Nondestructive Determination of Soluble Solids Content in Watermelon Using Vis/NIR Diffuse Transmittance

摘要

A low-cost commercially available Visible/Near Infrared (Vis/NIR) spectrometer was fitted with special light source and fiber optics to measure Vis/NIR diffuse transmittance spectra in intact watermelons. With this device the potential of the diffusetransmittance method to determine the Brix value in watermelon was examined. To reduce the fruit size effect which affected the spectra, the 2nd derivative spectra were normalized by being divided by 2nd derivative value at 827nm, which had a high correlation to the volume of the watermelon. 75 "ZaochunHongyu (ZH) " watermelons which were purchased from the local fruit market were used in the experiment. 50 watermelons were used for calibration and the others for prediction. Partial least squares (PLS)analysis was carried out to relate the Brix value to the normalized 2nd derivative spectra. The correlation coefficient was 0.947 with a root mean square errors of calibration (RMSEC) of 0.313°Brix. The root mean square errors of prediction (RMSEP) was0.413°Brix. It is concluded that the Vis/NIR transmittance method yields a satisfied estimate of the Brix value in intact watermelons.