Healthy fruit and veg compounds being lost in processing
epidemiological studies could be much more powerful if processors
and breeders paid closer attention to their preservation, say Dutch
researchers.
A team from Wageningen University that has assessed the damage done to phytochemicals in a variety of differently processed fruit and vegetables for several years has found that almost all stages of the 'farm-to-fork' chain reduce the level of healthy compounds.
Furthermore, processing can affect the amounts of health-promoting compounds in fruit and vegetable products so much that it could account for the variation in findings from studies investigating their health benefits, one of the researchers, Dr Ruud Verkerk, told NutraIngredients.com.
It is already well-known that levels of vitamins decline when fruit and vegetables are processed but Dr Verkerk and colleague Matthijs Dekker have shown similar damage to glucosinolates, phytochemicals that have been shown in the laboratory to fight cancer and may also protect the memory.
Their survey of pre-cut, frozen, ready-to-eat, juiced and canned fruit and vegetables found that the more fruit and vegetables were processed, the lower their levels of glucosilonates.
Chopping was the only process to improve levels of glucosinolates - pre-cut veg stored in ambient conditions for 24 hours showed increased levels of the compounds. Ready-to-eat vegetables also showed 'quite reasonable' levels of the phytochemicals, according to Dr Verkerk.
"Many studies show a correlation between intake of fruit and vegetables and lower incidence of disease. But often the results vary. We think this could be because all types of fruit and vegetables are treated the same, yet they differ a lot in the levels of glucosinolates at least," he said.
Dr Verkerk believes that researchers should include information on the types of fruit and vegetables consumed by a study population when gathering data on intake. This would improve information on the amount of health compounds the subjects are getting.
The Wageningen team also used their experiments to develop mathematical equations for the different parameters that influence glucosinolate levels, such as temperature, time in processing, or even domestic food preparation.
"We could then play with these on our computers to see how you could improve the glucosinolate levels," explained Dr Verkerk.
The simulations predict an approximate 45 per cent reduction in the risk of colon cancer if the entire food production chain can increase the average quality of healthy substances in fruit and vegetable products by three times.
Breeding and cultivation also play a significant role in the variation of healthy substances found in fruit and vegetables, yet Dr Verkerk says breeders and processors do not yet work together to ensure optimum levels of healthy compounds.
This is perhaps due to the lack of consumer awareness and therefore demand for information on particular fruit and vegetable compounds.
"The consumer can see the colour and other quality markers but not the healthy components," noted Dr Verkerk.
Yet increasing media attention on studies showing the health benefits of phytochemicals - protection of heart health and reduced risk of cancer are but a few - may drive demand for this kind of information. And this could offer food producers an area of differentiation.
Dr Verkerk believes that an organisation should take responsibility for communicating the difference in glucosinolate, and other phytochemical levels, to consumers.
"Measuring these compounds is very laborious and expensive. But there is a great deal of interest from industry. Yet the whole food chain must collaborate before producers can market an advantage," he explained.
The Wageningen team's latest research is available in the Journal of Food Chemistry early online edition.
