Careful consumers found that it not only grapes surface has hoar, plums, sugar cane, blueberry and even surface layer of melon has the hoar. In fact, this layer of hoar is sugar alcohols which are secreted by fruit, and it was also known as fruit powder. They belong to the biosynthesis of natural substances, which is completely harmless to the human body. These compounds do not dissolve in water, but soluble in organic solvents such as chloroform, so no matter you use the water to soak, wash or rub, you could not completely get rid of the hoar from the peel.
This layer of fruit powder has a protective effect for fruits, such as the surface of this layer of fruit powder can reduce evaporation, thereby preventing rapid dehydration shrinkage after picking, which have the positive effect to adapt arid environment. The characteristics of hoar could not soluble in the water, so it could let grape surface to avoid moist environment, thereby reducing the pathogenic infection. Surface hoar on grapes also contain yeast, so when you do the wine, you should not add another yeast. We need to explain hat grapes are difficult to have pest, and now planter use bagging to grow. This means that the probability to use pesticide is very small, so if it is determined that the hoar grape itself is not necessary to wash.
For a certain extent, hoar is a sign of fresh grapes, but cannot avoid some merchants to spray pesticide. Specific distinction is that the normal “hoar” naturally distributed and does not cover the color of the skin of grapes, which make the grapes look more beautiful. And if it is a pharmaceutical “hoar”, the appearance is not distribution, which will have a dark blue mark.
Actually, bayberry, cherry, strawberry and so on has the similar characters. They are relatively soft, but are very inconvenient to clean. The best way is to put these fruits in rice water and soaked in salt water about 5 minutes. Their role is different, alkaline rice water could decompose the pesticides and dilute brine can make the parasites out from these soft fruits.