Pulsed pressure osmotic dehydration enhances mass transfer and impacts on subsequent pulsed vacuum drying kinetics and quality attributes of kiwifruit slices

Abstract

Proper processing is essential in mitigating postharvest losses and enhancing the value of kiwifruit due to its high perishability and susceptibility to rotting after harvest. Preserved kiwifruit slices are widely recognized as one of the most popular kiwifruit products. Osmotic dehydration and drying are two essential operations for its production, however, the traditional normal pressure osmotic dehydration (NPOD) and hot air drying often result in low production efficient and poor quality. In this study, two emerging techniques namely pulsed pressure osmotic dehydration (PPOD) pretreatment and pulsed vacuum drying (PVD) were employed to improve the production of preserved kiwifruit. The effect of PPOD on the weight reduction, water loss, and solids gain during osmotic dehydration pretreatment of kiwifruit slices were evaluated. In addition, its influence on subsequent PVD drying kinetics and quality attributes was also investigated. Results revealed that the application of PPOD treatment substantially enhanced mass transfer in kiwifruit, as evidenced by a 3.78/100 g increase in solids gain and a 6.62% rise in soluble sugar content at 40°Brix compared to normal pressure osmotic dehydration (NPOD) treatment at the same duration. Both the Weibull and Page models exhibited a high degree of fitting accuracy (R 2 > 0.99) in describing the drying process of kiwifruit with osmotic dehydration pretreatment. However, the parameter α indicated that NPOD pretreated kiwifruit dried more rapidly, resulting in a reduction of 29.68 min compared to PPOD pretreatment at 40°Brix. Furthermore, PPOD treatment well demonstrated an enhancement in texture with reduced hardness and chewiness, as well as an improvement in rehydration ratio compared to NPOD treatment. Notably, PPOD treatment led to a 4.99% increase in vitamin C retention compared to NPOD treatment at 40°Brix. The findings suggest that PPOD is an effective pretreatment method for the production of preserved kiwifruit as it enhances both osmotic dehydration and quality attributes.