Food antioxidants and their application technology

Food antioxidants and preservatives are used in food preservation and storage, but preservatives are for microbial reproduction and enzyme activity of the impact and inhibition. The basic aim of antioxidants is to delay the deterioration caused by food oxidation, and the test of the use effect is different from that of preservatives, the test of the use effect is different from that of preservatives. The antioxidant effect is determined by the test of peroxide value, acid value, carbonyl change and other parameters. In addition, antioxidants are different from pharmaceuticals or health products, only as accessories added to processed food or raw materials.

Mechanism of action of antioxidants

1. The mechanism of antioxidant is complex and there are many possibilities

(1) the consumption of residual oxygen, a kind of antioxidant, by means of reduction reaction, reduces the oxygen content in and around the food system, which can be said to stop at the source. In other words, antioxidants themselves are highly oxidizing, so in the presence of factors that oxidize food (such as light, oxygen, heat, etc.) , antioxidants react with oxygen in the air to avoid oxidation of the food. Ascorbic acid, for example, removes oxygen from food, which itself is oxidized to Dehydroascorbic Acid.

(2) chelating metal ions, in which oils contain trace metal ions, especially heavy metal ions in bivalent or high valent states. They have suitable redox potential, which can shorten the initiation period of radical chain reaction and speed up the oxidation rate of esters. And this kind of antioxidant can reduce the metal ions through the chelation of metal ions to promote oxidation. Such as EDTA, citric acid, etc. .

(3) the most effective way to block lipid oxidation by absorbing free radicals is to scavenge free radicals. These antioxidants may combine with oxidation intermediates in the oxidation process to turn the free radicals produced by oil oxidation into stable products, thus preventing the oxidation reaction from proceeding. Such as Butylated hydroxyanisole, propyl gallate, vitamin E, etc. . In general, oxygen in the air binds to fat molecules to produce Roo · Radicals, which are then absorbed by a radical absorber to form a hydroperoxide, which provides a hydrogen donor AH. Phenolic antioxidants and lipid radical have been shown to produce relatively stable free radicals. The free radical a of the antioxidant is not active, it can not cause chain reaction, but can participate in some termination reaction. Another free radical, R · , produced by lipid oxidation can be eliminated by the electron acceptor of the free radical absorber. In biological tissues, vitamin K is an electron acceptor and directly eliminates R · Radicals.

(4) breaking off antioxidants such as peroxides, which bind to the peroxide formed during the oxidation of fats and oils, and cracking them into new stable compounds such as dilauryl thiodipropionate.

(5) the activity of oxidases can be inhibited or weakened by antioxidants, which can scavenge superoxide free radicals. In living organisms, esters are oxidized by various free radicals to produce peroxides. Enzyme antioxidants such as xanthate oxidase can react with the resulting peroxide to form superoxide radical O2, which in turn is Superoxide dismutase to form hydrogen peroxide. Hydrogen peroxide is Catalase into oxygen and water.

二、Classification of antioxidants

At present, there is no uniform standard for the classification of food antioxidants. Because the classification basis is different, can produce the different classification result. Antioxidants can be divided into synthetic antioxidants (such as BHA, BHT, PG, etc.) and natural antioxidants (such as tea polyphenols, phytic acid, etc.) . Antioxidants can be divided into oil-soluble, water-soluble and compatible according to their solubility. Oil-soluble antioxidants include BHA, BHT and so on; water-soluble antioxidants include Vitamin C, tea polyphenols and so on; compatible antioxidants include lipoic acid and so on. Antioxidants can be divided into Carotenoid antioxidants, vitamin antioxidants, polyphenol antioxidants, flavonoid antioxidants, and enzyme antioxidants according to their chemical structure. Antioxidants can be divided into free radical absorbers, metal ion chelators, oxygen scavengers, peroxide decomposers, enzyme antioxidants, UV absorbers or singlet oxygen quenchers. Free Radical absorbents are substances that can block the chain reaction of free radicals in oil oxidation. They are generally phenolic compounds, which have the function of electron donor, such as Butylated hydroxyanisole, 2-tert-butylbenzene-1,4-diol and tocopherols. Enzyme antioxidants include enzymes such as glucose oxidase, Superoxide dismutase (SOD) , Catalase, glutathione oxidase, etc. , their role is to remove oxygen (such as glucose oxidase) or peroxide from food (such as SOD) . At present, our country does not include this kind of enzyme antioxidant in the range of food antioxidants, but in the enzyme preparation part.

三、The selection principle of antioxidants

Antioxidants that can be used in food should meet the following requirements. 

(1) it has excellent antioxidation effect. The food antioxidant activity is outstanding, the antioxidant capacity is big, its anti-oxidation ability is high, may realize at the low concentration plays the high-effective anti-oxidation function. 

(2) the products are non-toxic and harmless. The safety of food antioxidants is an important index to be considered. The first principle of choosing food additives is to have low toxicological requirements, be harmless to human body and not be digested and absorbed.

 (3) it has good stability and coexists with food, and has no influence on the sensory properties of food (including color, aroma, taste, etc.) . 

(4) the utility model is convenient to use and the price is cheap. According to different grades of food and types and antioxidant effect, choose cheap and effective antioxidants, which is conducive to reducing the cost of processed food.

四、Points for attention in the use of antioxidants

(1) choosing appropriate adding time from the mechanism of antioxidants, we can see that antioxidants can only hinder lipid oxidation, delay the time when food begins to go bad, but can not change the consequences of already bad, therefore, antioxidants should be added as early as possible in order to play the role of anti-oxidation.

(2) there is not always a positive correlation between the amount of antioxidant and the antioxidation effect. When the antioxidant concentration is higher than a certain level, the antioxidation effect will not be enhanced, on the contrary, it has the effect of promoting anti-oxidation. The amount of antioxidants in line with the national standards for the use of food additives.