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Saturday
May132017

What's Better: Canned Food or Frozen Food?

Processing fruits and vegetables wastes less food but uses more energy than using them fresh. It turns out that frozen food takes a lot more energy than canned food. The nutrition depends on a number of factors, including harvesting, processing, storage method, and age, as this study from UC Davis shows.

As the chart below shows, growing a pound of corn kernels takes about 450 calories. (The corn itself contains just 375 calories, so it takes 120 calories of energy to produce 100 calories of corn.) Canning it takes a total of 2031 calories, largely from the energy needed to make the can. Frozen corn takes less packaging but more processing, with 2985 calories needed for a pound of corn, nearly 8 times the energy contained in the corn itself. (Source: Food, Energy, and Society, third edition, by David Pimentel and Marcia H. Pimentel.)

Chart - energy to process fresh corn, canned corn, and frozen corn

Should You Buy Frozen, Canned, or Fresh Vegetables and Fruit?

Buy fresh, local produce in season whenever you possible. If food has to travel a long way or is out of season, consider canned food first and then frozen food. You'll waste less food while still getting good nutrition. Canned tomatoes and beans have good texture and flavor. Frozen greens are a great convenience and work well in sauces and stews. Experiment to find out what works best for your family.

Reader Comments (3)

What about the BPA (or BPS) in all canned food? Even the "BPA free" cans are lined with a different bisphenol replacement chemical (like BPS), and some of those are even worse than BPA. The can liner is likely releasing an unwanted chemical load into the food, even when the food inside the can is organic. That really worries me.

Dr. Gregor has an excellent, short video about this up at NutritionFacts.org:
https://nutritionfacts.org/video/are-the-bpa-free-alternatives-safe/
(He qualifies as a Very Trusted Source: an evidence-based MD who reviews the peer-reviewed scientific literature.)

His takeaway is to eat fresh or frozen. Maybe the alternative would be for people to home-can and home-freeze fresh, seasonal produce. Home-freezing would cut out the nearly all the processing footprint, wouldn't it?

May 19, 2017 | Registered Commentermagwart

Here's another Dr. Gregor video about fascinating research linking BPA levels and obesity:
https://nutritionfacts.org/video/how-to-avoid-the-obesity-related-plastic-chemical-bpa/

May 19, 2017 | Registered Commentermagwart

Dear Magwart, thanks for raising the excellent points about BPA and other toxins in can liners. This post focused on the energy involved, but that's not the only consideration. As for the energy involved in home canning and home freezing, it depends on the situation. If you already have a freezer and just start keeping food you are freezing yourself instead of frozen pizzas and tater tots, then it would be a win. If you go out and buy a chest freezer or pressure canner and don't make good use of them, then it's probably less efficient from an energy and resource point of view than some factory canning. Sharing with neighbors, family, and friends can help make better use of the equipment. My dehydrator pretty much lives at a neighbor's house because she has a giant garden.

Jun 5, 2017 | Registered CommenterLinda Watson
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