engleski

Influence of high intensity ultrasound as drying pretreatment on the texture properties of pears

High intensity ultrasound as novel food processing technology is promising in the field of drying of food products. Pretreatment of foodstuff using ultrasonics can significantly shorten drying time, which potentially have economical (electricity and time) and nutritional (lower drying temperatures, less impact on nutritional content) benefits. Cavitation produced by ultrasound increase number of pores and pore size which effectively impacts diffusion speed of water from core to the surface of fruits. However, changes in fruit matrix can have negative impact on textural properties of fruit. Main goal of this research is investigation of influence of ultrasonic pretreatment on drying time and texture of pears, and finding optimal processing parameters for drying. Experiments include pretreatment of pear samples using 20 to 100 % of maximal ultrasonic power (400 W) for 4 minutes. All samples were dried in the infrared dryer at 60 oC. Using instrumental texture analyzer samples were cut and hardness and elasticity were calculated based on obtained graphs. It is evident that ultrasound had significant impact on shortening of drying time (from 175 to 80 min). However this also mean that at the 80 % and 100 % of maximal power there are significant changes in textural properties, mainly in hardness and elasticity. Optimal amplitude was 60 %, which shortened drying time to 110 min, while retaining most of the hardness and elasticity compared to original untreated fruit.

ultrasound; drying; pear; texture analysis

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