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

Abstract

Cranberries are appreciated for their high amount of antioxidants such as flavonoids, anthocyanins,phenolic acids, carotenoids and vitamins. However, due to their sour and tart taste they request to beprocessed into sweeter dried fruits in order to be acceptable for the consumers. The aim of this work wasto analyse the effect of ultrasound assisted osmotic dehydration on mass transfer parameters and onquality characteristics during storage of cranberries. Ultrasound treatment was performed at the fre-quency of 21 kHz for 30 min in three osmotic solutions - 61.5% sucrose, 30% sucrose with an addition of0.1% of steviol glycosides and 40% trehalose on cut in half cranberries. Afterwards, the cranberry sampleswere subjected to osmotic dehydration process at 40C for 72 h. The osmodehydrated samples both withor without ultrasound pre-treatment were collected and stored at 10C in climatic chamber in micro-perforated plastic bags (PLA) for 8 weeks. The weight reduction, dry matter, water activity, colour, andmicrobiological analysis were performed after 1, 2, 4 and 8 weeks of storage. The obtained resultsindicated that ultrasound application significantly affected the mass transfer parameters during osmotictreatment, as well as it did the type of osmotic solution used. Thermal analysis showed variations insugar melting temperature and enthalpy as a result of osmotic treatment and storage. During the storage,lower weight loss and higher lightness were observed in US pre-treated samples. The sample thatpreserved the best chemico-physical and microbiological characteristics during storage was the onetreated with 61.5% sucrose solution, due to its lowest water activity