Investigation of the Effect of Immersion and Ultrasound Pretreatments on Some Quality Characteristics of Pears Dried in Vacuum-Assisted Double-Sided Infrared Dryer

In this study, the effects of different immersion solutions (maltodextrin and ascorbic acid), solution concentrations (7 and 14% for maltodextrin, 0.5 and 1% for ascorbic acid), immersion times (1, 5, and 10 minutes) and ultrasound amplitudes (0%, 50% and 100%) applied as pretreatment on pears dried in a vacuum-assisted two-way infrared dryer were investigated. Moisture, pH, and acidity values of fresh pear were determined as 81.15%, 4.50 and 0.26%, respectively. Glucose, fructose, sucrose, and total sugar values were calculated as 14.76, 26.51, 6.63, and 47.90 g 100g-1 DM, respectively. Total phenolic content amount, DPPH, and ABTS values were found to be 2461.35 mg GAE kg-1 DM, 407.76, and 206.79 mmol Trolox eq. kg-1 DM. Increasing ascorbic acid concentration prevented HMF formation with increasing ultrasound amplitude and duration, while increasing maltodextrin concentration increased HMF content, especially with increasing immersion duration. In terms of individual phenolics, ellagic acid was not detected in fresh pears, while ellagic acid was detected in dry samples together with chlorogenic acid and rutin. As the ultrasound duration applied in pretreatments increased, the amounts of all individual phenolic compounds in the samples, except for rutin, increased. In the sensory evaluation, the highest approval score was obtained from samples kept in 0.5% ascorbic acid solution and 50% ultrasound amplitude for 10 minutes. As a result, it was determined that the quality of pears dried in vacuum-supported two-way infrared dryers could be increased with the pretreatment combinations, and products with low HMF, high phenolic compounds, antioxidant activity, and approval levels could be produced.