Antioxidants in heat-processed koji and the production mechanisms

Kayu Okutsu; Yumiko Yoshizaki; Natsumi Ikeda; Tatsuro Kusano; Fumio Hashimoto; Kazunori Takamine

doi:10.1016/j.foodchem.2015.04.004

Antioxidants in heat-processed koji and the production mechanisms

Food Chem. 2015 Nov 15:187:364-9. doi: 10.1016/j.foodchem.2015.04.004. Epub 2015 Apr 18.

Authors

Kayu Okutsu¹, Yumiko Yoshizaki¹, Natsumi Ikeda¹, Tatsuro Kusano¹, Fumio Hashimoto², Kazunori Takamine³

Affiliations

¹ Division of Shochu Fermentation Technology, Education and Research Center for Fermentation Studies, Faculty of Agriculture, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan.
² Department of Horticultural Science, Faculty of Agriculture, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan.
³ Division of Shochu Fermentation Technology, Education and Research Center for Fermentation Studies, Faculty of Agriculture, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan. Electronic address: takamine@chem.agri.kagoshima-u.ac.jp.

PMID: 25977038
DOI: 10.1016/j.foodchem.2015.04.004

Abstract

We previously developed antioxidative heat-processed (HP)-koji via two-step heating (55 °C/2days → 75 °C/3 days) of white-koji. In this study, we isolated antioxidants in HP-koji and investigated their formation mechanisms. The antioxidants were identified to be 5-hydroxymethyl furfural (HMF) and 5-(α-D-glucopyranosyloxymethyl)-2-furfural (GMF) based on nuclear magnetic resonance spectral analysis. HMF and GMF were not present in intact koji, but were formed by heating at 75 °C. As production of these antioxidants was more effective by two-step heating than by constant heating at 55 °C or 75 °C, we presumed that the antioxidant precursors are derived enzymatically at 55°C and that the antioxidants are formed subsequently by thermal reaction at 75 °C. The heating assay of saccharide solutions revealed glucose and isomaltose as HMF and GMF precursors, respectively, and thus the novel finding of GMF formation from isomaltose. Finally, HMF and GMF were effectively formed by two-step heating from glucose and isomaltose present in koji.

Keywords: 5-Hydroxymethyl furfural; Antioxidant activity; Isomaltose; Rice koji.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Antioxidants / analysis*
Aspergillus*
Fermentation
Food Analysis*
Food Handling*
Functional Food
Furaldehyde / analogs & derivatives
Furaldehyde / analysis
Hot Temperature*
Hydrogen-Ion Concentration
Magnetic Resonance Imaging

Substances

Antioxidants
5-hydroxymethylfurfural
Furaldehyde