Abstract
Wine pomace has attracted the attention of the food industry, due to its high content in bioactive compounds, and its multiple healthy activities. In this work, whole and separated skin pomaces from fermented (red) and un-fermented (white) grape by-products were characterized for their antioxidant and antimicrobial activities in order to exploit them as functional food ingredient. Antioxidant activity, measured by both ORAC and TEAC assays, was higher in whole than in skin pomace extracts. The characterization of phenolic composition in whole and skin pomace extracts confirmed the peculiarity of some compounds such as anthocyanins (107.84 + 10.3 mg/g TP) in red skin pomace and a great amount of flavanols (80.73 + 4.04 mg/g TP) in white skin pomace. Whole and skin pomace extracts displayed the same antibacterial activity at 250 µg gallic acid equivalents (GAE)/mL. Red and white skin pomace extracts showed a Minimum Inhibitory Concentration (MIC) of 31.25–62.5 GAE/mL against Staphylococcus aureus and Enterococcus faecalis. Pseudomonas spp. were more sensitive to red skin pomace extracts rather than white skin pomace extracts. Given these results, both red and white pomace extracts could be exploited for future application in food, pharmaceutical and cosmetic industry.
Highlights
The health-promoting activities of plant polyphenols have been widely ascertained by hundreds scientific publications
The bioactivities of grape pomace extracts are the result of their polyphenolic profile that is affected by the grape variety, the geographical origin and the winemaking process [1,8,9]
Total phenol content in whole pomace extracts was higher than that found in skin pomace extracts (Table 1)
Summary
The health-promoting activities of plant polyphenols have been widely ascertained by hundreds scientific publications. Grape pomace polyphenols are endowed of antiallergenic, anti-inflammatory, anticancer, anti-ageing, antimicrobial, antioxidant, antithrombotic, insulinotropic, antilipotropic, cardioprotective and vasodilatory activity [7]. Several innovative extraction methods for the recovery of polyphenols with antioxidant, antimicrobial and other biological properties from different grape pomace extracts have been recently explored [7,10,11]. As far as their antioxidant activity is concerned, Gerardi et al [10] found that ultrasound- and microwaveassisted extraction of pomace skin (Negramaro and Primitivo cultivars) using acidified water allowed the highest Trolox equivalents antioxidant capacity values. Feteasca Neagra and Pinot noir grape pomace ethanolic extracts significantly reduced the in vitro inflammationinduced oxidative stress in a concentration dependent way as well as the proliferation of four malignant cell lines [13]
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