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Packaged spinach stays healthy under daylong light

Photonics Spectra
Apr 2010
Lynn Savage, Features Editor, lynn.savage@photonics.com

Barely seven steps into most supermarkets and you are confronted with a wall of green – rows of packaged lettuce and spinach hoping to lure you toward healthy eating habits. Spinach, in particular, is full of nutrition, but how healthy can it be after being drenched in the glow of whitish-yellow fluorescent light for hours on end?

According to researchers in Texas and Nova Scotia, very healthy indeed.

Fresh spinach, especially the smaller, younger leaves called baby spinach, is one of the most nutritionally dense foods on the market. It is loaded with vitamins C, β9, E and K, as well as carotenoids such as ?arotene. Most of these provide antioxidant functions; all provide healthful benefits.

Once packaged produce reaches the store shelves, though, it typically remains refrigerated for days under artificial light 24/7. The packaging itself is transparent, not counting any labeling, which means that the spinach leaves are left to soak up the multiwavelength radiation. Gene E. Lester and Donald J. Makus of the US Department of Agriculture in Weslaco, Texas, and their colleague, D. Mark Hodges of Agriculture and Agri-Food Canada in Kentville, Nova Scotia, wanted to know what effect the light had on the food.

The group harvested and refrigerated various sizes of two varieties of spinach leaves, then stored the samples in either dark or light conditions for zero to nine days. They then measured the samples’ dry weight, plasticity and nutritional composition. They found that, for the most part, the amount of each of the nutrients remained steady – in some cases, even increased – when exposed to 24-h light. Vitamin C, curiously, increased over the first three days, then gradually reverted to baseline over the next six days.

Unfortunately, as the team reports in the March 10, 2010, Journal of Agricultural and Food Chemistry, wilting began to increase after the third day of light exposure. The scientists also found that the light intensity is greatest for the packaged produce closest to the top of a stack compared with the light struggling to reach the depths of a display. If the spinach isn’t visibly at its peak, it might entice shoppers to move on to the ready-made pizza section of the market.

The group did not address how light levels might affect spinach as it is transported – sometimes for hundreds or thousands of miles – inside dark trucks. Still, its work could result in new ways for growers and grocers to illuminate their products, thus improving, or at least maintaining, the goodness in every bite.


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