7th INTERNATIONAL CONFERENCE ON AGRICULTURE, ANIMAL SCIENCES AND RURAL DEVELOPMENT, Muş, Turkey, 18 - 19 September 2021, pp.596-611
During chestnut processing, a large amount of peels is generated. Chestnut peel is a valuable agricultural waste owing to its high content of polyphenols, which are thought to be responsible for many of the health benefits, including antioxidant, anticancer and prevention of cardiovascular diseases. The bioaccessibility of polyphenols is important to evaluate their stability and absorption in the gastrointestinal digestion. In this study, in vitro digestion of polyphenols from three different chestnut varieties (Sarıaşı, Düzce and Kiraz) was studied. Also, potential use of the peel extract in cracker production was investigated because little is known about valorization of chestnut peel. Stimulated gastrointestinal digestion was carried out as gastric and intestinal stages. Total polyphenol, flavonoid and antioxidant capacity contents of peel and cracker extracts were determined by spectrophotometrically.
The results showed that the stability of polyphenols from chestnut peels and antioxidant capacity varied depending on the variety and in vitro digestion stage. Kiraz variety had the highest content of polyphenol (144.18 mg gallic acid equivalent/g dry matter-DM), flavonoid (195.22 mg rutin equivalent/g DM) and antioxidant capacity (116652.36 mmol ascorbic acid equivalent/100g DM) followed by Sarıaşı and Düzce, respectively. However, in terms of bioaccesibility of polyphenols, Düzce variety was the one with the highest recovery values (20.31% for gastric stage and 16.47% for intestinal stage) after in vitro digestion compared to other varieties. Regardless of the variety, the amounts of polyphenols from peels after each digestion stage were lower in comparison to the amounts before digestion. Similar trend was observed for antioxidant capacity of peel extracts. For all three varieties, polyphenols were more stable under stomach-mimicking conditions than small intestine ones.
Addition of the peel extract (0.4 %) from Kiraz variety to the cracker dough increased polyphenol and flavonoid contents of final product and its antioxidant capacity in comparison with the control cracker (without the addition of the peel extract). As in peel extracts, stability of polyphenols from cracker samples was higher in gastric stage than intestinal one. The chestnut peels might be an important source of polyphenols from suitable chestnut variety, which have great potential in industrial applications as food additives/ingredients.
Key words: Chestnut, polyphenol, in-vitro digestion, cracker