Abstract:

Abstract Hazelnut skin is a valuable waste as it contains a large amount of polyphenols, which have many health effects, including antioxidant and anticancer properties and the prevention of cardiovascular diseases. In this study, total polyphenol content, antioxidant capacity and in-vitro digestion of polyphenols of the hazelnut skin were investigated. Gallic and ellagic acids, which are important phenolic compounds of hazelnut skin, were determined by HPLC. In addition, the potential use of hazelnut skin extract in noodle production was investigated in order to gain functionality to noodle, which is a widely consumed product. The hazelnut skin contained 49.00 mg gallic acid equivalent/g dry matter total polyphenol and had 62848.57 mmol ascorbic acid equivalent/100g dry matter antioxidant capacity. Gallic acid content (20.39 mg/g dry matter) of hazelnut skin was found to be approximately 5.4 times higher than ellagic acid (3.80 mg/g dry matter). After the gastrointestinal track, the total polyphenol content was lower than the initial value as the antioxidant capacity of the skin extract. The addition of the skin extract (0.4%) to the noodle dough increased the total polyphenol and antioxidant capacity of the final product compared to control. As in the skin extract, it was observed that the stability of the polyphenols from the noodle sample was higher in gastric stage than intestinal one. The addition of hazelnut skin extract to the noodle dough increased the bioaccessibility of the noodle polyphenols. Therefore, this study showed that hazelnut skin, as an important source of polyphenols, may be useful for food enrichment

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