Protein precipitating capacity and antioxidant activity of Turkish Tombul hazelnut phenolic extract and its fractions

Natural (raw) hazelnut was extracted with 80% (v/v) acetone to obtain crude phenolic extract that was then fractionated for elution of low-molecular weight (LMW) and high-molecular weight (HMW) fractions. LMW fraction was further purified (LWM-FP) to remove sugars and organic acids. The crude extract and its fractions were determined by measuring their protein precipitating capacity (PPC) using two different proteins [bovine serum albumin (BSA) and gelatin], molecular weights, total phenolics, condensed tannins, and various antioxidant activities. Significant differences (p<0.05) existed in the contents of total phenolics, condensed tannins, antioxidant activities, and PPC among the crude extract and fractions, albeit to different extends. BSA and gelatin was effectively precipitated by HMW fraction. HMW fraction had the highest total phenolics, condensed tannins, and antioxidant activities, followed by crude extract, LWM-FP, and LMW, respectively. The present study suggests that HMW fraction could be utilised as a source of polyphenols for the food industry.