Measurement of soluble solids content in watermelon by Vis/NIR diffuse transmittance technique |
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| Authors: | Tian Hai-qing Ying Yi-bin Lu Hui-shan Fu Xia-ping Yu Hai-yan |
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| Institution: | (1) School of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, 310029, China |
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| Abstract: | Watermelon is a popular fruit in the world with soluble solids content (SSC) being one of the major characteristics used for
assessing its quality. This study was aimed at obtaining a method for nondestructive SSC detection of watermelons by means
of visible/near infrared (Vis/NIR) diffuse transmittance technique. Vis/NIR transmittance spectra of intact watermelons were
acquired using a low-cost commercially available spectrometer operating over the range 350–1000 nm. Spectra data were analyzed
by two multivariate calibration techniques: partial least squares (PLS) and principal component regression (PCR) methods.
Two experiments were designed for two varieties of watermelons Qilin (QL), Zaochunhongyu (ZC)], which have different skin
thickness range and shape dimensions. The influences of different data preprocessing and spectra treatments were also investigated.
Performance of different models was assessed in terms of root mean square errors of calibration (RMSEC), root mean square
errors of prediction (RMSEP) and correlation coefficient (r) between the predicted and measured parameter values. Results showed that spectra data preprocessing influenced the performance
of the calibration models. The first derivative spectra showed the best results with high correlation coefficient of determination
r=0.918 (QL); r=0.954 (ZC)], low RMSEP 0.65 °Brix (QL); 0.58 °Brix (ZC)], low RMSEC 0.48 °Brix (QL); 0.34 °Brix (ZC)] and small difference
between the RMSEP and the RMSEC by PLS method. The nondestructive Vis/NIR measurements provided good estimates of SSC index
of watermelon, and the predicted values were highly correlated with destructively measured values for SSC. The models based
on smoothing spectra (Savitzky-Golay filter smoothing method) did not enhance the performance of calibration models obviously.
The results indicated the feasibility of Vis/NIR diffuse transmittance spectral analysis for predicting watermelon SSC in
a nondestructive way.
Project supported by the National Natural Science Foundation of China (No. 30370371) and Program for New Century Excellent
Talents in University (No. NCET-04-0524), China |
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| Keywords: | Diffuse transmittance Visible/near infrared Nondestructive detection Soluble solids content Watermelon |
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