Frozen spinach retains carotenoid power for longer than fresh
fresh equivalent, say food scientists.
Researchers at Penn State University in the US found that spinach stored at 39 degrees Fahrenheit loses its folate and carotenoid content at a slower rate than spinach stored at 50 and 68 degrees.
But the spinach at 39 degrees still loses much of its nutrients after eight days.
This latest research demonstrates the challenge for food makers to keep the nutrients - notably folate and carotenoids - of spinach "in".
Folate is a vitamin B compound, responsible for producing and maintaining new cells in the body. Carotenoids, used extensively in the food industry as colouring agents and commonly found in yellow, red and green vegetables, are most commonly associated with carrots and other red and orange vegetables, may reduce the risk of degenerative diseases, such as age-related macular degeneration.
They are also linked to a preventative effect on heart disease and certain cancers.
Mostly used as a natural colouring, carotenoids have been 'under-utilised' by Europe's food industry, according to a recent Frost & Sullivan report on the $348.5 million (€291.4m) market, and consumers are still unaware of their health benefits.
The Penn State food scientists underline that "attractive appearance" does not mean that the spinach is still rich in nutrients. According to lead researcher Luke LaBorde, associate professor of food science, and Srilatha Pandrangi, graduate student, spinach stored for a long time loses much of its nutrient content.
"Some people think that if the produce looks good, it has nutrients," says LaBorde, adding that canned or frozen spinach could be the better option.
Despite the damage done during the heating process for canned spinach, it may retain more of its nutrients than fresh spinach kept in the refrigerator for a few days. The same holds true for frozen spinach, add the scientists.
Frozen spinach retains more of its nutrients for a longer time than fresh spinach because of the lower temperatures at which it is kept.
The researchers found that spinach stored in a refrigerator at 39 degrees retained more nutrients than spinach kept at warmer temperatures. While they found that substantial nutrient loss occurred at all storage temperatures, the cooler temperatures retained more nutrients for a longer period of time.
The spinach kept at 39 degrees retained only 53 per cent of its folate after eight days. When it was kept at higher temperatures, the spinach lost its nutrients at an accelerated rate. At 50 degrees it took six days for the spinach to lose 47 per cent of its folate and at 68 degrees it took four days. The same held true for carotenoid loss, report the researchers.
As temperatures increased, they found that the loss of nutrients also occurred at a faster rate.
Full findings for the Penn State study are published in the lastest issue of the Journal of Food Science.
