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Keeping food cold is a great way to make it last longer. Low temperatures slow chemical reactions and the growth of microbes that spoil food.
Lowering the temperature by just 10 degrees Celsius can almost double how long vegetables stay fresh. Which is why, where my mother shopped for produce every two or three days in our fridge-less 1980s, I tend to do one run for the week. But there is a rider: refrigeration works best if one doesn’t just shove produce wherever there is space in the fridge (as tempting as that may be). Different fruits and vegetables actually have very different ideal storage temperatures.
These are, after all, still-respiring plant parts that contain live enzymes that are still reacting to their surroundings. This is why certain fruits don’t ripen well in a fridge; and why others need refrigeration almost constantly.
A simple thumb rule: if a fruit is climacteric (ripening after it is harvested), keep it at room temperature until ripe, then refrigerate, for best results. If a fruit is harvested ripe, chill as soon as possible. Grapes, cherries and berries are all non-climacteric. Climacteric ones include bananas, pears, tomatoes and mangoes.
Bananas, for instance, flourish in warm temperatures and experience “chilling injuries” in the refrigerator. Low temperatures cause their skins to turn black faster; the flesh can still be eaten, of course, but the whole thing goes better if one lets this fruit ripen outside the fridge first.
Another notoriously temperamental fruit is the avocado. It produces ethylene gas as a ripening hormone, but never produces this when one would like, and certainly overdoes things with the ethylene once it gets started. This one is best ripened outside the fridge too.
Root vegetables should not be refrigerated at all. The sturdy potato, for instance, takes cool temperatures as a sign that winter is coming, and begins converting some of its starches into sugars, for some natural “antifreeze”, thus altering taste and texture. Store in a cool (not cold) dark place instead.
Another family that rarely needs refrigeration (but for their green, leafy parts) are the alliums: onions, garlic, shallots, leeks, scallions, chives. These last longer and have better textures when stored outside the refrigerator. Refrigerating onions in particular can make them soft and mouldy, because the cold breaks down their cellular structures. Garlic, meanwhile, can turn rubbery in the fridge, as the low-humidity environment causes it to dehydrate.
This family needs no mollycoddling. Left alone, their sulphur compounds can keep them from spoiling at room temperature for weeks, even months, by inhibiting the growth of bacteria, mould and other microorganisms.
One sub-set of vegetables that definitely does benefit from repose in a crisper are leafy greens. These wilt easily due to transpiration, a process in which water evaporates from the leaf’s surface in hot and dry conditions. The loss of water content causes the leaves to lose turgor pressure (the pressure exerted by the water in each cell, which contributes to the firmness of a plant’s structure), become flaccid and droop. This wilted appearance is a sign that the plant is struggling to maintain its internal water balance.
The cool of a crisper can help. But refrigerators also typically have low humidity levels, to prevent the growth of mould and bacteria. Which is why the leaves need to be in the crisper and not elsewhere in the refrigerator. This vegetable drawer essentially creates a contained, cool space that locks in the moisture of the leaves, rather than having it leeched away by circulating dry air.
Despite these efforts, if leaves appear flaccid after a while, it can help to place them in cool water for 20 minutes before cooking. The vascular system absorbs the water and turgidity levels can return to almost-normal (though a cold bath can do nothing to restore damaged and decayed leaves; those must be discarded).
That’s the broad-brush guide to produce care. Before we end, a note on bread. You may have heard that it is better to freeze rather than refrigerate a loaf, and this is true. The air in a fridge, even in the crisper, is too arid for bread and will turn it dry and stale. The freezer, however, turns the water in the bread to ice, preventing it from escaping.
Later, when one toasts or microwaves the frozen bread, the locked-up ice turns back into moisture, keeping the bread as close to fresh as possible. I would not recommend re-freezing thawed bread, though. Between the disruptions to its cellular structures, and the starch’s attempts to retrograde (or shed the water it has embraced), its texture deteriorates with every cycle.
One final tip on the bread: Whatever you do, don’t share these hacks with the French.
(To reach Swetha Sivakumar with questions or feedback, email upgrademyfood@gmail.com)
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