Author
Sae Ueda, Yutaka Inoue, Laboratory of Nutri-Pharmacotherapeutics Management, Faculty of Pharmacy and Pharmaceutical Sciences, Josai University
Keywords
ATR-FT-IR, Principal component analysis, Carbohydrate, Amino acid, Antioxidant
Abstract
We characterized the carbohydrate and amino acid content of Japanese rice wine, the antioxidant capacity in rice wine, 1H-NMR measurements, and principal component analysis (PCA) using ATR-FT-IR spectra. Three samples were tested. The glucose, allose, and raffinose contents in samples (A, B, C) in g/100 g were: (3.47, 3.45, 7.05), (1.60, 1.63, 1.61), and (2.14, 2.75, 1.49), respectively. Total amino acids were 3.1, 3.5, and 4.4 μmol/mL, respectively. The content of glutamic acid, alanine, and arginine was different in each sample. The 1H-NMR spectrum showed signals around 1 ppm derived from branched-chain amino acids and around 3-5 ppm derived from carbohydrates, amino acids, and organic acids. Especially around 7-8 ppm, different signals at ppm were: (8.03, 8.06, 8.51), (7.73, 7.95, 8.06, 8.51) and (7.73, 7.83, 8.51). The IC50 values from DPPH radical scavenging test for antioxidant evaluation were (2364.7±185.3, 3041.9±355.1, and 3842.7±228.1) μg/mL. PCA using FT-IR spectra separated the scores by the PC2 and PC3. In the loading plot, PC2 showed peaks at: (-OH group; 3363 cm-1 and -CH group; 3203 cm-1), and the PC3 were observed peaks at: (-CH group; 2973 and 2887 cm-1, C=O; 1739 and 1720 cm-1, and C-O-C; 1151, 1086, 1040, 937, 879 cm-1). Consequently, PCA using IR spectra proved to be a useful method for characterizing the three Japanese rice wines.