Concurrent Osmotic Dehydration and Vacuum Drying of Kiwi Fruit (Actinidia Deliciosa cv. Hayward) Under Far Infrared Radiation: Process Optimization, Kinetics and Quality Assessment

A novel dehydration protocol for Kiwi fruit (KF) involving simultaneous osmotic dehydration (OD) and vacuum drying (VD) viz. ODVD under far‐infrared (FIR) radiation has been developed. This is the first report for OD of KF using fructose as osmotic solution. The ODVD process had been optimized using Taguchi orthogonal design to obtain KF with minimum moisture content in minimum time. Dehydrated KF with 4.70% (w/w) moisture content was produced in 100 min ODVD time at 50°B, 40°C radiator temperature and 20 mbar chamber pressures. The optimally dehydrated KF demonstrated a significant increase in the ascorbic acid content (16.60%), total phenolic content (13.09%), total flavonoid content (21.01%) and radical scavenging activity (5.85%). At optimal condition, Newton's drying model could best represent the dehydration kinetics. The high moisture diffusivity viz. 9.78 × 10−10 m2/s and low activation energy viz. 10.78 kJ/mol computed through Fick's law in ODVD indicated a fast and energy‐efficient process. Practical Applications Kiwi is an important commercial, seasonal and tropical fruit. It is marketed in the forms of marmalade, jam, jellies, etc. which are usually prepared using chemical preservatives. The use of such preservatives may be avoided through effective dehydration of Kiwi by concurrent osmotic‐dehydration (OD) and vacuum drying (VD) [ODVD]. The application of simultaneous ODVD under far‐infrared (FIR) radiation improves the mass and heat transfer rates and thereby hastens the inflow of external solute and outflow of internal moisture facilitating faster dehydration and compositional reforms. The application of FIR radiation reduces the drying time appreciably making the process energy‐efficient and economically sustainable. The evaluated optimal conditions and associated drying kinetics of the novel ODVD process enables design of drying equipment for similar foodstuffs. The qualities of the dehydrated Kiwi fruit viz. ascorbic acid, phenols, flavonoids and antioxidant activity conform to market status.