Nondestructive rapid analysis for the determination of
total nitrogen, soluble solids, salt content, and alcohol content in soy sauce
was examined using near infrared (NIR) transmittance spectroscopy. Calibration
equations were obtained by multiple linear regression of measured values and NIR
absorbance values (log (1/T) ) . Second derivatives of absorbances (d 2 log
(1/T) ) were also used as well as log (1/T).
The standard errors of prediction (SEP)
were 0.027g/100g for total nitrogen, 0.20’ Brix for soluble solids, 0.I9%w/v
for salt content, and 0.14%v/v for alcohol content.
Assignment of selected wavelengths for
calibration equations were confirmed by using an aqueous solution of
polypepton-S, sodium chloride and ethanol as authentic spectra. It was
suggested that wavelength selection should be based on its ability to withstand
interference from other compounds rather than its sensitivity.