Welcome to all the new readers who found me through my guest post on Carrots ‘n Cake today!
For those of you who are new to Savvy Eats, I am a soon-to-be-graduate studying Food Science and Engineering. I write a series called ‘Just Eat It: Brain Food 101,’ where I answer reader questions about the science behind food.
Some of my favorite posts from the series so far are:
Replacing eggs with flax “eggs”
Today, I’m adding one to the series, with…
Frozen v. “Fresh” Produce
Let’s start with a little quiz, shall we? Don’t worry, it is painless. I took an exam on this material today, but I promise I won’t make you write an essay about it like I did! I’ll write the essay for you. 
Question: Rank the following in terms of likely nutritional quality and content.
A. Fresh sweet peas from the grocery store
B. Fresh sweet peas from a Farmer’s Market
C. Frozen sweet peas
If you chose B > C > A, you would be right!
Wait, the frozen peas have more nutrients than the ones in the produce section at your grocery store? That’s right, folks! (Unless your grocery store specifically states that it sources produce from local farmers, that is.)
Here’s why:
Respiration is the process by which plants turn nutrients into energy so that they can continue to grow and thrive. Fruits and vegetables continue to respire even after they are harvested, but since they can no longer get their fuel from the plant and soil, they must use what they have inside. Plants need fuel too!
Because of this, fruits and vegetables start to convert their nutrients into energy within hours of harvesting, meaning there are fewer nutrients left when we eat them. Unfortunately, they continue to respire throughout the time it takes to make the journey to your grocery store from around the globe. Yes, producers can take some steps to slow down the respiration process, like shipping the fruits and vegetables in dark, refrigerated containers. However, they will still lose nutrients.
Most frozen vegetables and fruits, on the other hand, are frozen within hours of being harvested. The low temperature nearly halts the respiration process, so very few nutrients are lost once they are frozen. One study shows that frozen peas, for example, have 60% more carotene than ‘fresh’ peas from the grocery store! That is a HUGE difference!
Question: Why do the vegetables at your local Farmer’s Market probably have more nutrients than the ‘fresh’ ones at the grocery store?
You can probably guess the answer by now! The fruits and vegetables at your local Farmer’s Market will have less time between harvest and purchase, so won’t have a chance to lose many nutrients. The sooner you eat freshly picked produce, the better!
And when you bring it home, it is a good idea to refrigerate most produce right away. Refrigeration slows respiration and therefore nutrient loss, though not as effectively as freezing does.
(Side note: There are some exceptions to the ‘refrigerate upon purchase’ rule. Bananas will actually brown more quickly when refrigerated, for example.)
Now granted, some methods for reheating and cooking the frozen fruits and vegetables will cause some of the nutrients to be lost. But that will be another Brain Food 101 post for another time!
Check back tomorrow for the Top 5 Reasons to Buy Local Produce!
Edited to add: Sources: On Food and Cooking: The Science and Lore of the Kitchen (Harold McGee), Fennema’s Food Chemistry, Fourth Edition (Food Science and Technology)
{ 11 comments… read them below or add one }
Very interesting!
Your blog is great – just found you recently
Thank you! I’ll have to check out your’s
Julie – CONGRATS on the guest post at Carrots ‘n’ Cake! I loved it and it’s HUGE that you scored the opportunity with Tina, that rocks!
I love this post, too… it totally makes sense as farmer’s market produce always tastes so much better and fresher than grocery store goods do. I have been on the fence lately about buying frozen produce items (versus fresh, at the grocery store), and your post has helped me to prioritize their nutritional values.
Thanks!
I know, I used to be a bit hesitant about frozen produce because I didn’t know if it would be as good, but it is good to know that it is just as (or more) nutritious as fresh!
Cool! Thanks for the info. Now I know the science behind why I wait for most things to be “in season” (ie at my farmers market). I love learning new things – thanks.
great post julie!! and yay for oyur guest post
i just checked it out and it was greatt
love buying local as much as I can. We have a weekly farmer’s market near my work that supplies the casinos with produce too
yay for your guest post!!! love the new look, I’m a big fan of thesis.
I’m not new, but I will have to check out your guest post!
This post was so interesting! I still love my farmer’s market, though! Good thing I refrigerate my produce, too!
Great post! I have a similar one on my blog.
Did you find any good sources on how long between the harvest and the freezing of vegetables? Based on the numbers of a study it looked like the frozen veggies also got shipped around first.
It also depends on the vegetable and on the nutrient. Vitamin C for example is sometimes even lower in frozen produce than in “fresh but not local”. The vegetables still respire a little bit even when in the freezer, so it also depend how old the frozen product is (don’t keep it in there for months…) Also, a lot of times veggies are blanched before they get frozen, and that causes some nutrient loss as well….
Good questions! I think the time between harvest and freezing depends on the brand. I believe Green Giant and Birds’ Eye try to do it the same day the veggies are harvested. The frozen veggies are shipped around, but respiration is much, MUCH slower in frozen v. fresh veggies, so they don’t lose even close to the number of vitamins.
Different vegetables are blanched in different ways to minimize nutrient loss. For example, corn may be blanched using steam, but cabbage is not because it would lose all of its vitamin C. You are right, though, some vitamins are lose during blanching.
I think we all need to eat a variety of fruits and vegetables, and that we can eat a mix of frozen and fresh if we are not lucky enough to live in an area that has great local produce year-round.
Sorry I did not make myself clear. I did not mean veggies get shipped when they are already frozen.
But they get shipped before they are frozen, because the place of harvest and freezing plant is not at the same place. I guess you are right, it really depends on the brand. If they do it at the same day that is great. How long do you think other veggies get shipped around before they end up on the shelves? Any sources on that?
I agree with you, there are advantages and disadvantages in both frozen and “fresh non-local” foods, so a switching it up is a good idea. That was pretty much my conclusion on my blog too. But I have to say, most frozen veggies taste like c&$p. hahaha