Vanilla content evaluation in cured bean by near-infrared technique
2016
Wongsheree, T. | Rittiron, R. | Wongs-Aree, C. | Thongtheing, T.
Vanillin content is the major quality attribute of cured vanilla beans. However, bean quality is commonly assessed visually. The current standard method for analysis of vanillin content is destructive, slow, and impractical. Therefore alternatively non-destructive methods like near-infrared spectroscopy (NIRS) for determination of vanillin and dry matter content of cured beans should be commercially beneficial. The light absorbance of 130 beans was measured by both a portable NIR spectrometer and a Fourier Transform (FT)-NIR spectrometer in the reflection mode for development of calibration equation, compared with the dry matter and the vanillin content chemically extracted and analysed by HPLC standard method. The Partial Least Squares Regression (PLSR) models were based on the spectra of 99 beans, with validation on further 31 beans. The model developed using the portable spectrometer (wavelength region of 600-1,100 nm) allowed determination of the vanillin content with standard error of calibration (SEC) = 2.58%, standard error of prediction (SEP) = 2.77%, and average error (bias) = 0.60%. The calibration statistics for the FT-NIR spectrometer (wavelength region of 1200-2500 nm) were: SEC=2.11%, SEP=2.03%, and bias=-0.07%. For the attribute of dry matter (DM), a correlation coefficient (R) of 0.96 was obtained for both spectrometers. Both vanillin and DM models could be used to predict the contents without significant difference between actual and NIR predicted values at 95% confidence level. NIR spectroscopy has a high potential for evaluation of DM and vanillin content in cured vanilla bean.
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