Physical and biochemical properties of Yanang juice mixed with longan flower-honey following high pressure processing

This study investigated the effects of high hydrostatic pressure (HHP) at 400-600 MPa/25 and 50°C/20 min on physicochemical qualities and bioactive compounds retention in Yanang juice mixed with 10% (v/v) longan flower-honey. The results showed that the parameter (brightness) significantly increased in pressurized juices when compared to fresh juice, while the greenness (-a*) of all processed juices slightly decreased, in particular pressurized batches at 50°C. There was no significant difference in the pH values of fresh and pressurized juices. The levels of ascorbic acid and antioxidant capacity (DPPH and FRAP assays) decreased according to treatment severities, particularly the juices processed at milder-temperatures. The highest retention of total phenols and flavonoids was found in HHP treated juices at 600 MPa. This study also demonstrated that pressure could inactivate the indicator microorganisms including total plate counts, yeasts-moulds and fecal coliforms to levels conforming to the Thai Community Product Standard for Yanang juice.