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Source antimicrobials from grape polyphenolic extract.

Characterizing grape polyphenolic extracts sourced from pomace is one approach to examining their antimicrobial potential.

Scientists at Cornell University did just that and found that the extracts, composed mainly of flavan-3-ols and flavonols, are promising natural antimicrobial agents that could prevent juice spoilage and oral disease.

The researchers made phenolic extracts from Pinot noir grape pomace or seeds, which are known to have high polyphenolic content. The grapes were crushed, fermented on their skins, pressed, freeze-dried and ground in order to obtain the pomace.

The scientists separated the seeds from the pomace. Then they extracted the polyphenols using methanol, ethanol and water. The materials were separated by solid-phase extraction to produce powdered total phenolic and whole seed extracts. The extracts were fractionated into anthocyanin, neutral, polymeric and oligomeric fractions.

The investigators analyzed the extracts for total phenolic content (gallic acid equivalent--GAE), monomeric anthocyanin content (malvidin-3-glucoside equivalent--MGE) and flavan-3-ol content (catechin equivalent--CE), as well as for their antioxidant capacity (vitamin C equivalent antioxidant capacity--VCEAC) and yield. Then they determined the effects of the powdered extracts on the growth of Alicyclobacillus acidoterrestris, a juice spoilage bacterium, and on formation of the biofilm 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 highest in the polymeric fraction and lowest in the anthocyanin fraction (85 g and 6 g VCEAC per 100 g, respectively). The flavan-3-ol content ranged from 48 g to 76 g CE per 100 g. The polymeric fraction had the most yield: 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 biofilm and insoluble polysaccharide production (oral plaque) by S. mutans.

Further information. Randy W. Worobo, Department of Food Science, Cornell University, 360 Stocking Hall, Ithaca, NY 14853; phone: 607-255-3614; email:

Wine grape pomace is an excellent source of phenolic extracts for potential use in oral health.

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Publication:Emerging Food R&D Report
Date:Nov 1, 2017
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