Ultrasound as a Pretreatment Method to Improve Drying Kinetics and Sensory Properties of Dried Apple

Abstract

The effect of ultrasound pretreatment on drying kinetics and physical properties as color and rehydration rate of dried apple slices was investigated. Apple samples var. Idared were submitted to ultrasonic treatment using 21 and 35 kHz for 30 min in an ultrasound bath securing sound intensity of 3 and 4 W/cm 2 , respectively. After pretreatment, the material was dried in a convective oven at 70C and at an air velocity of 2 m/s. The sonication reduced drying time by 13-17% in comparison with the untreated sample. Ultrasound treatment changed the color of apples tissue by decreasing the value of a* parameter and increasing the dried material lightness, chromaticity and the value of b* coefficient. Moreover, obtained results showed that there was a significant effect of pretreatment on rehydration properties as compared with untreated apple tissue. PRACTICAL APPLICATIONSThe most energy-consuming processes existing in the food technologies are the processes based on heat and/or mass transfer, for instance drying. Thus, a lot of attention is paid by researchers to conserve the energy and minimally change the physicochemical properties of food, which shape its quality. Additionally, increasing growth of consumers' expectations and their nutritional knowledge stimulate to seek some new solutions even more. Aforementioned is a reason why nonthermal technologies as ultrasound seem to be the one of the most interesting propositions.

Ultrasound assisted osmotic dehydration of organic cranberries (Vaccinium oxycoccus): Study on quality parameters evolution during storage

“…This effect was noticed by Prinzivalli, Brambilla, Maffi, Lo Scalzo, and Torreggiani (2006) in strawberry slices. As reported in the literature in the case of dehydrated apples and carrots, the pre-treatment with ultrasound leads to an increase in lightness (L*) compared to the untreated fruit (Fijalkowska, Nowacka, Wiktor, Sledz, & Witrowa-Rajchert, 2016). In our case, significantly higher values of L* for untreated and US treated samples were observed only at the 8th week of storage.…”

Effect of ultrasound treatment on microstructure, colour and carotenoid content in fresh and dried carrot tissue

“…The effective moisture diffusion coefficient can be considered as a parameter that characterizes the drying rate [17,32]. The highest value of this parameter equalled to 5.00 Á 10 À10 m 2 /s and it was observed for untreated sample.…”

“…The effective water diffusion coefficient (D eff ) was calculated using TableCurve 2D v5.01 software on the basis of the simplified Fick's diffusion equation [32]: [33].…”

Analysis for Difficulty during Freeze-Drying Feizixiao Lychees

“…Ultrasound treatment can decrease the drying time and increase the quality of dried samples [21,30,31]. So, ultrasound was applied to treat Feizixiao lychee pulp in order to improve the appearance of FD pulp.…”

“…It indicated that ultrasound pretreatment prior to freeze-drying can improve the efficiency of FD and the stability during storage of FD pear. Ultrasound pretreatment did reduce drying time by 13-17%, increased the lightness, decreased the brown pulp, and improved the rehydration properties of dried apple [21].…”