QUALITY PARAMETERS AND DRYING KINETICS OF ULTRASOUND PRETREATED FERMENTED BLACK TABLE OLIVES

Abstract

The effect of ultrasound (US) pretreatment on microwave drying parameters including drying rate, moisture ratio and effective diffusivity and quality properties such as total phenolic and color parameters (L*, a*, b*, C, ΔE and H°) of black table olive slices were determinated. 10 minutes ultrasound pretreatment decreased drying time of black table olive slices by 31.81%, 41.37% and 42.85% compared to control samples dryed at 180, 450 and 800 W, respectively. Weibull and Diffusion models could precisely fit the drying behavior of black table olive slices (R2 > 0.9950). Microwave drying  had a negative effect on phenolic contents of olives, whereas  US pretreatment preserved phenolic compounds and enhanced the color parameters of samples. Higher effective diffusivity (Deff) values were obtained when the drying was combined with US pretreatment. Microwave drying with ultrasound pretreatment could improve drying process, since it accelarated drying rate and preserved the phenolic content and color parameters.