Nondestructive evaluation of changes in total flavonoid, total phenol and DPPH scavenging activity during loquat (Eriobotrya japonica Lindl.) fruit development by chlorophyll fluorescence and RGB intensity values

ABSTRACT Loquat (Eriobotrya japonica Lindl.) is a kind of subtropical fruit cultivated in many countries. This study aimed to evaluate the changes in the content of total phenol, total flavonoid, and 1,1-Diphenyl-2-picrylhydrazyl (DPPH), scavenging activity during the seven developmental stages and to determine the optimum harvesting time of loquat fruits by using chlorophyll fluorescence and Red Green Blue (RGB) intensity detection. Our results revealed a high correlation between chlorophyll fluorescence parameters and the internal chemical parameters (total phenol, total flavonoid, and DPPH scavenging activity) in loquat. The best prediction model from ST1 to ST5 for total flavonoid with variable fluorescence (Fv) and Fv / maximum fluorescence (Fm), R 2 = 0.79, and for DPPH scavenging activity with Fm, Fv, and Fv/Fm, R 2 = 0.92 was achieved, respectively. Total phenol correlated with minimum fluorescence (Fo) and Fv from ST4 to ST7, with R 2 = 0.99. Red Green Blue (RGB) intensity is also highly correlated with the internal chemical parameters. Both total phenol and DPPH radical scavenging activities had the best correlations with the B intensity value (R 2 = 0.998, R 2 = 0.970) in the ST1-ST4 period, respectively. Total phenols and total flavonoids had the best correlation with the G intensity value (R 2 = 0.909, R 2 = 0.986) in the ST5-ST7 period, respectively. In conclusion, developmental stage ST5 is the optimum harvesting time for loquat fruit, and chlorophyll fluorescence and RGB intensity are both noninvasive measurements for quality assessment during the loquat development period and for the prediction of the optimal time for harvesting loquat fruit.