Optimization of ultrasound‐assisted osmotic dehydration of white mulberry
Nargess Rahimi, Afifeh Ahraritabas, Elham Ansarifar
Abstract
The study aimed to optimize the ultrasound-assisted osmotic dehydration process of white mulberry using response surface methodology. Effects of three variables including ultrasonic treatment time (10, 20, and 30 min), osmotic solution concentration (25, 42.5, and 60% w/w), and frequency intensity (10%–90%) were investigated. Three responses were studied: water loss (WL), sugar gain (SG), and color parameters (a*, b*, L*, and ΔE). Results represented that, in comparison with the osmotic dehydration alone, the application of ultrasonic treatment reduced the total processing time and increased effective water diffusivity. Results revealed that frequency intensity had significant effects on all response variables except for L* and b*. Increasing the frequency intensity led to increased WL (10 times) and ΔE in the samples and a decrease in SG (2.8 times). It was also observed that time–concentration interaction term of response models is statistically significant for all responses except for ΔE, a*and b*, while time–amplitude interaction term was statistically significant for ΔE, alone. Finally, multi objective optimization according to the response surface models showed that the best conditions are osmotic solution concentration: 60%, frequency intensity: 75% and ultrasound time: 10 min. At this optimum conditions, WL, WR, SG, a*, b*, L* and ΔE were found to be 0.127%, 0.097%, 0.03%, −3.700, 32.071, 81.969, and 3.955, respectively. Novelty impact statement As an effective method for pretreatment of fruits, the ultrasound-assisted osmotic dehydration (UAOD) technique of whit mulberry was optimized. Pretreated whit mulberry with maximum water loss, minimum sugar gains, and optimum lightness and color differences were obtained.