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Extraction of total phenols from grape pomace using novel extraction techniques

Fruits are rich in several bioactive compounds and as such represent the simplest form of functional foods. Some of the bioactive compounds found in fruits showed to have great impact on human's enhancing human health and preventing disease. One of the more important bioactive compounds with impact on human health are polyphenols. Processing of fruits into fruit products result with high amounts of by-product material rich in polyphenols. One of such by-product is the residue of pressed grapes, grape pomace. The extraction of polyphenol from grape pomace has been well studied and numerous methods for polyphenolic extraction are developed. However, there are new extraction techniques which give better yields and higher stability of polyphenols during extraction. The aim of this work was to investigate the effect of cold plasma and ultrasound on the extraction of polyphenolic compounds from dried grape pomace. Cold atmospheric plasma assisted extraction was conducted by using aqueous solution of ethanol or methanol acidified with hydrochloric acid (49.5:49.5:1) and the influence of frequency and treating time were tested. Ultrasound extraction was conducted by using the same solvents, however in this case the influence of temperature and treating time were tested. Total polyphenols were determined by Folin- Ciocalteu spectrophotometric method. The highest yield of polyphenols (30.2 mg/100g) was achieved using aqueous solution of ethanol at frequency 100 Hz, and treating time, 15 min. Considering ultrasound the highest yield of polyphenols (6.0 mg/100g) was achieved using aqueous solution of ethanol at 80 °C, and treating time, 15 min. Antioxidant activity (AOA) of samples was determined by DPPH method. The highest AOA (1.28 moltrolox/ml) was measured in grape pomace extracts obtained by using aqueous solution of ethanol at frequency 100 Hz, and treating time, 15 min. In samples treated with ultrasound, the highest AOA (0.89 moltrolox/ml) was achieved using aqueous solution of ethanol at 80 °C, and treating time, 15 min.

cold plasma, ultrasound, grape pomace, polyphenols, antioxidant activity

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