Ultrasound-assisted osmotic dehydration, followed by convective drying of papaya: effect on physicochemical and functional quality parameters

Abstract

Papaya is a rich source of nutrients, antioxidants, and vitamins; however, it is highly perishable and hence needs to be preserved using suitable unit operations. Drying is an economical method of papaya treatment, but results in the loss of essential nutrients and also degrades its pigments, color, and texture. Therefore, this work aims to utilize ultrasound and osmotic dehydration as pretreatment strategies to preserve the rich composition of papaya during conventional hot air drying. The dried papaya slices were evaluated for moisture content, water activity, total phenolic content, β-carotene, color, antioxidant activity, microstructure, and texture. Results showed that sample pretreatment with 33 kHz ultrasound frequency and dehydrated with 35°Brix osmotic solution resulted in lower moisture content (< 12% w.b.) and water activity (< 0.41), high phenolic content (88.5 mg GAE/mL), high β-carotene content (184.54 mg/g) and antioxidant capacity (48.3%), and preserved color after drying. The texture (hardness) of the pretreated samples was also more desirable from an industrial standpoint, which was further validated using SEM micrographs that showed a more porous structure. The study concludes that pretreatment of papaya slices with ultrasound and osmotic dehydration is recommended before drying.