EFFECT OF ULTRASOUND AND ACID PRETREATMENTS DURING DEHYDRATION ON QUALITY PROPERTIES OF QUINCE

Several methods are employed to remove the moisture from organic or non-organic materials, in a variety of industrial applications. Among all, dehydration of fruits is an alternative to decline post-harvest loss of fruits and also a process to produce dried fruits, which can be directly consumed or become part of foodstuffs like cakes, and many others. In particular, drying provokes a series of changes in materials, such as oxidation, browning, or loss of nutritional-functional properties. Ultrasound is famous to have a significant effect on the rate of various processes. Quince is a fruit which is rich in polyphenols, organic acids, and amino acids with important health benefits. The present study examined the effect of ultrasound and blanching pre- treatments prior to convective drying on quality  properties  of dehydrated quince slices. A completely randomized design was used to address the effect of time of sonication (10−30 min), temperature (40−60°C), and anti-browning agents including acetic, citric, and ascorbic acids as well as distilled water on quality properties of dehydrated quince slices. The obtained results revealed that the shortest drying time (270.33±35.59 min) and the highest total phenolic content (57.29±12.72 mg GAE/ml) were recorded for samples exposed to the ascorbic acid solution. Comparison of the pre-treated and control samples indicated that the highest rehydration ratio (2.75±0.29 %) was achieved by blanched samples in acetic acid solution. The use of citric acid solution led to the highest score in the taste (3.45±1.1), color (3.84±0.9), and texture (3.47±1.02) of quince slices on the basis of a 5- point hedonic scale. The obtained results depended on both ultrasound and the type of blanching solution. Citric and acetic acid samples indicated the highest values of the sensory evaluation and water loss, respectively.