These two kinds of fruits cannot be kept fresh in a vacuum?

Do you think you can keep fruits fresh by sealing them in vacuum bags and cutting off oxygen? Far from it! When it comes to the seemingly all - purpose vacuum preservation method, bananas and grapes are true "rebels"—instead of maintaining their juiciness, they deteriorate even faster. What's the science behind this?

Let's start with bananas. As typical climacteric fruits, they rapidly increase their respiration rate and release large amounts of ethylene during ripening. In a natural environment, ethylene gradually diffuses, allowing bananas to ripen steadily. However, once placed in a vacuum bag, the ethylene has nowhere to escape. The accumulating high - concentration ethylene acts like a speed - up button, forcing bananas to respire frantically. Starch converts into sugar rapidly, and the flesh softens and turns yellow quickly. Before you can savor their sweetness, bananas go straight from unripe to rotten. Ripe bananas are even more vulnerable in a vacuum. With their fragile cell structure, the imbalance of internal and external pressure causes water to seep out in large quantities, turning the flesh into a mushy mess and creating an ideal breeding ground for bacteria.

Now, consider grapes. Their paper - thin skin is the Achilles' heel for vacuum preservation. When vacuum - packing, the sudden drop in bag pressure creates an overwhelming pressure difference between the inside and outside of the grape skin. The delicate skin can't withstand this and easily breaks. Once broken, the sugar - rich juice oozes out, ruining the taste and becoming a feast for microorganisms. To make matters worse, the vacuum environment disrupts the grapes' normal respiratory metabolism. Forced into anaerobic respiration, grapes produce substances like alcohol, which further damage the cells and spoil the flavor.

In fact, these two fruits have more suitable preservation methods. Bananas can be hung in a well - ventilated area or wrapped at the stem with plastic wrap. Grapes are best stored with their stems in the refrigerator, unwashed and away from ethylene - releasing fruits. Mastering these tips is the key to keeping them fresh and delicious.