When you pick a fruit or vegetable, it is still a living, breathing thing. It respires, taking oxygen from the air and releasing carbon dioxide.
But it can’t live indefinitely. A peach, lettuce or bean, once cut, can no longer make food by means of photosynthesis, and begins to draw down its stored reserves. It no longer receives water from the soil, although its pores continue to release water vapor, costing it firmness and fullness. Mighty antioxidants like beta carotene and lycopene, prized guardians of own personal shelf lives, start to lose their clout.
Some types of produce keep better than others. The decline and fall of a butternut squash might take eight months. A basket of spinach on a hot day might not last eight minutes.
There is much you can do to keep produce lively. Commercial crops, which must be stored for days and hauled for miles, are treated to a regimen as detailed as an Elizabeth Arden Day of Beauty. At home, the process is greatly simplified.
When you pick fresh food, the proper mindset is essential. I am not the touchy-feely sort, but I do think it helps to imagine a vegetable or fruit as a sentient being that will scream “Ouch!” if handled roughly. Dings, nicks or bruises provide entry points for bacteria and fungi — the handmaidens of rot. Greens should be cut with a sharp knife, not ripped from the plant. Zucchinis should be gently placed in a harvest basket, not dropped, lobbed or flung. Tomatoes piled eight deep in a bucket, or rolling around in the back of the car, will suffer internal injuries that are routes to decay.
Timing also plays a part. Clearly the best time to pick food is just before you eat it, before the aging process has begun. Fresh food fanatics keep a hose in the garden so that they can instantly pick, wash and nibble. But often you must pick more than you need, to keep a crop producing. Even if you have canning, freezing and gift-giving down to a science, something will need to be stored.
It is important to prevent as much moisture loss as possible. If you pick on a hot, sunny day, when the produce looks limp, it will have trouble bouncing back. Early morning is best.
What you do next depends on whether a crop is a cool weather or hot weather one. Those that thrive in the tropics, such as tomatoes, watermelons, peppers, eggplant and bananas are best stored above 50 degrees F. Some actually decline in flavor, color or food values when refrigerated.
Most crops that thrive in cool areas or during cool seasons need chilling if not eaten right away. These include all the leafy greens, cole crops such as broccoli and Brussels sprouts and some northern fruits, especially berries. Cooling keeps these fresh and alive in three very important ways: it reduces moisture loss by slowing down transpiration, it preserves oxygen levels by slowing plants’ respiration, and it reduces the effect of ethylene, a colorless gas naturally present in fruiting bodies, that enables them to ripen.
Leafy crops, with their large, porous surfaces, are the most at risk. Plunging them into a sink full of cold water will rehydrate them, get rid of “field heat” and hasten the exit of insects that would otherwise stay around to dine.
When storing vegetables, you must also walk a fine line between giving them too much air and water, and too little. A bag that is too tightly sealed will accumulate excess carbon dioxide from respiration, which affects quality, and excess moisture, which hastens decay. A crisper drawer works fine or, better yet, a lettuce spinner, which lets the greens drain gently while they are cooling. It pays to own several.
Whether to wash produce before storing depends on the crop. Root cellar vegetables like potatoes and carrots keep better if stored grimy, then washed before eating, although I do wash carrots stored for immediate consumption — scrubbing is easier if done promptly. All squash keeps better unwashed — though I remove any rotting flowers that cling. Onions and garlic should never get wet.
Good fridge management pays off. If there are two bags of something, always cook the one most recently harvested, and compost the other. Backlogged ones soon become sordid messes.
The wonderful thing about being a home gardener is that you can choose varieties of vegetables and fruits for their flavor, not ease of storage and shipment. You never have to pick them green, then ripen them. There is a day on which each one of them has reached its full potential and is perfect for eating. Seize it.
Barbara Damrosch’s latest book is “The Four Season Farm Gardener’s Cookbook.”