All plants form a large number of phenolic substances in their metabolism. Therefore, all food products of vegetable origin always contain various phenolic compounds of different quality and quantity. Phenolic compounds give the unique taste and color of vegetables and fruits. Fenolk compounds are important in many respects to human health as a food component. For example, in addition to their effects on taste and odor formation, color formation of fruits and vegetables, antimicrobial and antioxidative effects, secretion of some enzymes and purity control criteria in different foods.

Phenolic compounds in plants are phenolic acids and compounds which are generally small molecule and volatile. Phenolic compounds cause unwanted color changes in foods. The most important is browning. Enzymatic browning in foods creates quality loss. Therefore, oxidation of phenolic substances is tried to be prevented during processing of vegetables and fruits.

In recent years, phenolic compounds found in foods of plant origin have been studied more intensively. Especially in terms of human health, there is evidence that it reduces cancer formation. However, the views are different.

Phenolic compounds are mainly two groups: phenolic acids and flavonoids.

Phenolic compounds have antioxidant effects. The highest antioxidant effect is observed in grape, grapefruit, tomato, orange and apple juices respectively. Phenolic compounds have positive effects on nutritional physiology.

To date, at least five thousand phenolic substances have been identified. More than two thousand of these are natural flavonoids. It is generally found in the living tissues of plants such as leaves, flowers, fruits, woody tissues and kernels. In terms of phenolic substances, fruits were found to be richer than vegetables. However, phenolic substances are present in more or less amounts in almost every fruit and vegetable.

In authorized laboratories, within the framework of chemical tests phenolic substances determination studies are carried out. In these studies, the standards published by domestic and foreign organizations are complied with.