Construction of starch-sodium alginate interpenetrating network as an effective strategy to improve the quality of extruded whole buckwheat noodles during reheating and soaking periods

In this study, extruded whole buckwheat noodles were prepared by establishing a starch-sodium alginate interpenetrating network reinforcement system. The impacts of reheating methods and soaking time on the structural and quality characteristics of the noodles were also systematically explored. Compared with immersion in boiling water and steaming with boiling water, microwave reheating with boiling water had the shortest reheating time (2.33 min), yet the highest reheating loss (6.94 %) and soup turbidity (3.23 NTU). SEM results indicated that the noodles reheated by microwave with boiling water had the highest porosity (57.32 %) and the lowest number of knots (423). The hardness, tensile force and elongation at break of the noodles after immersion in boiling water were the highest, reaching 51.52 N, 0.131 N and 90.3 % respectively. Additionally, the noodles reheated by microwave with boiling water obtained the highest pGI value of 71.98. After steaming with boiling water to the optimal steaming time and then continuing to soak for 30 min, the interpenetrating gel network maintained a relatively good network state, and the reheating loss only increased from 5.44 % to 9.44 %. During in vitro digestion, its pGI value slowly increased to 83.98, which was much lower than that of wheat noodles (92.20). Compared with boiling water-microwave reheating, boiling water immersion required a longer reheating time but had lower reheating loss and more stable noodle structure. Whereas boiling water steaming balances reheating time and loss. Overall, each reheating method had its pros and cons, and all exerted significant impacts on buckwheat noodle quality.