"We found that dried plums, when pureed, actually have a very good antioxidant capacity," said lead researcher, Professor Jimmy Keeton, from Texas A&M.
Interest is growing in plant-derived food additives as replacements to synthetic antioxidants like butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT) to slow down the oxidative deterioration of food.
Indeed, according to a 2003 report by Frost and Sullivan, the synthetic antioxidant market is in decline, while natural antioxidants, such as herb extracts (particularly rosemary), tocopherols (vitamin E) and ascorbates (vitamin C) are growing, pushed by easier consumer acceptance and legal requirements for market access.
The new research, funded by the California Dried Plum Board, has looked into the effects of dried plums and plum juice in ready-to-eat meat products, like pre-cooked pork sausages, roast beef and ham, said Keeton, to see which of those products will respond most effectively as antioxidants.
"We found that pre-cooked and uncured products like sausages and roast beef actually respond the best," he said.
Typically, the oxidative deterioration of meat and meat products is caused by the degradation reactions of fats and pigments. Oxidation processes in food can lead to organoleptic deterioration in taste, colour and texture.
"If these are unsaturated fatty acids, they can oxidize more and produce off-flavors and cause shelf life problems," explained Keeton.
The use of such natural additives has the extra advantage of the health benefits associated with the extracts. Recent research from Oklahoma reported that the dried fruit has potential as a functional food ingredient since results from a rat study reported a potent effect on bone metabolism and prevention of the deterioration in bone mass (Bone, doi: 10.1016/j.bone.2006.05.024).
The Texas A&M researchers found that dried plum pate worked best with ground meat products like sausages, while dried plum juice was most effective with beef roasts. The next step in the research, said Keeton, was to test the puree with lean meat products.
"Unsaturated fatty acids are found in lean tissue membranes, and therefore it can be a benefit because it prevents the oxidation of them in the membranes," he said.
"Companies will have to look at the market and decide if this ingredient will work for them," said Keeton. "It's not expensive, but it must be listed as an ingredient added to the product."
The ingredient could also enhance the flavour of some products, frankfurters in particular, Keeton said.
"We've actually had consumers tell us they prefer the flavour of products with the dried plum ingredient," he said.
And concerns about laxative effects associated with prunes are unfounded, said Keeton, since the small amounts used should not be a concern to most people.