Non-destructive evaluation of the internal fruit quality of black mulberry (Morus nigra L.) using visible-infrared spectroscopy and genetic algorithm

The present study aims at assessing a non-destructive optical method for determining the internal quality of mulberry juice. First, UV-IR spectra (300-1100 nm) were acquired for each sample with a spectral resolution of 2 nm. Then the calibration set, composed of 70 and 38 samples, was used as the validation set. Next, two types of pre-processing multiplicative scatter correction)MSC(and standard normal variate)SNV(were used before analysing the data with multivariate calibration methods of PLS and GA-PLS. The following results were obtained including the correlation coefficient (r) of 0.94, 0.89, 0.98, and 0.95 and root mean square error of validation (RMSEV) 1.31 degrees Brix, 0.52, 0.014, and 0.014 for total soluble solid (TSS), titratable acidity (TA), ascorbic acid (AA), and total anthocyanin content (AC) of mulberry juice, respectively. After that, GA-PLS was applied to select the efficient spectral regions. Model using 31 variables and 15 factors presented and yielded the best prediction results. The best combinations of 21 spectral intervals among 40 intervals selected by GA-PLS also yielded good results with RMSEV = 0.03096, r = 0.96; RMSEV = 0.062, r = 0.98, RMSEV = 0.041, r = 0.98; RMSEV = 0.0006, r = 0.96 for TSS, AA, TA, and AC of mulberry juice, respectively. Finally, it was concluded that using the UV-IR measurement technique, spectral range (300-1100 nm), it was possible to assess the quality characteristics of mulberry juice.