Shelf life, physicochemical, microbiological and antioxidant properties of purple cactus pear (Opuntia ficus indica) juice after thermoultrasound treatment

Abstract

The objective of this study was to evaluate changes in color, betalain content, browning index, viscosity, physical stability, microbiological growth, antioxidant content and antioxidant activity of purple cactus pear juice during storage after thermoultrasonication at 80% amplitude level for 15 and 25min in comparison with pasteurized juice. Thermoultrasound treatment for 25min increased color stability and viscosity compared to treatment for 15min (6.83 and 6.72MPa, respectively), but this last parameter was significantly lower (p<0.05) compared to the control and pasteurized juices (22.47 and 26.32MPa, respectively). Experimental treatment reduced significantly (p<0.05) sediment solids in juices. Total plate counts decreased from the first day of storage exhibiting values of 1.38 and 1.43logCFU/mL, for 15 and 25min treatment, respectively. Compared to the control, both treatments reduced enterobacteria counts (1.54logCFU/mL), and compared to pasteurized juice decreased pectinmethylesterase activity (3.76 and 3.82UPE/mL), maintained high values of ascorbic acid (252.05 and 257.18mg AA/L) and antioxidant activity (by ABTS: 124.8 and 115.6mg VCEAC/100mL; and DPPH: 3114.2 and 2757.1μmol TE/L). During storage thermoultrasonicated juices had a minimum increase in pectinmethylesterase activity (from day 14), and exhibited similar total plate counts to pasteurized juice. An increase of phenolic content was observed after 14days of storage, particularly for treatment at 80%, 25min, and an increase in antioxidant activity (ABTS, DPPH) by the end of storage.