There’s something intuitively appealing about fresh produce. A freshly made salad, with freshly picked veggies — so refreshing and light!
On the flip side, preserved produce have long been the unwanted stepchildren of the produce family. But what exactly happens to nutrients when fruits and vegetables are canned or frozen?
Before we take a look, first at fresh produce, then at frozen produce, and finally at canned produce, let’s have a word about bioavailability.
Some micronutrients are bound in our food so tightly that our bodies can’t shake them loose for digestion. Others are just hard for our bodies to absorb. The ease with which a nutrient comes loose and gives up its goodies to our bodies is known as its bioavailability.
Cooking can increase the bioavailability of some nutrients and decrease that of others, and so can meal composition. For instance, it’s easier for our bodies to absorb fat-soluble vitamins (A, D, E, and K) if we eat them with fats. In other words, the compounds in and around fruits and vegetables can affect, positively or negatively, the bioavailability of their nutrients.
We can describe a fruit or vegetable as fresh if it’s either “postharvest ripened” (i.e., if it ripens during transport) or “vine ripened” (i.e., if it is picked and sold ripe, as at a farm’s fresh market or a farmer’s roadside fruit stand).
You might expect vine-ripened produce to be more nutritious, since it has more time to absorb nutrients from the soil — and in some cases, it is. But plants absorb a large percentage of the most crucial minerals during the early stages of growth, and fruits and vegetables can still synthesize macronutrients and micronutrients during postharvest ripening.
Several studies suggest that postharvest-ripened produce is nutritionally equivalent to vine-ripened produce — and in some cases, even better. The nutritional content of either kind of produce will depend on a host of other factors, including soil, season, weather, farming method, and storage conditions and duration.
Vine-ripened produce isn’t necessarily more nutritious than postharvest-ripened produce. Much of a produce’s nutritional content depends on other factors, starting with soil quality.
In general, frozen produce is fully vine ripened and undergo only minimal processing. Most vegetables and some fruits undergo blanching in hot water for a few minutes before freezing, in order to inactivate enzymes that may cause unfavorable changes in color, smell, flavor, and nutritional value.
Although blanching can leach out minerals and break down biomolecules like vitamins, postharvest-ripened produce and blanched frozen produce have very similar overall nutritional content. The main impact of blanching seems to be on taste: certain fruits and vegetables have that unique just-picked flavor, which the blanching-freezing process greatly reduces.
Frozen fruits and vegetables are minimally processed.
Canned fruits and vegetables are usually vine ripened, like frozen produce, but they tend to undergo a lot more processing. Blanching is common, but so are the placement in syrup, the addition of salt, and the introduction of additives that carry health risks of their own.
Moreover, some cans are lined with bisphenol-A (BPA), a chemical associated with heightened risk of cancer, and both the acidity of the produce (e.g., tomato sauce) and the heat from sterilization can help BPA leak into what you eat. (You can read more about BPA in this article from ERD 6).
Fruits and vegetables reach your store’s shelves through a variety of methods, each of which has its pros and cons. Furthermore, the method that works best for one type of produce may not work best for another. And at the end of the day, different ways of cooking can have a much bigger impact on the produce’s nutrient content and bioavailability.
The best method is the one that gets you to eat your veggies. Whether they’re fresh, frozen, or canned, if you eat enough fruits and vegetables every day, you’re going to reap some of their nutritional benefits.
- Nitrate and nitrite nitrogen in fresh, stored and processed table beets and spinach from different levels of field nitrogen fertilisation. J Sci Food Agric. (1971) Lee CY, et al.