widespread in the environment. If the vinegar white hair is simply caused by Mucor, it will not be a big problem to remove the mold and continue to eat. However, there are other pathogenic bacteria in the air. If they also multiply in vinegar, it may bring health threats. Therefore, it is best not to continue to eat vinegar with white hair.

Do you know which is A Sign of Food Spoilage now?

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