Effect of Thermostable α-Amylase Addition on Producing the Porous-Structured Noodles Using Extrusion Treatment

Problems with rehydration and palatability are considered as unacceptable quality characteristics for the noodles produced using high-strength extrusion technique. Thus, the aim of this study was to solve these problems by designing a novel method to create a porous structure for the high-strength extruded noodles (HENs). The quality indices of HENs were significantly improved after adding to them thermostable α-amylase (TαA) at 0.05% to 0.10%. The microstructure graphs showed that a well-developed porous structures was successfully created throughout noodle strands. This indicated that the TαA has effectively worked on starch granules in spite of the high-strength performance of the extrusion process. MALLS-GFC, X-ray diffraction, and differential scanning calorimeter investigations showed that the appearance of a porous structure was mainly attributed to the internal collapse of α-1,4-glycosidic bonds and the dissolution of water-soluble degradation products, such as dextrin and oligosaccharides. Moreover, the slight inhibited effect of excess TαA on the starch gelatinization was because of the fact that the high enzyme concentration might cause TαA to adhere or overlay on it.

The rehydration and palatability properties of HENs were greatly improved by creating a well-developed or honeycomb-like porous structure using TαA at low concentration. The findings of this study could be applied to enhance the quality characteristics of HENs and to encourage the research and development in the noodle industry.