Grape extract - a future tool for extending shelf life?
preserving foods, Turkish researchers believe they may have found
one solution in grape extract, which is said to provide an
excellent antimicrobial agent for a variety of processed foods.
The agent, made from grape pomace extract - grape seeds, skin and stems - gave effective anti-bacterial results when tested on all bacteria species at a concentration of five per cent.
"The extracts can be used in food formulations to protect food against spoilage bacteria. People prefer natural preservatives in place of synthetic counterparts in food," said lead researcher Dr Osman Sagdic at Erciyes University.
Anti-microbials prevent the growth of moulds, yeasts and bacteria in processed food. As food production has increased dramatically over recent decades, the growth of food preservatives to keep the products fresh and flavoursome has increased in parallel.
The basic idea behind all forms of food preservation is either to slow down the activity of disease-causing bacteria or to kill the bacteria altogether. There are three classes of chemical preservatives commonly used in foods: benzoates (such as sodium benzoate), nitrites (such as sodium nitrite) and sulphites (such as sulphur dioxide).
But the natural food preservatives market is gaining in pace as consumers turn towards product freshness through natural, not synthetic agents.
"At 5 to 10 per cent depending on the ingredient, the growth rate for natural food preservatives is much higher than the 3 to 4 per cent rate for the European food preservatives market as a whole," Kathy Brownlie, food analyst at market research firm Frost & Sullian tells FoodNavigator.com.
The firm estimates that the value of the European food preservative market, including anti-microbial agents - to be in the region of Euros 72m-81m. By revenue, natural sources make up just 10 per cent of the market, with tonnage considerably less due to he higher prices for the natural ingredients. "In some cases they can be up to 10 times more expensive than synthetic preservatives," added Brownlie.
The Turkish study - published in the August issue of the Journal of Science of Food and Agriculture - set out to determine the total phenolic contents and antibacterial effects of grape pomace extracts (cultivars Emir and Kalecik karasi) against 14 bacteria, and the effects of the extracts on the growth and survival of two of the bacteria during storage.
"All the bacteria tested were inhibited by extract concentrations of 2.5, 5, 10 and 20 per cent, except for Y enterocolitica which was not inhibited by the 2.5 per cent concentration," report the scientists.
But low concentration levels proved ineffective. "Pomace extracts at 1 per cent concentration had no antibacterial activity against some of the bacteria."
The next step for the scientists is find the right food applications to apply the new technology. "What we need to do now is to find a suitable food to put it in. The appearance and taste of the final product must be acceptable to the consumers," said Dr Yiu-Wai Chu, biotechnology group, Society of Chemical Industry.
In addition to being able to destroy food pathogens pomace is also a rich source of polyphenols. Phenolic substances are believed to reduce the risk of heart disease and cancer by inhibiting human low-density lipoproteins. Pomace is already used as an important by-product of winemaking in the production of foods such as vinegar and molasses.
Should the pomace reach the marketplace, the product will compete with other natural food preservatives such as sugar, honey, alcohol, antioxidants and glycerine all targeting this growing market that looks to cater for consumers concerned about product freshness and the use of synthetic chemicals in their food.
