Physical Properties of Yukwa Base According to the Extrusion Processing Conditions (Ⅰ): Manufacturing of Yukwa Base with Combination of Glutinous Rice Flour and Rice Flour

Abstract

Physical properties of Yukwa base extruded with glutinous rice flour, rice flour, defatted soy flour, and salt using an twin-screw extruder were investigated. The ingredients were extruded at various moisture contents (16~18%), screw speeds (300 & 400 rpm) at 43.4 kg/hr feed rate. Length and specific volume of Yukwa base increased with decreasing moisture contents. Hunter's color L * values of Yukwa base was higher whereas a * and b * values were lower with increasing moisture content. Water absorption index of Yukwa base increased with increasing moisture contents. X-ray diffraction of Yukwa base showed B type moisture content of 16% and 17% while it showed A type moisture content of 18%. Degree of crystallinity and breaking strength of Yukwa base were the lowest in the moisture content of 16% while the lowest value for hardness was found in the moisture content of 16% and of 17% with screw speed 400 rpm for all samples. In the microstructure of cross section of Yukwa base, air cell size was larger and cell wall was thicker as moisture content increased. The sensory evaluation of the Yukwa base showed that color and flavor were not significantly different among samples, while taste, appearance, mouth feel, and overall preference were higher as moisture contents decreased.

Effects of Waxy Rice Moisture Content and Rate of CO2 Injection on Characteristics of Extruded Pellets and Vacuum‐Puffed Yukwa (a Korean Traditional Snack)

“…Additionally, Kim and Ryu (2001) reported that with extrusion conditions of 20-27% moisture content, 2.76 MPa CO 2 gas injection pressure, and 200 rpm screw speed, yukwa puffed by the microwave oven method had low density and soft texture. Eun et al (2009) investigated yukwa extruded with glutinous rice flour, rice flour, defatted soy flour, and salt using a twin-screw extruder, finding that feed moisture content had a significant influence on the physical properties of yukwa bases. Lee et al (2007) concluded that extrusion puffing technology could be adopted as an alternative to conventional deep-fat frying as a partial manufacturing process of yukwa.…”