Direct and indirect power ultrasound assisted pre-osmotic treatments in convective drying of guava slices

Abstract

Application of ultrasound to osmotic dehydration of guava slices via indirect sonication using an ultrasonic bath system and direct sonication using an ultrasonic probe system was studied. Pre-treatments were designed in three osmotic solution concentrations of 0, 35, and 70 °Brix at indirect ultrasonic bath power from 0 to 2.5 kW for immersion times ranging for 20-60 min and direct ultrasonic probe amplitudes from 0 to 35% for immersion times of 6-20 min. The calculated ultrasound intensities from calorimetric ultrasound power dissipated indicated that direct sonication was more intensive than indirect sonication. The general linear model (GLM) showed that ultrasound input (power and amplitude), osmotic solution concentrations, and immersion time increased the water loss, solid gain, and total colour change of guava slices significantly with P < 0.0005. Indirect sonication in osmotic solutions contributed to high water loss and solid gain with acceptable total colour change than direct sonication. Applying ultrasound pre-osmotic treatment in 70 °Brix prior to hot-air drying reduced the drying time by 33%, increased the effective diffusivity by 35%, and decreased the total colour change by 38%. A remarkable decrease of hardness to 4.2 N obtained was also comparable to the fresh guava at 4.8 N.

Ultrasound-Assisted Air-Drying of Apple (Malus domestica L.) and Its Effects on the Vitamin of the Dried Product

“…Kek et al (2013) have studied the influence of ultrasound-assisted osmotic pretreatments on the convective drying of guava slices. Their results showed that the ultrasonic pretreated dried samples have presented the lowest vitamin C content due to leaching of solutes to the liquid media promoted by cavitation.…”

Effect of Ultrasound Waves on Drying Process and Selected Properties of Beetroot Tissue

“…Ponadto suszenie modyfikuje właściwości produktów pochodzenia roślinnego, redukuje ich masę i objętość, co jest korzystne ze względu na ograniczenie kosztów podczas magazynowania i transportu [3,5,14,29].…”

Ultrasound-assisted osmotic dehydration and convective drying of apples: Process kinetics and quality issues

“…For indirect sonication of food placed in the ultrasonic water bath, the ultrasound is transferred through water and affects the food immersed in the bath. The ultrasound applied to the bath with food first passes through the walls of the container, therefore its intensity inside the bath is lower than that of the ultrasound source (Feng and Yang, 2010;Kek et al, 2013;Santos et al, 2009). …”

“…When ultrasound is directly applied to a hypertonic solution with immersed samples, and there is no such a barrier as a probe system, strong cavitation near the tip of the probe may generate free radicals being detrimental to foods. The ultrasonic cpe.czasopisma.pan.pl; degruyter.com/view/j/cpe probe can deliver about 100 times much higher of US intensity than an ultrasonic bath (Kek et al, 2013;Santos et al, 2009). For indirect sonication of food placed in the ultrasonic water bath, the ultrasound is transferred through water and affects the food immersed in the bath.…”