Antistaling effect of wheat flour in retrogradation-retardation technology

Abstract

Part 1 This study focused on the mechanisms of retrogradation-retardation technology for applications in garaedduk (steamed and extruded cylinder-shaped rice cake) production. Based on the comparison of conventional and retrogradation-retardation methods, the addition of raw wheat flour was selected as a key process. The crude amylase activity of crude enzyme extract from wheat flour was measured at various reaction temperatures (20℃, 30℃, 40℃, 50℃, and 60℃). The enzyme activity of wheat flour increased sharply from 20℃ to 40℃ and then decreased dramatically from 40℃ to 60℃, showing maximum activity at 40℃. The rheological properties of gelatinized rice starch pastes after treatment with raw or autoclaved wheat flour and Novamyl L were investigated. Among them, raw wheat flour and Novamyl L resulted in significantly lowered the elastic modulus. The textural properties of garaedduk treated with raw or autoclaved wheat flour were examined by texture profile analysis (TPA) during storage for 3 days at 4℃. The hardness of garaedduk made with raw wheat flour was maintained for up to three days. In contrast, autoclaved wheat flour did not affect the elastic modulus, hardness, or the generation of reducing sugars. As a result, raw wheat flour effectively retard starch retrogradation through starch hydrolysis induced by amylase in wheat flour.

Part 2 The enzymatic reaction in rice starch paste made through retrogradation-retardation technology was investigated by controlling wheat flour reaction conditions. Elastic modulus (G′) in rice starch paste was investigated when wheat flour was added at various reaction temperatures (40℃, 50℃, 60℃, 70℃, and 80℃) and different amounts (0%, 2.5%, 5.0%, 7.5%, and 10%; w/w of rice starch) during incubation (60 min). The hardness of garaedduk prepared by controlling wheat flour adding conditions (various dough temperatures, 45℃, 55℃, and 65℃; different levels of wheat flour, 0.7%, 1.0%, and 1.4% by weight) was analyzed for 2 days at 4℃. The slope of G′ curve in starch paste with 5% wheat flour reduced in order of 50℃ → 60℃ → 40℃, but those at 70-80℃ was maintained during incubation time. On the other hand, G′ curves in starch paste at 60℃ exhibited steeper slope with increasing added wheat flour amounts. After 2 days storage, the hardness of garaedduk by adding temperature of wheat flour was 7,585, 6,319, and 4,874 g at 45℃, 55℃, and 65℃, respectively. Also, the hardness of garaedduk made with different levels of wheat flour was 4,874, 4,596, and 4,279 g for 0.7%, 1.0%, and 1.4%, respectively. However, there was only significant difference in the hardness of garaedduk made with 0.7% and 1.4% of wheat flour. As a result, antistaling effect in retrogradation-retardation technology could be controlled by adjusting wheat flour level at optimum temperature.