Effect of Ultrasound and Ultrasound-assisted Osmotic Dehydration on Infrared Radiation Drying Characteristics of Peach Slices
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Abstract:
To explore the effect of ultrasound (UL) and ultrasound-assisted osmotic dehydration (ULOD) pretreatments on water transfer in peach slices and the drying characteristics of infrared radiation drying, samples were pretreated with UL and ULOD for different time followed by infrared radiation drying at 80 ℃. Low-field nuclear magnetic resonance (LF-NMR) was used to measure the transverse relaxation times (T2) of the pretreated peach slices. Changes in water status and distribution were analyzed, the drying characteristics curve was obtained, and the effects of water status and distribution on the drying characteristics were explored. The results showed that UL decreased the soluble solid content, and ULOD significantly improved the soluble solid content and decreased the water content. Both pretreatments affected the water status and distribution. UL increased the transverse relaxation times of immobilized water (T22) and free water (T23), indicating that the degree of freedom of water increased. As a result, UL enhanced the drying rate and increased the water effective diffusion coefficient (Deff). ULOD decreased the transverse relaxation time of bound water (T21), immobilized water (T22), and free water (T23). The free water content was significantly reduced, and the immobilized water and bound water content increased relatively, thus reducing the drying rate and decreasing the Deff of infrared radiation drying. This study provides the theoretical basis for the study of the effects of UL and ULOD pretreatments on water transfer and diffusion characteristics of fruite slice treated by infrared radiation drying.
