What are the types, applications and development trends of food preservatives?

Food preservation has been closely related to human life since ancient times. Human beings have long used pickling, wine soaking and other methods to treat food preservative treatment. With the rapid development of social economy and the sharp growth of food demand, a large number of food needs long-distance transportation and reprocessing, simple traditional anticorrosion methods no longer meet the needs, food preservatives came into being. Food processing with food preservatives can inhibit the growth and reproduction of microorganisms, so as to prevent food spoilage and achieve the purpose of extending the preservation time of food.
Mechanism of food preservatives
It is generally believed that the preservative function of food preservatives is achieved by destroying the cell structure of microorganisms or interfering with their physiological functions. For example, the integrity and normal functioning of cell wall and cell plasma membrane, metabolic enzymes, nucleic acids and protein systems are necessary for microbial growth and reproduction, so food preservatives can cause microbial death or stop growth as long as they interfere with any one of the links.
Types of food preservatives
According to the source, food preservatives can be divided into chemical preservatives and natural preservatives.

2.1 Chemical Preservatives Preservatives synthesized by chemical reflection are called chemical preservatives. Chemical preservatives have the characteristics of high efficiency, convenience and low cost, and are the most widely used preservatives in our country, including acid, fat and inorganic salt preservatives.
2.1.1 Acid preservatives Commonly used acid preservatives are benzoic acid, sorbic acid and propionic acid and their salts… . Acid-type preservatives can inhibit bacteria through undissociated molecules under acidic conditions, and their preservative effect is related to pH. The reason why acid preservatives can inhibit bacteria and preservatives is that they will interfere with the enzyme system of microorganisms and make them unable to perform normal metabolic functions. At the same time, acid preservatives can inhibit the permeability of cell membrane and inhibit the growth and reproduction of microorganisms.
Benzoic acid in acid preservatives is cheap and widely used in daily life products such as soy sauce and cosmetics, but the toxic side effects of benzoic acid and its salts have been controversial. Sorbic acid has a strong inhibitory effect on mold and yeast, is recognized as a high-efficiency and low-toxic preservative, has no effect on food flavor, and is usually used in flour, fish, eggs and other raw materials processed into food.
2.1.2 Ester preservatives Ester preservatives refer to paraben esters, which are commonly used in China, such as p-hydroxybenzoic acid, ethyl ester and propyl ester. The mechanism of ester type preservative is to destroy the cell membrane of microorganisms, denaturate and deactivate the proteins in the cells, thus destroying the normal physiological balance of microorganisms. Ester type preservatives are mainly used in vegetables and fruits preservation, and the bactericidal effect is stronger than acid type preservatives, and its preservative effect will not change because of the change of pH, which can be rapidly and completely absorbed in the gastrointestinal tract, and can be hydrolyzed to hydroxybenzoic acid, and is discharged from the urine, not stored in the body, so the toxicity is relatively low.
2.1.3 Inorganic salt preservatives Commonly used inorganic salt preservatives include nitrates, nitrites and sulfur-containing sulfites. This kind of preservative is mainly by inhibiting the activity of microbial respiratory enzymes and causing the death of microorganisms by hypoxia. Inorganic salt preservatives can not only keep food fresh, but also play a role in increasing color. For example, nitrite can not only inhibit the growth of botulism, but also keep fish and meat fresh and color, mainly used in meat pickling.
2.2 Natural preservatives Natural preservatives are generally extracted from animals, plants and microorganisms or their metabolites, a class of substances with antibacterial and preservative effects, safer than chemical preservatives, mainly including animal source, plant source and microbial source natural preservatives three categories.
2.2.1 Natural preservatives of animal origin Natural preservatives refer to substances with antiseptic effect artificially extracted in some animals or their metabolites, such as protamine, chitin and propolis. Protamine is mainly polyarginine or polyarginine and a few other amino acids in its molecules to bind to the bacterial cell wall in a certain structure or form, and inhibit the formation of the cell wall, thereby inhibiting the metabolism of the cell and causing cell death. At present, it is mainly used in milk and bread and other foods.
2.2.2 Natural preservatives of plant origin Natural preservatives refer to substances with antibacterial and preservative effects extracted from plant roots, bark, seeds, etc., such as spices, some Chinese herbs and plant essential oils. Because of the unique geographical environment in China, the resources of Chinese herbal medicine are very rich, and the substances extracted from Chinese herbal medicine as preservatives have broad research prospects in China. Among them, plant essential oil contains a large number of secondary metabolites, which has the effect of delaying or inhibiting the growth of bacteria, yeast and mold. It is mainly used for the preservation of beef, fruits and vegetables.
2.2.3 Natural preservatives from microorganisms Some microorganisms or their metabolites in nature have antibacterial and preservative effects and can be used as preservatives, such as lactostreptococcus, kojic acid, etc. Among them, lactostreptococcin can be digested into amino acids by proteolytic enzymes in the digestive tract after being eaten by the human body, with high safety. It is the first antibiotic used in food preservation in the world, mainly used in the preservation of various dairy products; Kojic acid has the function of scavenging free radicals, enhancing cell vitality, protecting food color, etc., and is widely used in medicine and food fields.