Effects of hot-air microwave rolling blanching pretreatment on the drying of turmeric (Curcuma longa L.): Physiochemical properties and microstructure evaluation.

Blanching pretreatment can improve product quality and efficiency during food processing. Effects of hot-air microwave rolling blanching (HMRB) on physiochemical properties and microstructure of turmeric were investigated under various treatment times (0-10 min). Results showed that HMRB significantly changed weight, electrolyte leakage, texture, viscoelastic properties, pectin fractions content, thermal properties and drying quality of turmeric. Meanwhile, HMRB promoted the redistribution of water in turmeric and changed the cell structure, thus shortening drying time by 6.35-34.92 %. The polyphenol oxidase and peroxidase were entirely inactivated after blanching for 8 and 10 min, respectively. Compared with unblanched dried turmeric, the curcumin content, total phenolic, DPPH and ABTS were significantly increased by 20.76 %, 5.63 %, 7.54 % and 19.05 % at the optimal blanching time (8 min). Overall, HMRB can be used as a promising pretreatment technology to enhance the drying rate and improve the quality of dried turmeric.

Hot-Air Flow Rolling Dry-Blanching Pretreatment Improves the Drying Quality of Acanthopanax sessiliflorus by Increasing the Drying Rate and Inactivating Enzymes.

The processing of Acanthopanax sessiliflorus has attracted interest due to its health benefits. In this work, an emerging blanching technology, called hot-air flow rolling dry-blanching (HMRDB), was employed to treat A. sessiliflorus before drying. The effects of varied blanching times (2-8 min) on enzyme inactivation, drying characteristics, bioactive compound retention, and microstructure were examined. The results demonstrated that blanching for 8 min rendered polyphenol oxidase and peroxidase nearly inactive. The blanching process reduced the drying time of samples by up to 57.89% compared to an unblanched sample. The Logarithmic model showed good fitting performance for the drying curves. The total phenolic and flavonoid content of the dried product increased as blanching time increased. The total anthocyanin content of the samples blanched for 6 min was 3.9 times higher than that of the unblanched samples, and 8 min of blanching produced the greatest DPPH• and ABTS• scavenging capabilities. The retention of active compounds in a dried product is a result of the inactivation of enzymes and a reduced drying period. Changes in the porous structure of the blanched samples would be responsible for the accelerated drying rate, according to microstructural analysis. These results indicate that HMRDB enhances the drying process and improves drying quality when applied to A. sessiliflorus before drying.

Effect of different drying techniques on drying kinetics, nutritional components, antioxidant capacity, physical properties and microstructure of edamame.

The present study aimed to investigate the effect of hot air drying (HD), microwave rolling-bed drying (MRD), hot air microwave rolling-bed drying (HMRD), pulse-spouted microwave vacuum drying (PSMVD) and freeze-drying (FD) on the drying characteristics, quality properties and microstructure of edamame. Six models were fitted the drying curves, and quality attributes were analyzed. Results indicated that Page model was the most suited model for edamame drying. Compared with HD, MRD and HMRD improved the quality of edamame and decreased the drying time by 45.59% and 36.03% respectively. The FD and PSMVD possessed higher rehydration ability, nutrient retention and antioxidant capacity compared with other methods. Moreover, PSMVD products showed a crunchy texture, the less color change and the shortest drying time (70 min). Microscopy images demonstrated a distinct porous structure in PSMVD, which facilitated the moisture transfer. Overall, PSMVD is a promising dehydration method for obtaining high value-added edamame products.