In vitro digestibility of starch and lipid in noodles as affected by hydrocolloids

Abstract

Part 1. The effects of hydrocolloid type (guar gum, sodium alginate, xanthan gum) and addition levels (0%, 2%, 4%) on the retardation of in vitro starch digestibility were investigated in noodles made by various cereal flours (wheat, whole wheat, buckwheat) with different original glycemic index (GI) and their cooking and textural qualities were evaluated. The pGI of noodles made by wheat or whole wheat flour was significantly decreased by adding hydrocolloids. However, the pGI of buckwheat flour-based noodles with hydrocolloids was slightly increased. Nonetheless, adding hydrocolloids in all noodles positively modified cooking quality regardless of flour type. The hydrocolloids addition in wheat flour-based noodles produced noodles with improved cooking quality and a texture similar to control noodle while still providing reduced starch hydrolysis and pGI. Thus, the nature of flours, the levels and type of hydrocolloids, and their appropriate combination can be used to control in vitro starch digestibility and noodle quality.

Part 2. HPMC (hydroxypropyl methylcellulose) with different degree of substitution (DS) and viscosity were characterized and their effects on the reduction of lipid digestibility and oil uptake in instant fried noodles were investigated. To produce an instant fried noodle, wheat flour, salt and various cellulose derivatives containing cellulose, carboxymethyl cellulose (CMC), HPMC were mixed with water. Results showed that the addition of HPMC retarded the lipid digestibility significantly (p<0.05). The oil uptake and lipid digestibility decreased with decreasing the degree of substitution (DS) and increasing viscosity of HPMC. Furthermore, at same apparent viscosity, the oil uptake and lipid digestibility decreased with increasing viscosity of HPMC. This result may be because lipid digestibility was affected by other factors as well as DS and viscosity. Moreover, the optimum cooking time and breaking stress of instant fried noodles increased with high apparent viscosity HPMC. Therefore, it showed that HPMC had positive effects on the property attributes of instant fried noodles. Thus, the replacement of HPMC for wheat flour in instant fried noodles provided health benefit such as reduction of oil uptake and lipid digestibility.