Alterations in Polyphenol and Inulin Contents of Roasted Jerusalem Artichoke (Helianthus tuberosus L.)

Abstract

Total polyphenol content of roasted Jerusalem artichoke (Helianthus tuberosus L.) increased significantly with increasing temperature and time. Maximum content at 190°C for 30 min was about 7 times higher than that of the non-heated control. Further, DPPH radical-scavenging and α-glucosidase inhibitory activities also increased, and were correlated with total polyphenol content. While caffeoylquinic acids decreased with the increase in roasting temperature and time, a novel component was produced and increased. These findings suggest that the produced component exhibited high anti-oxidative and α-glucosidase inhibitory activities. There was no significant change in inulin content until 170°C for 30 min. Hot water extracts, representing a tea-like drink, contained polyphenol and inulin with high extraction efficiency. Roasted Jerusalem artichoke can be used for tea- or coffee-like drinks and as an ingredient of cakes, breads, noodles, etc. Also, it is expected to exert an antidiabetic effect because of the high inulin and elevated polyphenol contents as well as the α-glucosidase inhibitory and anti-oxidative activities.