The present study was performed to determine optimum manufacturing condition for maintenance of rheological properties and retrogradation retardation of Korean rice cake, Garaedduk during shelf-life. We investigated the effect of added moisture volume and physical punching process on several rheological properties of Garaedduk. Garaedduk prepared with non-waxy rice, salt, wheat starch and 24% of water (w/w of swelling rice) was stored at 20℃ for 48 h. In order to determine optimum moisture content and punching time, chemorheological and the related quality property changes were analyzed. In this study, we conducted various trials to investigate optimum condition under the five different experimental conditions prepared with manufacturing process determined by our pilot experiments. At results, the key of optimum manufacturing condition for Not-Harden Garaedduk during shelf-life is not one factor but interaction among moisture content, temperature, punching time, and grain starch property. Further study on the mechanism of retrogradation-retardation of Not-Harden Garaedduk is now in progress.Keywords: retrogradation, non-waxy rice, Korean rice cake, Garaedduk, shelf-life *To whom correspondence should be addressed. E-mail: hgjaz@korea.kr
IntroductionIn Northeast Asian countries, such as Korea, Japan and China, rice has been the staple food for most people and a characteristic food ingredient in local traditions including ancestral rites, religious ceremonies, folk customs, agricultural rituals, and seasonal observances. Garaedduk, a class of Korean rice cake, is a food made with rice as the main ingredient. They are named according to how they are made or what is used as the main ingredient (Yoon, 1996). For Korean rice cake rice flour is moistened, heated, and kneaded with physical force. In order for rice-based processed foods to be recognized as more effective and safer sources of carbohydrates in the process of distribution, inhibiting the deterioration of texture by starch retrogradation can be said to be an indispensable key to solving the problems of rice processing (Jiang et al., 2011). Cooked starchy foods have a short shelf life as a result of retrogradation , Hosney, 1986. It is therefore important to develop production technology that helps maintain their texture as it was right after production by controlling the retrogradation process (Juliano, 1985). Factors that are known to influence retrogradation include temperature, moisture, pH, and the molecular structure of starch. Starch retrogradation is less likely to occur at temperatures of more than 60℃, but more likely to take place under lowtemperature conditions unless frozen (Arisaka et al., 1991). Retrogradation proceeds fastest at about 2 − 4℃ but does not occur under dry conditions in which the moisture content is 10 − 15 percent (Lee, 2003). Starches are most prone to retrogradation when they have a moisture content of 30-60 percent, while the phenomenon is delayed at higher moisture contents and seldom occurs under alkaline conditions (pH > 1...