Fresh, Frozen, or Canned? 10 Things to Know about Produce

In a favorite foodie book that I reviewed here, the author performed "inventories" of people's kitchens. She would root through their cabinets and refrigerators, figuring out what they really ate (or didn't eat, in the case of the refrigerator crisper drawer).

As you might expect, results were quirky, surprising, and largely grim. The author then proceeded to give the embarrassed person basic cooking lessons, and all was well. Or at least improved.

As our stupid 12-year-old refrigerator is on its last legs and has become incontinent during the cooling cycle again (and the ice maker and water dispenser haven't worked in ages), I've been researching its replacement. Farewell, hundreds and hundreds of dollars! But it did occur to me that I could do a vicious purge of the appliance's contents and start fresh.

What contents, you say? Let's say we just talk about the produce, since that's where I'm headed here. A quick scan revealed:

  • Two bunches of scallions. I forgot I still had some and purchased more.
  • Four apples, one Braeburn (icky and mushy from Fred Meyer--I have to use them in smoothies because no one will eat them) and three Cameo from QFC (a little crunchier, but it may be time to give up on apples until the Bellevue Farmers Market has them in the summer).
  • Three D'Anjou pears. Still decent and still local.
  • Half a Napa cabbage head.
  • The ancient core of a head of lettuce, fist size, as if the cartoon witch doctor got a hold of it.
  • Three bunches of celery, two partial and one whole. Note to self: stop buying celery!
  • One broccoli crown.
  • One bunch of carrots.
  • Half a cucumber.
  • One bag grapefruit.
  • One bag mandarin oranges.
  • One bunch bananas.
  • Three heirloom oranges.
  • One box frozen spinach.
  • One bag frozen green beans.
  • One bag frozen peas.
  • One bag frozen corn.
So what I wondered was, which are most nutritious? Fresh or frozen? I would throw canned in there as well, except I hardly ever have canned vegetables or fruit, besides tomatoes.
Remember what picked-that-day looked like?
If you have time, read this entire article from UC Davis on the subject. If you don't, I have boiled it down to 10 Things to Know About Produce:
  1. Fruits and veggies grown in North America may spend up to 5 days in transit before they hit the shelves. Produce grown from farther afield might spend a few days (air freight) to several weeks making the journey.
  2. Nutrient composition is affected by the timeline, mechanical harvesting, temperature, handling, and how the food is prepared.
  3. Water-soluble vitamins like C and B are degraded by processing and leach out into cooking water or the canning medium.
  4. Canning does reduce vitamins C and B content by 10-90% and 7-70%, respectively, but after that the nutrient level stabilizes. (Whew! Wouldn't want to lose that last 10-30% of the nutritional value!)
  5. Even frozen produce is blanched before freezing, with some nutrient loss, but if properly stored afterward, the C and B nutrient levels stabilize. Until you then cook them, I suppose.
  6. Good news! Canned tomatoes have higher lycopene content than fresh exactly because of the heat used in processing them.
  7. Good news, part two! Fiber content remains relatively unaffected by thermal processing or by freezing, so there's that.
  8. Good news, part three! The fat-soluble vitamins like A and E, and the carotenoids (which include lycopene) actually stay pretty stable during storage, processing, and cooking. In fact, for carrots, as they sat a couple weeks in refrigerated storage, their beta carotene levels increased. Not so for green beans.
We hang on to our lycopene, thank you very much.
What does all this mean? Two takeaways:
1. When possible, eat fresh produce that hasn't traveled long or been exposed to heat. Keep your produce cold and eat it soon after buying. When not possible, canned and frozen vegetables and fruits will do, but you probably have to eat more of them to get the same nutritional value. 
2. Those vegetables and fruits we buy at the Bellevue Farmers Market, often harvested that morning or the day before, are at their nutrient peaks. We should buy as we go (Thursday, and again on Saturday) and consume ASAP. What's the point of eating vegetables if they aren't even as good for you as you hoped?