Textural properties of infra red dried apple slices as affected by high power ultrasound pre-treatment

Abstract

Drying is a process frequently used in food industry, often based on the use of conventional methods using heat exchange by conduction or convection. This kind of method may lead to quality loss in structure, texture and  sensory characteristics of final products. Consequently, the need for research of new drying methods arises.  One of such methods is power ultrasound aided drying. The aim of this work was to investigate the impact of  high power ultrasound pre-treatment on drying rate and textural properties of the infra red dried apple slices.  Ultrasound device working at a frequency of 24 kHz with a power capacity of 200 W was used for ultrasound  pre-treatment. The amplitudes used for ultrasonic pre-treatment were 50 and 100%. The results showed that  the use of different amplitudes of ultrasound reduces the time of drying and allows elimination of more water  from the apple slices. Usage of 50 and 100% of ultrasonic amplitude in great extent shortened the duration of  drying (up to 40%). The results showed that hardness of samples gradually increases (50% amplitude –  97.260 N; 100% of amplitude – 217.90 N) with increase of ultrasound intensity. As a result, hardness of  untreated apple slices (41.037N) was significantly lower (p < 0.05).

Key words: High power ultrasound, amplitude, drying, apple.