| Summary: | 碩士 === 國立屏東科技大學 === 食品科學系所 === 98 === Rice is one of the important domestic agricultural products, and has been a staple food for a long time. Sweet potato (Ipomoea batatas Lam.) leaf is one of the non-expensive domestic vegetables, and is rich in antioxidant such as polyphenol. In this research, rice and sweet potato leaf were used as raw materials to produce expanded snack food with an indigenous collet extruder by the response surface methodology. Effects of extrusion process variables, i.e., content screw speed (180, 250, 320 rpm), feed moisture content (12, 15, 18%) and sweet potato leaf content (2, 5, 8%), on physical properties (radial expansion ratio, moisture content, water absorption index, water solubility index, bulk density, L value and maximum shear force) and chemical properties (total phenol content, DPPH free radical scavenging ability and reducing power) of extrudates were specifically investigated in this research. The results showed that the highest radial expansion ratio (2.77) and L value (66.20) of extrudates occurred at 250 rpm screw speed and sweet potato leaf content 2% on feed moisture content 12%. At 18% feed moisture content, ext-
rudates exhibited the highest bulk density (0.26 g/cm3). The extrudates had the highest water absorption index (6.35 g/g) and maximum shear force (3.88 Kgf) at screw speed 250 rpm, feed moisture content 18%, sweet potato leaf content 8%. At screw speed 180 rpm, feed moisture content 15%, sweet potato leaf content 2%, extrudates exhibited the highest water solubility index (28.38%). On chemical properties, with sweet potato leaf content increase, total phenol content, DPPH free radical scavenging ability and reducing power were all increased. According to individually response, overall radial expansion ratio, bulk density, water solubility index and total phenol content evaluation on rice-sweet potato leaf extrudates optimum operation condition. At screw speed 256 rpm, feed moisture content 13.13%, sweet potato leaf content 5% were the rice-sweet potato leaf expanded snack food optimum operation condition.
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