Welcome back! We’re continuing our discussion on whether you should eat fresh, frozen, or canned fruits/veggies. So far, we’ve seen the pros and cons of fresh produce: High in nutrient density, but loses its nutrients quickly if stored for a few days! How can we combat that?? Hmmm…..??? Got it! Freeze the colorful bastards! Yes! I’m saying freeze your produce or buy frozen if you know you store food for a while. Also, you may get more nutrients from doing this. Let’s look at what the data says about frozen produce in comparison to other methods!
Last post, I did not include processing as a means of loss because fresh fruits/veggies don’t really experience much processing that could affect nutrient availability. Time was a primary factor in losses from fresh produce. I include it here because the freezing process can have an effect on the nutrients in food.
Processing for produce involves cooking the food then quickly freezing it. This is typically accomplished through blanching. This process involves boiling the food for a very short period of time, enough to cook it. Then, the food is thrown in cold water or an ice bath to freeze! This process can yield some losses in nutrients.
For example, one study found a 63% loss of Vitamin C in green peas just from freezing the food1. Numerous studies were compared to examine the loss of Vitamin C during the blanching and freezing process. Across the board, there was a lot of variance (From 17%-63% losses). Alternatively, while broccoli and spinach showed the greatest losses, asparagus appeared to be the hardiest vegetable, as Vitamin C was shown to retain 90% of its concentration after freezing2. Most of the vegetables reviewed saw fewer losses of ascorbic acid to freezing than canning, with some veggies losing as much as 90% of their Vitamin C just from the canning process2.
Losses of B-vitamins are similar to Vitamin C in that they vary greatly between studies, but the percentages were, on average, lower in terms of percent lost to freezing. Freezing was similarly a more efficient process than canning to preserve B-vitamins2.
For the fat-soluble Vitamin A (specifically beta-carotene), their does not appear to be a major change in loss between canning and freezing; they both appear to lose about the same amount2. Vitamin A was shown, as seen through multiple studies, to have losses ranging from 5%-48%2. The authors of the review made an interesting point that the typical American’s main source of Vitamin A is through lycopene in tomatoes, and these are not normally frozen2, so this may not be a super important point if most of our intake is from tomatoes anyway!
Not much is mentioned of Vitamin E, but it appears that canning may produce a slightly greater amount of the vitamin than fresh and frozen counterparts2.
In terms of minerals, fresh, frozen, and canned veggies all were neck-and-neck. One food would have more calcium when canned, then the next would have more calcium when fresh, and so on and so on. Just from my judgement, with the exception of sodium, it seemed as though fresh and frozen produce showed, on average, higher amounts of the minerals when compared to canned counterparts3.
For fiber and processing, the only time fiber was lost was when some of the fibrous portions of the food were physically removed. There appears to be nothing about canning or freezing the affects fiber if the food is left intact2.
As one can imagine, frozen produce does much better than fresh in terms of nutrient retention during storage. Regarding Vitamin C, after one year of storage, one study saw an average decrease of 20%-50% for food such as broccoli and spinach4 whereas fresh foods can see those losses or greater in as little as 24 hours5!
Unfortunately, the data is pretty inconclusive about B-vitamin losses, so I’m not going to include it here.
In regards to Vitamin A, some studies say a small increase in Vitamin A concentration after storage6 while others saw no change or decreases after storage for a period of time7.
Data from the USDA suggest that some foods like tomatoes and sweet potatoes contain higher levels of Vitamin E when canned compared to their fresh and frozen equivalents; however, spinach and asparagus showed higher levels when fresh or frozen8. Basically, the results are inconclusive, there is no clear winner for this category.
As mentioned in the last post, fiber and minerals are much hardier components of food than the other vitamins, so losses from them are very minimal, including when they are frozen for months on end8.
Home-cooking foods can have a significant effect on nutrient losses. Generally, when heat is applied, some losses will occur, especially in the water-soluble vitamins.
When compared with canned and fresh produce, frozen held its own with fresh foods for Vitamin C retention-throughout processing, storage, and canning-being very similar in nutrient quality compared across a range of foods. Canned produce fell short, withstanding significant losses throughout the processing, storage and cooking steps2.
For the B-vitamins, it has been seen that Thiamin, a vitamin important for cell metabolism and growth9, can witness small or significant losses during the cooking process (11%-66% loss of nutrient)10. From other studies, they showed that canned and frozen produce fell equally short to fresh foods after cooking for the B-vitamins11,12.
Vitamin A one again saw increases in availability after cooking. Some of the foods saw even greater percent changes when frozen than when cooked. For example, one study saw only a 5% increase in Vitamin A for carrots when fresh compared to a 21% increase when frozen13
Vitamin E in frozen foods was not really mentioned, so I will skip this portion.
When looking at the minerals sodium, calcium, and potassium, some interesting results were noticed. Across the board, concentrations of potassium and calcium were similar after cooking for fresh, frozen, and canned foods when testing green beans and peas12. One can assume that canned foods will have a higher amount of sodium due to processing12. What this tells us is that generally, produce will have similar amounts of the beneficial minerals. If you’re watching sodium, opt for either non-canned options or those that are sodium-free/no salt added. One caveat, this study only looked at those two vegetables. The results may be different when looking at fruits and vegetables. My personal opinion is that it may not be too different simply because minerals are more resistant to heat and cooking than the vitamins.
In reference to the last post, fiber isn’t really lost from the cooking process unless you physically remove the tough, fibrous, parts of food. Researchers went to the grocery store and purchased some food off the shelf to observe its fiber content and compare fresh, frozen, and canned foods. What they found was that cooked frozen and cooked canned green beans and peas had 25%-35% greater amounts of fiber than the cooked fresh counterpart12.
Keep in mind, this is one grocery trip they took. Fiber content may vary between batches, but it is an interesting point because I think that most people would think that the fresh food will always have more nutrients, which, as we just saw, is not always the case.
Phew, this was a longer post than most of the others. My b. But there was a lot to cover! I will be going over specifically canned produce next week, so look forward to that! Here are my takeaways!
- Frozen foods last significantly longer than fresh foods. If you plan on having food for a long time or like to stockpile for nuclear war for some weird reason, go frozen.
- In many cases, frozen foods have similar nutrient amounts to fresh.
- In addition, frozen foods take a long time on average to lose a lot of their nutrients, so store those babies for a while, you’ll be good!
- Frozen foods (including meals) are a quick and easy way to make a meal, since the prep work is usually done.
- Try limiting the time you heat/cook any kind of produce. The longer it stays in hear or water, the greater chance you will lose nutrients
- On the other hand, don’t drive yourself nuts and only eat raw foods, that’s not the way either. If you can limit water and heat use and still get the same product, great. If not, no biggie, enjoy your damn food.
I hope you found this article useful. Let me know how use frozen foods in your meals/meal planning, I’m always looking for ideas!
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8Rickman, J., Bruhn, C., & Barrett, D. (2007). Nutritional comparison of fresh, frozen, and canned fruits and vegetables II. Vitamin A and carotenoids, vitamin E, minerals and fiber. Journal of the Science of Food and Agriculture, 87(7), 1185-1196.
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