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

¹Department of Food Science and Technology, Kongju National University, Chungnam 340-802, South Korea. ²Corresponding author. Phone: +82-41-330-1484. Fax: +82-41-335-5944. E-mail: ghryu@kongju.ac.kr

Extrusion with CO₂ injection was developed to simplify the process of producing vacuum-puffed yukwa (rice snacks). The effects of feed moisture content and CO₂ injection on the characteristics of extruded pellets (maximum viscosity and degree of gelatinization) and vacuum-puffed yukwa (expansion ratio, bulk density, hardness, and color) were investigated. Higher feed moisture increased the size of vacuum-puffed yukwa and the degree of gelatinization, whereas the maximum viscosity decreased. Maximum viscosity and gelatinization degree of extruded pellets were highly correlated with expansion ratio, bulk density, hardness, and color values of vacuum-puffed yukwa. Increasing feed moisture content significantly increased expansion ratio but decreased bulk density and hardness. CO₂ injection decreased bulk density and hardness of vacuum-puffed yukwa.