1, the skin of Qingma milk grape itself contains tannin. When the content is high, it will taste astringent. The reason for this situation is that grapes are picked too early, and their physiological maturity has not been reached, or some grape varieties are particularly rich in tannins and have a heavy astringency after maturity.
All varieties of grapes have a common feature, that is, the fresher the better. When selecting fresh grapes, it should be noted that there is a layer of frost on the surface of fresh grapes, which will fall off when touched by hand, so grapes without frost may be picked and left, and all the frost will fall off. What's more, grapes with green skins can't see hoarfrost, so this method is not applicable; Fresh grape stems are tough, and stems and fruit grains are strong. When fruit stalks and grains are stored for a long time, they will be broken.
Basis for judging whether grapes are "ripe" when buying:
1, see if there is frost on the grape surface.
Grapes that are normally ripe on ordinary trees will have a thin layer of hoarfrost on their surfaces. The scientific name of hoarfrost is fruit powder, which is glucose powder in the ripening stage of grapes and is harmless to human body. It looks like there is a layer of ash on it, but this grape is fresh and grows naturally. The thicker the frost, the better the grapes, indicating that the grapes are fully mature. And if you meet a grape with a smooth surface, not only frost-free, but also particularly shiny, it may just be stale or ripe, so don't buy this grape again, and the boss won't eat it himself.
It is worth mentioning that some green grapes cannot see hoarfrost, so this method cannot be used.
2. Look at these vines
Normal and mature grapes, fresh grapes just picked or picked soon, the vines must be green or light yellow, and the vines are thin and tough, so that more than a dozen bunches of grapes will not fall off. If the vines are brown, it proves that the grapes have been put for a long time and are not so fresh. When it comes to vines, the fruit will falter or even fall off. Seeing that the vines are much thicker, don't buy this kind of grapes. During the spraying process, some chemicals may be spilled on the vines. Pay attention to this place when buying grapes.
3. Look at the color of the grapes
When buying grapes, don't just look at the face value. Looking good is often not really good. Normal grapes are difficult to have the same color because of the different light receiving areas. Generally, the inside is greener and the exposed side is darker. Many ripe grapes have the same color, because they are not matured normally, but matured under the stimulation of maturity, so the color will look very ripe, but in fact time is far from enough. If you see that the color is similar and looks mature when you buy it, it is recommended not to buy such grapes.
4. Look at its grape skin
When we see many cracks on the grapes, many people will think that the grapes are completely ripe and will taste sweet. So there are still some people who choose this grape, but this idea is wrong. Most grapes are covered with cracks, which means that grapes with ripening agents or swelling agents will grow faster and become bigger. However, because of the rapid growth, the grape skin can't keep up with the growth speed, so the grape skin will crack under pressure, so there will be cracks on the surface. We'd better not have this grape.