The best thing about frozen fruits and vegetables is that they’re generally frozen within 48 hours of picking, which locks in flavor and, more importantly, nutrients.
Delicate fruits like berries are subjected to something called cryogenic freezing (which is also what they did to baseball great Ted William’s head). They use solid C02 or liquid nitrogen to quickly freeze the fruit (or head), which lessens crystallization. Other, less vulnerable fruits and vegetables are placed on conveyor belts and belted with “air blast” freezing.
It makes sense that the nutrients would be locked in place, but there’s research to back it up. Bouzari, et al., in 2014, evaluated the amount of riboflavin, beta-carotene, vitamin C, and alpha tocopherol (vitamin E) in frozen and non-frozen carrots, corn, spinach, broccoli, peas, green beans, strawberries, and blueberries (2).
Here’s what they found:
- Frozen foods showed a minimal loss of vitamin C, compared to big losses in non-frozen, “fresh” varieties.
- Frozen peas showed an increase in vitamin C and vitamin E over non-frozen.
- There was basically no difference in riboflavin content between frozen and non-frozen samples.
- Three of the frozen vegetable varieties had higher amounts of vitamin E than their non-frozen counterparts.
- The findings were true for fruits and vegetables even if they’d been frozen for 90 days.
The news wasn’t all a bowl of frozen cherries, though. For reasons unknown, the frozen peas, carrots, and spinach had lower levels of beta-carotene than the non-frozen samples.
Generally speaking, though, as long as the “chain of freezing” wasn’t broken (e.g., some grocery store twit let the frozen produce sit on a loading dock for a couple of hours while they went to see a Spiderman movie), the frozen produce is often as good or better than fresh, and another study shows that the nutrient levels remain stable for at least 6 months (3).
The same is true for most, if not all, the phytochemicals found in fruits and vegetables (4). In fact, in the case of blueberries, freezing actually improves the bioavailability of anthocyanins (5). Apparently, the freezing sometimes creates crystals that disrupt the structure of the plant tissue, thereby making the anthocyanins more accessible.