Adding the phenolic-rich grape-seed extract at a concentration of 0.02 per cent reduced the formation of off-odours associated with lipid oxidation in processed meat without affecting the colour of the product, says the research published in the Journal of Food Science .
The extract, a by-product of fermentation, could be a natural alternative to artificial additives, such as like butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT), said the researchers from the University of Illinois.
According to a 2003 report by Frost and Sullivan, the synthetic antioxidant market is in decline, while natural antioxidants, such as herb extracts, tocopherols (vitamin E) and ascorbates (vitamin C) are growing, pushed by consumer desire acceptance and easier market access.
Martha Rojas and Susan Brewer formulated cooked beef and pork patties containing grape seed extract (0.01 and 0.02 per cent), oleoresin rosemary (0.02 per cent, HerbaLox, Kalsec) and water-soluble oregano extract (0.02 per cent, Origanox, RAD Natural Technologies).
The grape seed extract (Gravinol Super) was provided by Kikkoman who also financed the study.
The antioxidants were mixed with salt (two per cent).
Over eight days of storage, the researchers measured levels of lipid peroxidation, which is associated with the formation of off-flavours in the product.
Using the thiobarbituric acid reactive substances (TBARS) assay they report increases for all of the samples, with the grape-seed extract-containing meat having the lowest TBARS value, and therefore least amount of lipid peroxidation.
Specifically, comparing respective TBARS values to day zero value, Rojas and Brewer report an increase in TBARS for the control samples after six days of storage (64 per cent), while oleoresin rosemary-containing samples had a 59 per cent increase in TBARS after only four days.
On the other hand, the grape-seed extract-containing meats only showed TBARS increases on day eight (69 per cent).
Ten tasters were recruited to assess the sensory quality of the products.
Addition of the grape-seed extract did not change colour measures of redness, yellowness, or colour intensity.
Also, the grape-seed extract-containing beef patties appeared to have a reduced visual green discoloration, report the researchers.
"The higher concentration of grape-seed extract yielded better results than we see with synthetics, which is certainly not what you'd expect.
Synthetics, after all, have been engineered to maximize effectiveness, but sometimes Mother Nature comes up with a better product," said Brewer.
Moreover, the grape-seed extract did not affect the sensory profile of the meat, while foods containing oregano and rosemary retained an herbal odour.
"They must be carrying some of the volatile aroma compounds at low levels," the researcher said.
The researchers confirmed that studies are ongoing, with the focus now on the efficacy and sensory qualities of natural versus synthetic antioxidants.
"I really think grape-seed extract is a viable, natural way to preserve meat quality in the precooked entrees that are so popular now," she said.
"And, when companies can use the word natural on a label, it's attractive to consumers."
Source: Journal of Food Science Volume 72, Issue 4, Pages S282-S288, doi:10.1111/j.1750-3841.2007.00335.x "Effect of Natural Antioxidants on Oxidative Stability of Cooked, Refrigerated Beef and Pork" Authors: M.C. Rojas, M.S Brewer