Ultrasound-assisted extraction and gaseous ozone as preservation method for Roselle (Hibiscus sabdariffa L.) fruit juice

Abstract

Ultrasound extraction and ozone treatment are promising non-thermal hurdle technologies which can increase the extraction yield while minimizing the loss of nutritional qualities of Roselle fruit juice. Response surface methodology (RSM) was used to investigate the effect of ultrasound time and temperature on juice yield. The optimized points were found at 4.4 min and 22°C, where the extraction yield of the Roselle fruit juice achieved a maximum of 80%, 12% higher than the control sample without ultrasound treatment. Roselle fruit juice (unfiltered and filtered) was then ozone-treated with processing variable of treatment time (0–30 mins). The effects of processing variables on physicochemical characteristics of Roselle fruit juice were determined and no significant differences (P>0.05) in pH and titratable acidity (TA) were observed. However, significant effect (P<0.05) was found in total colour difference (TCD), ascorbic acid (AA), total phenolic content (TPC), and total anthocyanin content (TAC) with increased ozone treatment time. Nevertheless, the degradation of AA was less than 50%, which showed that ozone has the potential to retain a high amount of AA in Roselle fruit juice. Thus, the synergistic effects of ultrasound and ozone treatment on Roselle fruit juice should be carefully considered by processors prior to its adoption as a preservation technique.