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Shine a light

Posted 04/05/2011 by KatieJ

Hands up everyone who checks the use-by-date of pre-packed vegetables and fruit in the supermarket and who reaches to the back of the display to find the packs with the longest dates, believing them to be the freshest?

Well, US researchers have discovered that this may not be the best shopping strategy after all. Scientists at the US Department of Agriculture’s Agricultural Research Service (ARS) have discovered that the packs that receive the greatest exposure to light – particularly those at the front of the display in the full glare of the supermarket’s lighting – may in fact be the better choice.

Postharvest plant physiologist Gene Lester and his team at the ARS Crop Quality & Fruit Insects Research Unit in Weslaco, Texas, found that spinach leaves exposed to continuous light during storage were, overall, ‘more nutritionally dense’ than leaves exposed to continuous darkness.

The experiments were conducted under conditions very similar to those found in refrigerated supermarket display cabinets, which are usually maintained at 4oC, with the spinach leaves contained in plastic tubs with snap-on lids that allowed light transmission. One group of samples was exposed to 24-hour fluorescent light, while the second group was placed in two-layer brown paper grocery bags.

The team determined that continuous light affects the photosynthetic system of the leaves, despite being separated from the whole plant, resulting in significant increases in the levels of carotenoids and vitamins C, E, K and B9. The storage period did have some effect on the overall appearance of some samples. Some wilting did occur in flat-leaf spinach after three days’ storage, however, no wilting was observed with crinkled-leaf types.

So that visit to the fresh produce area of the supermarket has just become even more complicated! And when you get them home, those fresh vegetables shouldn’t be left in the dark!

Neil Eisberg - Editor

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