Every summer the same story: you buy a huge watermelon, eat a quarter, and shove the rest into the fridge where in two days it goes soft, loses its taste and ends up in the bin. A waste of money, a waste of the fruit. And the secret to making it last longer is no magic at all - just a few habits most of us ignore.

The first rule is the opposite of what everyone does: don't cut the whole watermelon at once. The larger the cut surface, the faster the fruit loses water and quality. Cut only as much as you'll eat, and leave the rest whole. Second - forget the cling film and the foil. Cut watermelon keeps best in an airtight container, because it limits contact with the air far better than ordinary wrapping.

The third is temperature. The watermelon should sit at 4 to 7 degrees, and not in the fridge door - there the temperature jumps with every opening. Put it on a middle shelf, in the coldest, most stable part. And always use a clean knife and clean hands: cross-contamination from dirty utensils is common, and an invisible reason why the fruit spoils faster than expected.

With these few moves, an open watermelon calmly lasts three to four days without losing its taste. If it starts to smell sour, to go too soft or to develop dark spots - then it's for the bin, no hesitation. A trifle? Maybe. But at a time when everything is getting pricier and food is thrown away by the tonne, a little care toward one ordinary summer fruit is both a saving and a small sign of respect toward what we eat.