Many consumers have found that when buying grapes, blueberries and other fruits, they often see a layer of "white frost" on the surface of the fruit, and it is very difficult to clean. The network rumors that these "white creams" are pesticide residues. In fact, these "white creams" are waxy or fruit powder on the surface of fruits, which are harmless to human body.
The reporter noted that the scientific interpretation of the hotspots of agricultural products quality and safety, edited by the China Food Safety 30 Forum Expert and the Researcher of the Chinese Academy of Agricultural Sciences Li Xiangzhou, pointed out that scientists have identified the chemical composition of these waxy crystals by chromatography and other analytical methods, mainly It is glucose, fructose, aliphatic compounds and some yeasts, plant active ingredients and the like. In 2015, the China Food News and other media once again stated that the “white frost†on the fruit skin is not only a pesticide residue, but a sign of the freshness of the fruit.
Like human skin, the epidermis of most angiosperms is covered with a layer of keratinocytes. Some fruits (such as grapes and plums) and some stems and leaves (such as sugar cane) deposit a layer of wax outside the keratin membrane. . The "white frost" on the fruit is called "fruit powder" or "waxy crystal", which is the waxy deposit of the epidermal membrane of the plant epidermal cells. It is a self-assembled wax crystal. These "white frosts" vary between different growth stages of the same species, even between different varieties of the same species. In addition, environmental factors also induce changes in wax composition and content. Plant surface wax is the main barrier to prevent water evaporation, and has a positive effect on plants adapting to the drought environment. Therefore, "white cream" is a fresh sign of fruit and represents less pesticide. In addition, it helps plants resist UV radiation, and because of the insoluble nature of wax, it can avoid the formation of a moist environment, thus avoiding the infection of pathogenic bacteria. From this perspective, the "white frost" of fruit is like a "safety barrier" produced by oneself.
The "white cream" on the peels such as grapes, blueberries and plums is mainly composed of the pentacyclic triterpenoid oleanolic acid, which accounts for 60% to 70%. Studies have shown that pure oleanolic acid is light yellow crystal, insoluble in water, non-toxic and has been proven to have liver, anti-cancer and anti-viral activity. It can be seen that "white frost" is not harmful to the human body.