Optimization of Process Parameters for Vacuum Freeze Drying of Kiwi Fruit

Drying has long been one of the most effective and widely used methods for food preservation. Among various techniques, vacuum freeze drying (VFD) offers the advantage of producing hygienic products while better preserving the original taste, appearance, color, and nutritional content, as well as achieving a higher rehydration rate. This study aims to optimize the VFD process for kiwi fruit to obtain high-quality products with improved appearance, color, taste, and nutritional retention at reduced cost. The Taguchi method was employed to identify optimal process parameters, including slice thickness (5, 7, and 9 mm), ramp rate (0.5, 1.0, and 1.5 °C/min), drying temperature (40, 50, and 60 °C), and drying rate (5, 10, and 15 °C/hr), using an orthogonal array with four factors at three levels each. Drying experiments were conducted above the eutectic point to ensure rapid temperature rise and efficient primary drying. The results showed that vacuum-freeze drying achieved the highest product quality at a slice thickness of 5 mm, a ramp rate of 0.5 ℃/min, a drying temperature of 60 ℃, and a drying rate of 15 ℃/hr.