Comparative study of the effects of thermal blanching pretreatments and puffing temperature levels on the microstructure and qualities of crisp banana slices

Abstract

Applying a high-temperature and short-time (HTST) puffing techniques is one way to produce fat-free crisp snacks. However, the crisp snack products obtained via HTST tend to be browner with some scorching on their surface but several thermal blanching pretreatments can be used to limit such surface browning.Therefore, in this study, the effects of thermal blanching pretreatments and puffing temperature levels on the microstructure, drying time, and the qualities of crisp banana were investigated. Banana slices (2.5 mm thickness) were blanched by hot water, steam, and microwave pretreatments as well as dried by hot air at temperature of 90 C combined with hot air puffing in temperature ranges 150-190 C. The blanching pretreatments significantly limited browning and improved the uniformity of crisp product color. The hot water or steam pretreatments caused pronounced cells damage and swelling of the cell wall region, whereas the microwave pretreatment may have increased the cell wall strength of banana.Such differences in morphological structure resulted in a larger volume ratio and more crisp texture for the hot water-or steam-pretreated bananas, yet different results were also observed for the microwave-pretreated banana. The longest processing time of 367.0 min was observed on the microwave-pretreated sample coupled with the lowest puffing temperature, 150 C. Therefore, appropriate either a pretreatment with hot water or steam together with puffing temperature of 170 C is recommended for banana processing to make crisps. Practical ApplicationsThe Namwa banana is commonly consumed as a fresh banana but it also rapidly deteriorates after harvesting. Therefore, it has been processed using several drying techniques to extend its shelf life and increase its market value. Novel drying techniques such as high-temperature and short-time (HTST) puffing could produce fat-free crisp snack, especially given that this economical drying process and simple drying equipment required are well suited to small-and medium-manufacturing enterprises. Nevertheless, via HTST, the crisp banana product undergoes more intensive browning and becomes nonuniform in color. Thermal blanching pretreatments are also required for banana processing because these could limit the browning and improved the uniformity of crisp