Dear Food Doc: I enjoy fresh fruits and vegetables, but they take a lot of effort to prepare. Plus, if I don’t eat them right away, they go bad. Are frozen products good alternatives?

Answer: Let’s start with a quiz: How many daily servings of fruits and vegetables are recommended for adults by the Dietary Guidelines for Americans? Would you believe the answer is 7 to 9?

And how many Americans achieve this goal? Yikes, the answer is only 1 in 10. Indeed, one-third of adults consume less than even a single serving of fruits and vegetables.

Thus, fresh, frozen, canned, or dried -- any way to get more fruits and vegetables into our diet is a good thing. It’s certainly hard to beat frozen for convenience and quality.

Many consumers have the perception that frozen vegetables and fruits are more processed and less healthy than fresh. Not only is this not true, studies have shown that frozen versions often contain higher levels of vitamins and other nutrients.

This is because frozen food manufacturers harvest fruits and vegetables at their optimum ripeness when nutritional content is high. In contrast, fresh products are usually picked early to allow for handling and transport. This means vitamins and other nutrients may never reach levels as high as in frozen products.

Plus, in the fresh state, vitamins begin to decay. Studies have shown, for example, that 90% of the vitamin C is lost in green beans after just one week in the fridge.

Worse, fresh produce eventually spoils due to microbes. Moldy grapes and strawberries have a huge yuck factor. Wilting, bruising and over-ripening also lead to discarded foods. Collectively, one-third of all fresh produce goes uneaten every year.

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Not only do frozen products retain vitamins, quality is maintained for weeks or even months. This assumes, however, your freezer works well. Freeze-thaw cycles encourage formation of ice crystals that damage structure and texture.

For sure, fresh is the only way to go for products like lettuce and avocados. Most grocery stores now carry a variety of pre-washed, pre-cut, ready-to-eat produce. So whether frozen or fresh, there is no excuse to not eat your veggies.

Dear Food Doc: I am a family physician. Recently, one of my patients informed me he makes his own yogurt using commercial yogurt as a starter. When he uses skim milk or whole goat milk, it works fine. But it fails when he uses whole homogenized milk. Any idea why?

Answer: While I have no doubt this failure to ferment occurred, there is no obvious explanation. Although low-fat yogurt is the most popular type, it’s easy to find many brands of whole milk yogurt. Most are made from homogenized milk.

Likewise, goat milk, whether skim or whole, should not make a difference.

Based on your account, there appear to be several uncontrolled parts of this experiment. Commercial yogurt is fine as a starter provided it is fresh and the bacteria are active. Maybe fresh starter was used on days when there was successful fermentation, but old starter on the failure day.

Homemade yogurt instructions usually require a heat treatment. If the milk was over-cooked, the culture will not grow well. Likewise, most recipes call for addition of nonfat milk powder. If omitted, the yogurt will be soft and runny.

My suggestion is to advise this gentleman to try again, accounting for the necessary controls. Or perhaps have him take two aspirin and call back in the morning.

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Bob Hutkins is the Food Doc. He is a professor at the University of Nebraska-Lincoln, where he teaches and conducts research in food science and food microbiology. Send your questions on any topic related to food, food safety, food ingredients and food processing to the Food Doc at features@journalstar.com.


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