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:
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.)
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)