Investigation of freezing temperature and time to improve resistant starch content and quality of pure mung bean starch vermicelli

Abstract

Mung bean vermicelli is one of the commonly consumed styles of noodles because of its convenience in Asian countries as well as being a good source of resistant starch (RS). It was hypothesized that suitable freezing conditions could produce mung bean vermicelli with a greater RS content and good cooking quality compared to the commercially available product. Therefore, this study investigated the optimum freezing conditions to increase the RS content in mung bean vermicelli. After extrusion, boiling, and cooling, the drained vermicelli was incubated at 4 C for 1 h 30 min before using different freezing conditions by varying the processing temperature (-5, -10, -15, or -20 C) and time (6, 12, 18, or 20 h for each temperature).The highest RS content was observed in dried mung bean vermicelli (12.83% at -10 C for 18 h; V1018), whereas the commercial vermicelli had the lowest RS content (9.73%). The cooking time, water absorption, volume increase, and resistant starch content of cooked V1018 were higher with values of 12.69 min, 502.97%, 19.13% and 7.32%, respectively, than those of the commercial vermicelli (8.56 min, 347.34%, 15.19% and 5.58%, respectively). Furthermore, the cooking loss, tensile strength, and elasticity of V1018 were 1.08%, 0.0101 N, and 11.96 mm, respectively, which were lower than for the commercial vermicelli (1.96%, 1.16-folds, and 2.16-folds, respectively). The color of dried V1018 vermicelli had more lightness, redness, and yellowness, while the cooked V1018 vermicelli had more lightness, greenness, and blueness than the respective commercial products. Hence, incubating at 4 C for 1 h 30 min, followed by freezing at -10 C for 18 h was recommended to produce pure mung bean starch vermicelli with a high resistant starch content and good quality