ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Thermal stability, antioxidant activity, and photo-oxidation of natural polyphenols

Irina Volf, Ioana Ignat, Mariana Neamtu, and Valentin I. Popa

Faculty of Chemical Engineering and Environmental Protection, “Gheorghe Asachi” Technical University of Iasi, 73 Prof. dr. docent Dimitrie Mangeron Bd., 700050, Iaşi, Romania

E-mail: mariana.neamtu1@yahoo.de

Abstract: The thermal stability (60°C, 80°C, 100°C), antioxidant activity, and ultraviolet C light (UV-C) stability of standard polyphenols solutions (catechin, gallic acid, and vanillic acid) and of vegetal extracts from spruce bark and grape seeds were investigated. Exposure of the standard solutions and vegetal extracts to high temperatures revealed that phenolic compounds were also relatively stable (degradations ranged from 15 % to 30 % after 4 h of exposure). The highest antioxidant activity was obtained for ascorbic acid and gallic acid followed by catechin and caffeic acid and the grape seeds. The results show that, after 3 h of UV-C exposure, approximately 40 % of vanillic acid, 50 % of gallic acid, and 83 % of catechin were removed. Similar degradation rates were observed for vegetal extracts, with the exception of the degradation of catechin (40 %) from grape seeds. In addition, the photo-oxidation of polyphenols in the presence of food constituents such as citric acid, ascorbic acid, sodium chloride, and sodium nitrate was assessed.

Keywords: polyphenols – photo-oxidation – thermal stability – radical scavenging activity – food additives

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-013-0417-6

Chemical Papers 68 (1) 121–129 (2014)