The structure of tea polyphenols determines that they have good antioxidant activity. Tea polyphenols contain a large number of thick ring aromatic hydrocarbons, most of which are polyphenols containing multiple orthohydrates, have a strong hydrogen supply capacity, can remove reactive oxygen species in the environment, reduce the formation of oxygen radicals and capture the peroxidation radicals produced during oxidation. Metal ions have a catalytic effect on oxidation reactions, metal ions encounter tea polyphenols, will chelate with their orthophenol hydroxyl groups, thereby reducing the catalytic effect on oxidation reactions. In addition, tea polyphenols can bind to the oxidase in the reaction system to form a complex, thereby reducing the catalytic effect of the enzyme on the oxidation reaction.
For storage in aquatic products
Aquatic products are an important part of human food structure, with a wide variety and rich nutrition, so they are loved by consumers. However, aquatic products and their products are prone to deterioration during processing and storage. The main cause of spoilage in aquatic products is bacterial infestation, the main bacteria are pseudomonas. Under refrigeration conditions, the addition of tea polyphenols can significantly reduce the total number of bacteria in plum fish balls, so that the volatile salt-based nitrogen content and pH value are at a relatively low level. Tea polyphenols can better maintain the freshness of aquatic products during refrigeration and inhibit the oxidation of myofibrin during refrigeration of aquatic products.
Tea polyphenols mainly affect the synthesis and energy metabolism of important components such as bacterial nucleic acids and phospholipids by destroying the structure of bacterial cell membranes, hindering the normal expression of proteins, thereby affecting the composition of cell structure and enzyme activity, and ultimately causing bacteria to lose normal physiological functions and play a fresh-keeping function.
It is used for storage in meat and meat products
Meat in the process of processing, storage often due to the breeding of bacteria and spoilage, the need to add preservatives to achieve freshness. With the continuous improvement of people's awareness of food safety, the bio-preservative tea polyphenols have been widely used. Tea polyphenols can significantly inhibit the growth of microorganisms in pork, inhibit lipid oxidation, delay the deterioration of pork quality, and maintain good edible quality, thereby achieving freshness. Tea polyphenols have a strong antioxidant effect, which can well reduce the acid price and peroxide value, and at the same time can improve the brightness and yellowness of the beef meat stick, reduce the rate of redness decline, and achieve the effect of color preservation and color protection. Tea polyphenols have obvious antioxidant effects on ground beef, and according to the change of carbonyl price, the appropriate range for the addition of tea polyphenols is 0.15 to 0.225 g/kg.
The reason why tea polyphenols can play a good role in meat products and delay the process of spoilage and deterioration is mainly because of its bacteriostatic properties, which can inhibit the proliferation of a variety of bacteria, thereby reducing the reaction rate of fat oxidation, delaying the process of meat spoilage, and prolonging its freshness period.
For storage in fruits and vegetables
Fruits and vegetables are the world's second only agricultural products to grain, rich in water and various nutrients, and are susceptible to microbial contamination and mechanical damage after picking, which in turn leads to spoilage. Fruits and vegetables themselves also carry out respiration, the stronger their respiration, the more nutrients are lost, the worse the edible quality, and the shorter the shelf life. Therefore, it is necessary to adopt appropriate methods to store and preserve freshness. The fruit preservatives commonly used in China are parahynthene, carbendazim, turkdo, benet, methyl tolbuzin, sulfur dioxide and sec-butylamine, which are chemical fungicides, and there is a possibility of carcinogenicity or potential carcinogenicity, mutagenicity and teratogenicity.
Tea polyphenols as a biological food preservative, with a broad spectrum of antibacterial, natural, efficient and non-toxic and other advantages, it is reported that spraying low concentration of tea polyphenol solution on the surface of fresh fruits and vegetables can reduce their respiratory intensity, inhibit bacterial reproduction, slow down pigment degradation, maintain the original color of vegetables and fruits; but also reduce the degradation of vitamin C, prolong the shelf life, maintain nutrition.
For storage in grease
After storing fresh soybean oil for 30 d, the peroxide value will change greatly. Eating raw oil with excessive peroxidation value will endanger the health of consumers, so it is necessary to add a certain amount of antioxidants to the oil. Tea polyphenols have strong antioxidant properties, and have a good antioxidant effect on soybean oil, lard, etc., and their antioxidant effect is related to the concentration of tea polyphenols. LtP was added to fresh lard, and the changes in peroxide value were compared with the raw tea polyphenols and synthetic antioxidants, and the results showed that the antioxidant efficiency of LTP and TBHQ was close, and its effect was better than that of unmodified TP and BHA. The antioxidant effect on hemp seed oil shows that LTP has a good antioxidant effect and is better than BHT.
The hydroxyl group of tea polyphenols acts as a hydrogen donor to bind free radicals in fatty acids, interrupting the chain reaction of fatty acid oxidation and inhibiting the formation of hydroperoxides. At the same time, fat-soluble tea polyphenols can chelate the trace amount of valence metal elements in oils and fats, so that their catalytic activity is lost, and the free radical chain reaction can be terminated from the source. In addition, the phenolic hydroxyl group itself is also prone to oxidation, thereby reducing the oxygen content in the oil and delaying the oxidation of the oil.
It is used for storage in pastries and dairy products
Tea polyphenols can also be used in pastries and dairy products. For high-fat cakes (cakes, mooncakes) and dairy products (cheese, milk powder), adding an appropriate amount of tea polyphenols can make them maintain their original flavor, and can inhibit the growth of bacteria, prevent spoilage, and prolong the shelf life of food. At the same time, it can also effectively remove the sweet "sour tail" and achieve the effect of sweet taste.