nutrition | July 25, 2017 | Author: Naturopath
While shopping at the supermarket the other day I ran into a friend and noticed that she had a bag of frozen broccoli in her trolley. In response to my question about her preference of frozen over fresh (I could clearly spot beautiful in-season broccoli at the fresh fruit and veg section), my friend explained that she read somewhere that frozen vegetables were more nutritious than fresh ones. Is that really the case? Here is what the research says:
Freezing is one of the oldest forms of food preservation technology in the world, allowing for a significantly extended shelf life. The process of freezing vegetables involves pre-treatments, including:
Preparation - Washing, peeling, slicing or dicing.
Blanching - All vegetables (except herbs and green peppers) need to be blanched prior to freezing. Vegetables contain enzymes that continue to activate even while being frozen, and can cause loss in quality, flavour, colour, texture, and nutrients. Blanching is the exposure of the vegetables to boiling water or steam for a brief period of time in order to inactivate these enzymes, and then rapidly cooling them in ice water to prevent them from cooking.
Canning is another food preservation method; it involves packing blanched vegetables in an airtight sealed container, usually made of tin-coated steel, and then applying heat to the sealed container in order to destroy remaining microorganisms such as bacteria, moulds and yeast. The vegetable may be canned whole, diced, puréed, or as juice.
Generally, the nutritional value of vegetables begins to decline immediately after harvest, so in fact, freezing and canning may preserve nutrient value better than fresh vegetables as they lock in the nutrients soon after they are picked. Fresh vegetables, unless you pick them straight from your backyard or from the local farmers market, may travel great distances before they get to your supermarket.
Nevertheless, the blanching and heating of vegetables in the freezing and canning process may result in some nutrient depletion. Studies found content of vitamin C and of some forms of B vitamins in fresh produce to be higher than in canned and frozen produce. Additionally, many canned foods have added salt, primarily to enhance palatability. Look for no salt added, low sodium or reduced sodium labelled cans.
The Food and Agriculture Organization of the United Nations suggests that freezing is superior to canning with respect to retention of nutrients. Other research reveals that this is not always true, and that canned vegetables are similar to fresh and frozen in terms of nutritional value.
Regarding consumption of canned vegetables, concerns have been raised about the use of the chemical Bisphenol A, or BPA, in the lining of cans. This chemical has been shown to leach into food and is linked to many health problems, including early puberty, infertility, breast and prostate cancer and polycystic ovary syndrome. Food Standards Australia New Zealand (FSNAZ), along with the US Food and Drug Administration (FDA), maintain that BPA is safe at the low levels people are exposed to. Research, however, is ongoing.
Storage and shelf life. Canned foods have a long shelf life, sometimes up to two years, even at room temperature. They do not require refrigerating during transport and storage, and are easy to store even if space is limited. Both canned and frozen vegetables have a longer shelf life than fresh vegetables, thus reducing wastage and frequency of shopping. However, frozen varieties require freezer space that is not always available.
Cost. Canned varieties are more cost saving, as they are cheaper than frozen and fresh vegetables. The cost of fresh vegetables varies greatly, depending on seasonal availability.
Recycling. Steel cans are 100% recyclable, and according to Jamestrong Packaging Australia & New Zealand, Australia ranks 12th in the world for the percentage of steel cans that are recycled rather than sent to landfill. Conversly, most frozen vegetables are packed in plastic bags that cannot be recycled through your home recycling bin.
Eating plenty of fruits and vegetables is a foundation of good health. Freshly picked, unprocessed local produce is best for taste and quality. But if unavailable, inconvenient, or beyond your budget, frozen vegetables are the next best thing. Canned vegetables provide another alternative, but watch the sodium content and limit exposure to BPA.
Barbosa-Cánovas, G. V, Altunakar, B. & Mejia-Lorio, D.J., 2005. Freezing of fruits and vegetables, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 2005. Available at: ftp://ftp.fao.org/
Food Standards Australia New Zealand, 2015. Bisphenol A (BPA). FSANZ. Available at: http://www.foodstandards.gov.au/
Harvard Medical School, 2014, Fresh or frozen produce? The health benefit is all in the mix - Harvard Health. Available at: http://www.health.harvard.edu/
JAMESTRONG PACKAGING - & AUSTRALIA & NEW ZEALAND, CAN - Can and Aerosol News - Education. Available at: http://www.can-news.com.au/
Konieczna, A., Rutkowska, A. & Rachoń, D., 2015. Health risk of exposure to Bisphenol A (BPA). Roczniki Panstwowego Zakladu Higieny, 66(1), pp.5–11.
Miller, S.R. & Knudson, W.A., 2014. Nutrition and Cost Comparisons of Select Canned, Frozen, and Fresh Fruits and Vegetables. American Journal of Lifestyle Medicine, 8(6), pp.430–437.
Rickman, J.C., Barrett, D.M. & Bruhn, C.M., 2007. Review Nutritional comparison of fresh, frozen and canned fruits and vegetables. Part 1. Vitamins C and B and phenolic compounds. Journal of the Science of Food and Agriculture J Sci Food Agric, 87, pp.930–944.