Antioxidants can be used as hydrogen donors to scavenge free radicals generated during the chain initiation stage, thereby inhibiting or reducing the oxidation of oils. Therefore, in order to delay the oxidation of fats and extend their shelf life, the most common and effective way is to add antioxidants to the fats.

Natural antioxidants are extracted from animals and plants, and have the characteristics of high safety, strong antioxidant capacity, no side effects, antiseptic and fresh-keeping.

Natural antioxidants can be divided into radical absorbers, metal ion chelating agents, oxygen scavengers, singlet oxygen quenchers, hydroperoxide decomposers, ultraviolet absorbers, enzyme antioxidants, etc. according to their mechanism. Common natural antioxidants are mainly divided into the following categories:

Flavonoids are a kind of low-molecular-weight natural plant components with 2-phenylchromone structure that exist in nature. They cannot be synthesized by the human body and must be ingested from the outside world. There is a ketone carbonyl group in their molecule. The oxygen atom in the first position is basic and can form salts with strong acids. The hydroxyl derivatives are mostly yellow, so they are also called flavones or flavonoids.

1. Chelate metal ions, can form chelate with metal ions, reduce the catalytic activity of metal ions, hinder the occurrence of oxidation reaction, and can well remove reactive oxygen species (ROS) and reactive nitrogen substances.

2. Scavenging free radicals, providing hydrogen atoms to hydrogen peroxide free radicals to generate stable hydroperoxides, and the phenolic hydroxyl groups in the molecules react with oxygen free radicals to form conjugated and stable semiquinone free radicals, interrupting free freedom Base chain reaction.

Polyphenols are a collective term for a group of chemical substances in plants, named after having phenolic groups. It can be divided into two categories, one is polyphenol monomers, including chlorogenic acid, ellagic acid and some complex polyphenol compounds containing glycosides; the other is oligomers or polyphenol monomers polymerized Polymers are collectively referred to as tannins.

1. The antioxidant activity of tea polyphenols is 2.6 times that of butylated hydroxyanisole (BHA) and 3.6 times that of vitamin E. Since tea polyphenols are water-soluble, they need to be modified into oil-soluble type to better play a role in oils and fats.

2. Resveratrol is mainly derived from peanuts, grapes (red wine), polygonum cuspidatum, mulberry and other plants. Resveratrol is a polyphenol compound that is effective for longevity protein-deacetylase (sirtuins). Known for activation. Sirtuin is an important factor in delaying cell senescence and prolonging life by regulating various cell processes. Sirtuin's inhibition of cell senescence is mainly mediated by delaying age-related telomere loss, maintaining genome integrity and promoting DNA damage repair.

Natural pigment contains a large number of phenolic hydroxyl groups, so it has efficient hydroxyl radical and peroxy radical scavenging ability, and also has strong reducing properties, which can quench singlet oxygen. It is a potential natural oil antioxidant. Its anti-oxidation The capacity is several times that of vitamins (such as vitamin C and vitamin E). Common natural pigments are β-carotene, lycopene, astaxanthin and so on. The disadvantages of natural pigment antioxidants are poor water solubility, difficult toning, and easy to change color.