Evaluation of the state of water at different aging stages of filtered soy sauce by a new method using infrared/far-infrared spectra in the 4 000–100 cm^-1 region

抄録

This study evaluated the state of water in filtered soy sauce produced using whole and defatted soybeans at different aging stages through a novel spectroscopic approach using spectra in the 4 000–100 cm^-1 region. Two indices, A_{3 210}/(A_{3 210}+A_{3 374}) and A₆₇₃/(A₆₇₃+A₄₀₃), were developed using absorbance at 3 210 and 3 374 cm^-1 and at 673 and 403 cm^-1, respectively. The A_{3 210}/(A_{3 210}+A_{3 374}) values in the middle and last stages were lower than those in the initial stage, and the A₆₇₃/(A₆₇₃+A₄₀₃) value showed a slightly increased trend among stages. These results suggest that the localized hydrogen bonding of water molecules may have been disrupted, which at a macroscopic level may have enhanced hydrogen bonding network formation due to interactions with coexisting components. The two-dimensional plot of A_{3 210}/(A_{3 210}+A_{3 374}) against A₆₇₃/(A₆₇₃+A₄₀₃) demonstrated that filtered soy sauce of different ages could be evaluated through the simultaneous analysis of the local water environment and the macroscopic water structure.