DEAR DR. BLONZ: What are some safe methods for food preservation? I know that some preservatives are synthetic chemicals, but there are also preservatives in "all natural" foods. Is there a significant health benefit to avoiding all forms of food preservation? -- S.F., Charlotte, North Carolina
DEAR S.F.: A predominantly plant-based diet, limited in processed foods and abundant in whole foods, is the most healthful way to eat for many reasons. Add to this a healthful lifestyle and you nudge the odds further in your favor. That said, there is no significant benefit to avoiding all preservatives; here is some background to provide perspective.
If you only ate farm-fresh foods, you'd have little need for food preservation beyond that supplied by a refrigerator or root cellar, along with a means to cook. Most of us have to rely on food suppliers, manufacturers and processors, all of whom must cope with the reality that the nutrients in food are just as attractive to spoilage microorganisms -- bacteria, molds, fungi and yeast -- as they are to us.
Food preservation is needed when a food must be kept safe for an extended shelf life. Typically, that involves a treatment or process to stave off the breakdown most likely to occur. Many methods rely on the fact that, like us, spoilage microorganisms require water to live, grow and reproduce. Here are some safe, basic methods of preservation:
-- Drying removes water from the food.
-- Freezing inhibits spoilage by changing water into ice crystals that microorganisms cannot use.
-- Salting and sugaring are among the oldest forms of food preservation, and work by drawing water out of the microbial cells.
-- Cold temperatures slow the chemical reactions involved in some types of breakdown.
-- Pasteurization can destroy spoilage organisms as the food is briefly heated to high temperatures.
-- Pickling or fermentation (culturing) leaves the food with a higher acid level, making it an inhospitable environment for many spoilage bacteria.
-- Smoking adds smoke-borne chemicals that can destroy potential spoilage organisms.
-- Canning destroys microorganisms through heating, then putting the food in a sealed container that acts as a barrier to prevent further contamination.
Many preservative substances are based on compounds that successful plants evolved to produce; nature is a great instructor. For example, antioxidants prevent chemical reactions with oxygen (oxidation), which leads to rancidity, "off" flavors and discoloration. Natural antioxidants include tocopherols (vitamin E), which are found in plant seeds to protect the lipids needed to fuel the growth of the next generation. Ascorbate (vitamin C) and carotenoids (vitamin A) keep fruits and vegetables fresh. Fruits such as cranberries, raisins, prunes and citrus contain naturally occurring acids that make effective antimicrobial agents. These compounds include citrates, propionates, benzoates, sorbates and lactates.
As an example, raisin juice is a source of naturally occurring propionic acid, often used in "all-natural" bread to slow down mold formation. The "artificial" alternative is synthesized calcium propionate, where calcium gets combined with propionic acid. Both compounds are harmless at the levels used, and they perform the same function, but sourcing from raisin juice allows the bread manufacturer to make a "natural" assertion.
Finally, this reply is not an unqualified endorsement of preservatives. It should provide some appreciation that there are levels of complexity to this topic. Read more about different types of additives in the downloadable booklet at b.link/z8yadf.
Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.