It is easy to lead to unsuccessful flour fermentation, so yeast can't be used after it expires. Moreover, yeast will deteriorate after expiration and produce some harmful substances. If you continue to use it, it will be mixed with food, leading to food poisoning or gastrointestinal discomfort, so no matter what food expires, you can't use it again.
Extended data:
The influence of corrupt food villages on human health is mainly manifested in the following three aspects.
1. produces disgust. Because microorganisms promote the changes (decomposition) of various ingredients in food during the process of growth and reproduction, and change the original sensory characteristics of food. It makes people feel disgusted.
For example, protein can produce organic amines, hydrogen sulfide, mercaptan, malodor, fecal odor and so on. In the process of decomposition, these substances have the unique smell of protein decomposition; Bacteria and fungi will produce pigments in the process of reproduction, which will make food show all kinds of abnormal colors and make food lose its original color and flavor; The "spicy taste" of fat rot and the special smell produced by carbohydrate decomposition are often unacceptable.
2. Reduce the nutritional value of food. Because after food spoilage, the structure of protein, fat and carbohydrate changed, and the original nutritional value was lost. For example, protein produces low-molecular-weight toxic substances after corruption and decomposition, thus losing the original nutritional value of protein: fat is decomposed into carbon-based compounds, low-molecular-weight fatty acids, aldehydes, ketones and so on. , lost the physiological function and nutritional value of fat to human body.
Carbohydrates deteriorate and decompose into alcohols, aldehydes, ketones and carbon dioxide, and also lose their physiological functions. In a word, the nutritional value of food is reduced because of the decomposition of nutritional components.
3. The whole process of food poisoning or potential harm from production to sales is very small, and the way and degree of food pollution are also very complicated. There are many kinds of toxic substances produced by food corruption, so the harm of spoiled food to human health is also different.
Baidu Encyclopedia-Food Corruption