The Effect of Blanching on the Quality of Freeze-Dried Edamame

Abstract

Edamame (Glycine max. L. Merill) has been consumed due to its savory taste and high nutrient content. The Edamame can be dried and consumed as a crunchy snack through the freeze-drying process. However, this drying method has its drawbacks, such as a decrease in shrinkage ratio. One of the solutions to this is by blanching treatment before the freeze-drying process. This study aimed to investigate the effect of blanching pre-treatment on the quality of freeze-dried edamame. The properties assessed include moisture content, color, texture, shrinkage ratio, protein content, chlorophyll content, and morphology examination. Fresh edamame with the initial moisture content of 70% w.b. was introduced to the variation of steam-blanching and water-blanching before the freeze-drying process. Each blanching was done for 3, 9, and 15 minutes. The laboratory freeze-dryer used in this study was constructed with a stainless-steel plate (3 mm thickness) and had total dimensions of 1.0 x 0.8 x 1.0 m. The blanching treatment was proven to help promote the product quality, such as a higher shrinkage ratio (p < 0.05) and retain protein and chlorophyll content during the drying process. Hot-water blanching treatment was justified to be better than steam blanching treatment, gave the lowest final moisture content ranged from 3 – 6% d.b. Hot-water blanching also gave better results in terms of textural analysis and chlorophyll retention. The consumer acceptance test showed that freeze-dried edamame with hot-water blanching treatment gave a higher mean liking score than that with steam blanching treatment.