Abstract

This study was conducted to investigate compositional changes and antioxidant capacities of pomegranate fruit (‘Bhagwa’ and ‘Ruby’) at five distinct stages of maturity over two growing seasons. Total soluble solids (TSS), pH, titratable acidity (TA), phenolic concentrations, antioxidant capacity and aroma volatile constituents were investigated. Principal component analysis (PCA) and Pearson correlation were used to visualize the changes in major chemical indices and the relationship among them. Results show that major compositional changes in fruit are developmentally regulated. Significant increases in total soluble solids (TSS), coupled with significant decline in titratable acidity (TA) and total phenolics (TP) occurred with advancing maturity. Fruit at advanced maturity stages were characterized by intense pigmentation of peel and aril, which coincided with maximum accumulation of anthocyanins. TSS and TA showed strong relationships with most of the chemical indices, each showing significantly (p < 0.05) strong correlations with phenolic components as well as with the antioxidant capacity (FRAP and DPPH) measured. There were no significant (p < 0.05) seasonal effects on juice absorbance (colouration) and TA for ‘Bhagwa’ as well as juice absorbance, TSS, TSS/TA and BrimA for ‘Ruby’. In combination, the identified maturity indices (absorbance, TSS, TSS:TA and BrimA level) would account for the evolution of juice colour, flavour and taste. The identified maturity indices for each cultivar could aid the search for reliable maturity markers to determine fruit readiness for harvest. 

Key words: Antioxidant capacity, BrimA, ripeness, seasonality, pomegranate, South Africa.

Abbreviation

Abbreviations: TSS, Total soluble solids; TA, titratable acidity; PCA, principal component analysis; TP, total phenolics; PJ, pomegranate juice; TGC, total gallotannins concentration; TAC, total anthocyanin concentration.