Abstract
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.
Highlights
Blueberries (Vaccinium corymbosum L.) are widely consumed perishable fruits which are rich in anthocyanins, bioactive compounds that are responsible for the desirable reddish blue color of blueberry fruits; color measurement can provide useful information about the content of these compounds (Rolle and Guidoni, 2007; Zielinska and Michalska, 2016)
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); 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
Ultrasound treatment did not exert a significant influence on the moisture content of blueberry fruits or the moisture content after freezing/thawing in comparison to frozen/thawed blueberries (p [ 0.05)
Summary
Blueberries (Vaccinium corymbosum L.) are widely consumed perishable fruits which are rich in anthocyanins, bioactive compounds that are responsible for the desirable reddish blue color of blueberry fruits; color measurement can provide useful information about the content of these compounds (Rolle and Guidoni, 2007; Zielinska and Michalska, 2016). Traditional methods of initial pretreatment include freezing/thawing of blueberries, which significantly reduces drying time and specific energy consumption of drying relative to drying without initial pre-treatment (Feng et al, 1999; Zielinska et al, 2015). This method significantly decreases cuticle thickness (to approximately half of the initial value). Compared to traditional methods, increased heat and mass transfer processes can be observed during ultrasound treatment (Ensminger, 1988; Li et al, 2010). It depends on the treatment time, ultrasound intensity and type of material. The effect of ultrasound treatment on the physical properties of blueberry fruits has not yet been described
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