Have You Ever Wondered

. . . why boxed fluid milk is sold on the grocery shelf, not the dairy case? Aseptic packaging, a relatively new food processing and packaging method in the United States, allows fluid milk to be stored on the shelf at room temperature for up to a year without preservatives. Sterilization is the key to preventing spoilage. Food is first heated quickly (three to fifteen seconds) to ultrahigh temperatures to kill bacteria. Then it's packaged in a sterilized container, such as a box, within a sterile surrounding. This process of flash heating minimizes loss of nutrients, texture, color, and flavor—and extends shelf life. Besides milk, look for many other grocery items sold in aseptic packaging—for example, soup, tofu, liquid eggs, tomatoes, soy beverages, juice and juice drinks, syrup, nondairy creamers, and wine. In the future, you'll find even more!

Today foods are still pasteurized, or perhaps ultrapas-teurized at higher temperatures, to keep food safe and flavorful and extend shelf life. Early-twentieth-century technology launched frozen foods. Later, lightweight, freeze-dried foods were developed for the space program; today backpackers and cyclists use them. Processing makes it easy to have foods, such as olive oil, that may not be grown, harvested, or produced where you live. In reality, most of our food supply is processed for the benefits of consumer safety and food variety.

What are today's newer contributions to food processing? Many relate to health—for example, adding substances for their nutrient benefits or functional qualities . . . using fat replacers and intense sweeteners to cut back on fat and added sugars . . . and irradiating food for improved food safety. And many add flavor, too.

Fresh vs. Processed: Either Way to Health

The flavor of fresh produce in season is hard to beat: freshly picked, handled properly, and eaten right away! For convenience, their canned and frozen counterparts offer another option. Research shows that canned and frozen ingredients are comparable in nutrition to cooked fresh counterparts.

The moment you pick a fruit or a vegetable, or catch a fish, or milk a cow, food starts to change texture, taste, perhaps color, and nutrient content. That's why food producers usually process food as fast as possible, while nutrient content and overall quality are at their peak. Immediate processing helps lock these qualities into food. In canneries on board some fishing vessels, seafood is processed as it's brought in. Tomatoes are canned just yards away from the fields. The same is true for commercially frozen foods.

As long as processed foods are handled properly— from the food manufacturer to the supermarket to your home—there's little nutrient loss. Freezing, drying, and canning retain the nutritional quality of foods.

A processing method called fortification increases the nutritional value of food by adding nutrients, such as vitamins or minerals, not present naturally or replacing nutrients removed. Milk, for example, is fortified with vitamin D, which helps the body handle calcium for bone-building; grain products are fortified with folic acid to reduce risk for birth detects. The nutritional quality of fresh fruit and vegetables depends on their care after harvest. Handled or cooked improperly or stored too long, they may not be quite as nutritious as their canned or frozen counterparts.

Whether food is fresh or processed, it's up to you to minimize nutrient loss in your kitchen. Store, prepare, and handle all foods with care. See "Food'Prep': The Nutrition-Flavor Connection " in chapter 13.

Irradiated Foods: Safe to Eat?

Like canning and freezing, irradiation is a food processing method that enhances an already safe food supply. It extends the freshness of food, helping to retain its quality and safety longer.

Since it uses no heat, yet destroys disease-causing bacteria, irradiation is sometimes called "cold pasteurization." Poultry and beef can be irradiated to ensure pathogens that are especially harmful to children, the elderly, and people with weak immune systems are destroyed. That includes Escherichia coli O157:H7, Salmonella, and Campylobacter. Irradiation also slows ripening and retards sprouting—for example, in potatoes.

Irradiation destroys bacteria, mold, fungi, and insects by passing food through a field of radiant energy, much like sunlight passes through a window or like microwaves pass through food. It leaves no residue. A small number of new compounds are formed when food is irradiated, just as new compounds are formed when food is exposed to heat. These changes are the same as those caused by cooking, steaming, roasting, pasteurization, freezing, and other food preparation.

Irradiated foods generally retain their nutrient value. Like freezing, canning, drying, and pasteurization, irradiation results in minimal nutrient loss. The amount lost is often too insignificant to measure. Irradiation can't take the place of good food handling practices—nor improve the quality of food. As a consumer, you still need to store, prepare, and cook food in clean, safe ways to avoid foodborne illness.

Besides food safety, what are some other advantages of irradiation? Agricultural losses caused by insects, parasites, or spoilage can be cut dramatically. Foods that stay fresh longer can mean less food waste in your kitchen. Like other processing methods, irradiation is regulated and approved by the U.S. Food and Drug Administration (FDA).

By law, whole foods that have been irradiated must be labeled on the package. Look for the international Radura symbol (to the right) and the phrase "Treated by Irradiation" or "Treated with Radiation." Irradiated ingredients in prepared, deli, or restaurant foods usually aren't labeled.

As a way to control foodborne illness, irradiation— studied for safety by the FDA for forty years—was approved in 1997 by the FDA for fresh and frozen meats, including beef, pork, lamb, and poultry. The process protects these foods from contamination by Escherichia coli O157:H7 and Salmonella, but doesn't compromise the nutritional quality of meat. For more aboutfoodborne illness, see chapter 12. Irradiation also is used for vegetables, fruit, wheat flour, and spices. Research continues to evaluate irradiation as part of the overall system of ensuring food safety.

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