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Pinot noir grape polyphenolic extracts are potential natural antimicrobials.

Wine grape pomace is an excellent source of phenolic extracts that could be used to improve our oral health. Scientists at Cornell University have fractionated and characterized grape polyphenolic extracts prepared from pomace in an effort to investigate their antimicrobial properties. It appears that phenolic grape extracts composed mainly of flavan-3-ols and flavonols are promising natural antimicrobial agents.

The researchers prepared phenolic extracts from Pinot noir grape pomace or seeds. They chose these because of their high polyphenolic content. Pomace was obtained after the grapes were crushed, fermented on skins, pressed, freeze-dried and ground. Seeds were separated from the pomace, washed, dried and ground. Polyphenols were extracted using methanol, ethanol and water, and then separated by solid-phase extraction to produce powdered main (total) phenolic and whole seed extracts. The extracts were fractionated into anthocyanin, neutral, polymeric and oligomeric fractions.

The scientists analyzed the extracts for total phenolic content--gallic acid equivalent (GAE); monomeric anthocyanin content--malvidin-3-glucoside equivalent (MGE); flavan-3-ol content--catechin equivalent (CE); as well as for their antioxidant capacity--vitamin C equivalent antioxidant capacity (VCEAC); HPLC profile and yield. They determined what effects the powdered extracts would have on the growth of Alicyclobacillus acidoterrestris, a juice spoilage bacteria, using the well diffusion method. They also examined the effects of the extracts on the formation of biofilms of Streptococcus mutans, an oral pathogen.

The total phenolic content of the extracts ranged from 8 g to 62 g GAE per 100 g. The antioxidant capacity was the highest in the polymeric fraction and the lowest in the anthocyanin fraction (85 g VCEAC and 6 g VCEAC per 100 g, respectively). The flavan-3-ol content ranged from 48 g CE per 100 g to 76 g CE per 100 g. The polymeric fraction had the most yield at 4.8 g of extract per 100 g of fresh weight.

All extracts, except the anthocyanin fractions, were effective in inhibiting the growth of A. acidoterrestris at concentrations as low as 1000 ppm, and in reducing the production of biofilms and insoluble polysaccharides--oral plaque--by S. mutans.

Further information. Randy W. Worobo, Department of Food Science and Technology, Cornell University, New York State Agricultural Experiment Station, 630 W. North St., Geneva, NY 14456; phone: 315-787-2279; fax: 315-787-2284; email:
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Publication:Microbial Update International
Date:Aug 1, 2009
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