Effects of pulsed electric fields pretreatment and drying method on drying characteristics and nutritive quality of blueberries

Fresh blueberries were pretreated with pulsed electric fields (PEF) at 2 kV/cm and then dried at 45, 60, and 75 degrees C by conventional hot air or vacuum drying. Drying characteristics and changes in contents of moisture, anthocyanin, total phenolics, vitamin C, and antioxidant activity in the blueberries during drying were investigated. The effects of PEF-pretreatment on drying efficiency and nutritive quality of blueberries were dependent on drying methods and temperatures. The PEF-pretreatment before vacuum drying significantly (p<.05) reduced the drying time of blueberry samples, from 6 to 4 hr, 10 to 7 hr, and 70 to 40 hr at 75, 60, and 45 degrees C, respectively. The PEF-pretreatment did not significantly (p>.05) influence the retention of nutritional values before drying and also had the least impact on the nutritive quality of dried samples during vacuum drying at 75 degrees C as compared with controls. The Weibull model fitted the drying data of blueberries well. Practical applicationsDrying or dehydration is a popular method to preserve fruits, but it is a time consuming process and could cause the loss of quality and nutritive values. In this study, fresh blueberries were pretreated with pulsed electric fields (PEF) and then dried. The PEF pretreatment significantly increased the drying efficiency, reducing the drying time by 2-30 hr, and did not significantly influence on the nutritive quality. The PEF pretreatment could save production cost significantly by saving labor and energy while it would affect the nutritive quality of dried blueberries. Therefore, PEF pretreatment has great potential for industrial applications.