Effect of pretreatments and drying on shrinkage and rehydration kinetics of ginger (Zingiber officinale)

Abstract In this study, it was aimed to understand the effect of drying temperature (40, 50, and 60°C) and pretreatments such as conventional blanching (60°C for 5 min) (CB), microwave‐assisted blanching (430 W for 2 min) (MAB), and ultrasound (amplitude: 60%; time: 15 min) (US) conditions on shrinkage and rehydration behavior of ginger slices. In all treatment combinations, the volumetric shrinkage of ginger slices was well described by the quadratic equation as a function of moisture content. From the experimental study, it was found that the ginger slices pretreated with US had shown the lowest percentage of shrinkage in length (6–7%), breadth (41–43%), and volume (64–65%) at three different drying temperatures, following that control (7–10%, 44–45%, and 66–71%), CB (17–19%, 55–57%, and 80–81%), and MAB (16–23%, 46–53%, and 76–80%) slices have higher volumetric shrinkage. In rehydration, the Peleg's, exponential, and Vega‐Galvez models comparatively well describe the rehydration kinetics of ginger slices as a function of rehydration time. The US treated samples dried at 60°C have the higher rehydration ratio (RR) of 4.886 at 35°C rehydration temperature. The relationship between the Peleg's kinetic rates constant ( k 1 ), and various treatment conditions was estimated. The rehydration ratio of ginger slices lies between 2.5 and 5. Compared to other pretreatments and drying conditions, US treated samples dried at 60°C have better quality in terms of volumetric shrinkage and rehydration ratio. Practical Applications When it comes to the preservation of fresh agricultural products, drying is the most common method. Studying dried product quality using physical criteria such as shrinkage and rehydration helps to understand the textural and physical nature of foods. This study will aid in selecting better process parameters to obtain higher‐quality products and information on ginger shrinkage and rehydration behavior. The shrinkage and rehydration behavior of ginger slices have been satisfactorily described using mathematical models. A quadratic equation best describes the shrinkage behavior. The rehydration property of ginger slices is well represented by the Peleg's, exponential, and Vega‐Galvez models. The ginger slices pretreated with US treatment undergone fewer shrinkage changes and have higher water uptake in a minimum rehydration period. They can be used in ready to cook products.