Physiological Changes of Date Fruit during Ripening On-tree
The degree of ripeness is a key factor for consumption, marketing, and minimal processing of fruits. This study was conducted to describe the physicochemical changes (geometrical and gravimetrical properties) and the relationships between different ripeness indexes i.e. pH, total soluble solids (TSS), titratable acidity (TA), firmness, dry weight content (DW) and color of date fruit during four ripening periods on-tree including Kimri, Khalal, Rutab and Tamr stages. These four stages were selected by visual fruit color and days after anthesis (DAA). Duncan’s multiple tests was performed to separate means at a 5% level of significance. A correlation analysis by Pearson correlation matrix method was also made between the colorimetric ripeness parameters and pH, TSS, TA, firmness and DW from Kimri to Tamr stage. Significant (p<0.05) decrease in geometrical properties (except width) and gravimetrical properties (Fruit mass, true volume of fruit) was observed during ripening. Parameters as L*, b*, C*, linearly decrease during ripening; conversely, h° decreased as a result of color change from green to black. Firmness decreased due to gradual softening of fruit tissues, it was higher at Kimri stage. Additionally, pH, TSS and TA values increased when ripening was developed. The results of Pearson correlation between ripeness indexes allowed to establish model equations for destructive tests values such as TSS and firmness with nondestructive test such as CIEL*a*b* and CIEL*C*h° scales. The results show that studied models are a feasible alternative to be used as a practical detection system in the ripening, avoiding eventual human errors.