Effect of processing temperature on morphology, crystallinity, functional properties, and in vitro digestibility of extruded corn and potato starches

Native and extruded corn and potato starches were evaluated for microstructure, functional characteristics, and in vitro digestibility. Extrusion treatments were carried out at temperatures of 100, 130, and 160°C with a screw speed of 100 rpm and a feed moisture of 18% using a twin-screw extruder. Starch extrudates revealed lower L* values than native starches. The L*, a*, and b* values of extruded starches decreased with the increase in the extrusion temperature. Extrusion cooking reduced the crystallinity and altered the starch structure. Extruded starches showed higher water solubility index (WSI) and in vitro digestibility with lower water absorption index (WAI) and paste viscosities than native starches. All starches extruded at higher temperatures revealed higher WSI and in vitro digestibility and lower WAI and paste viscosities than those extruded at lower temperatures. The twin-screw extrusion process could be adopted to modify native corn and potato starches for the development of new products with favored characteristics. Practical applications Native starches have some shortcomings that reduce its application in the food industry. In the present research, we investigated the possibility of utilizing a twin-screw extruder to modify native corn and potato starches for the development of products with favored properties. Starches extruded at higher temperatures presented lower breakdown viscosity offering the opportunity to apply in higher thermal stability products. Extrusion cooking significantly increased the in vitro digestibility that could be used in the development of easily digestible food products. Products with dark color may be utilized in the confectionery industry.