The effect of ultrasound and freezing/thawing treatment on the physical properties of blueberries.

The aim of the study was to investigate the effect of ultrasound treatment and freezing/thawing on the physical properties of blueberries (Vaccinium corymbosum L.). Fruits were subjected to ultrasound treatment, mechanical freezing/thawing, and freezing/thawing with subsequent ultrasound treatment. Moisture, density, porosity, hardness, springiness, cohesiveness, chewiness, gumminess, and color of blueberries were analyzed. Ultrasound treatment and freezing/thawing significantly decreased particle density and increased porosity of blueberries (p < 0.05). Ultrasound treatment and freezing/thawing produced significantly softer, less chewy and gummy berries in relation to control sample (p < 0.05). All techniques induced considerable changes in the color of blueberries. The results indicates that ultrasound treatment performed after freezing/thawing, didn't exert any effect on the fruits in relation to freezing/thawing alone (p > 0.05); however, it is an interesting technique for processing fresh blueberries and an alternative to freezing/thawing, when the preservation of product quality is a priority or when rapid textural damage is required before diffusion processes.