Effect of innovative process technologies on pasteurization and shelf life of licorice sherbet

Effects of ultrasonication and high hydrostatic pressure (HHP), as alternative processing technologies, on the quality properties and shelf life of the licorice sherbet were investigated. Licorice sherbet samples were subjected to ultrasonication (50, 70 and 90% amplitude, 5, 25 and 45 min treatment time, 4, 22 and 40 °C temperature) and HHP (200, 350 and 500 MPa pressure, 3, 9 and 15 min treatment time, 4, 22 and 40 °C temperature), and then physical, chemical, microbiological and sensory analyzes were performed under different process conditions obtained by Box-Behnken design. Total mesophilic aerobic bacteria (TMAB) count which was initially between 5.61-5.76 log cfu/mL, showed a decrease of about 3 and 3.3 log cfu/mL after ultrasonication and HHP, respectively. The total count of yeast and mold (TYM) in licorice sherbet was decreased by 2.98 and 3.65 log cfu/mL after ultrasonication and HHP, consequently. The results were modeled using the response surface design, and the optimum conditions were determined for both process parameters. It was found that the dependent variables modeled for ultrasonication application were pH, conductivity, L*, a*, antioxidant activity, total phenolic content, reducing sugar, TMAB and TYM reduction, while the dependent variables for HHP application were yellow color composition, reducing sugar, Bacillus circulans and Candida tropicalis reduction. The optimum conditions of licorice sherbet for ultrasonication were determined as 89.55% amplitude, 45 min tretment time and 24 °C temperature, and the optimum conditions for HHP were 500 MPa pressure, 9.90 min treatment time and 18.5 °C temperature. Licorice sherbet samples were stored at 4 and 22 °C to determine shelf life at optimum conditions for both processes. Physicochemical (pH, conductivity, color (L*, a*, b*, C*, h°, ΔE), total acidity, turbidity) microbiological (TMAB, TYM) and sensory analyzes of the licorice sherbet were performed on the 0, 15, 20 and 25 days of storage. Control samples were deteriorated by the 15th day. The samples treated with ultrasonication at 4 °C started to deteriorate on the 17th day and the samples that treated with HHP were still consumable on the 20th day of storage at 4 °C. According to the findings, it was determined that ultrasonication and HHP applications were successful in increasing the shelf life of licorice sherbet.