Antistaling effect of raw barley flour in rice starch gel and Korean rice cake under Retrogradation Retardation Technology

Abstract

The antistaling effect of raw barley flour substitute for raw wheat flour under retrogradation-retardation technology (RRT) was investigated in rice starch gel and garaedduk. The crude enzyme extracts from wheat and barley flour were showed 31.89 and 17.61 BU/g β-amylase activities respectively, while the α-amylase activities were hardly appeared. Thus, raw wheat and barley flour of 0.70% and 1.27% were added into rice starch gel and garaedduk under RRT on the basis of the β-amylase activity. In both rice starch gel and garaedduk, the treatment of raw wheat flour maintained gel strength and garaedduk hardness during storage at 4℃. However, adding raw barley flour exhibited the significant decrease in gel strength and garaedduk hardness during storage (p<0.05). Specially, raw barley flour treated-garaedduk showed collapsed structure after 7 storage days. Enthalpy change did not detected in the rice starch gel and garaedduk treated with both flours, indicating that both flours affected antistaling to gel and garaedduk. In addition, the increased degree of hydrolysis of both samples during storage supported that the enzymatic hydrolysis from both flours could play an important role in retrogradation retardation. As a result, raw barley flour could be replaced for raw wheat flour in garaedduk preparation under RRT, while it needs to be considered sticky texture after storage.|Retrogradation-retardation technology (RRT) is making process that is delayed retrogradation of garaedduk during storage. Our previous study confirmed that raw barley flour could be substituted for wheat flour under RRT as a cereal amylase. However, raw barley flour treated-garaedduk had undesirable texture such as collapsed and sticky structure after 7 day storage. Thus, this study was focused on improving the texture of raw barley flour treated-garaedduk by application of re-steaming process for controlling enzymatic hydrolysis. Rice starch gel model was used to analyze the gel strength change by various incubation time after adding barley flour and internal gel temperature after re-steaming. As incubation time increased, gel strength change was decreased, and as internal gel temperature lowered after re-steaming, the gel strength change was decreased during 12 days storage. Among these conditions, the re-steaming process of 3h-55℃ was selected for garaedduk preparation because gel strength was maintained for 1-12 days storage at 4℃ (p<0.05). Garaedduk sample prepared under the re-steaming process exhibited neither retrogradation nor sticky texture during storage for 12 days.; Retrogradation-retardation technology (RRT) is making process that is delayed retrogradation of garaedduk during storage. Our previous study confirmed that raw barley flour could be substituted for wheat flour under RRT as a cereal amylase. However, raw barley flour treated-garaedduk had undesirable texture such as collapsed and sticky structure after 7 day storage. Thus, this study was focused on improving the texture of raw barley flour treated-garaedduk by application of re-steaming process for controlling enzymatic hydrolysis. Rice starch gel model was used to analyze the gel strength change by various incubation time after adding barley flour and internal gel temperature after re-steaming. As incubation time increased, gel strength change was decreased, and as internal gel temperature lowered after re-steaming, the gel strength change was decreased during 12 days storage. Among these conditions, the re-steaming process of 3h-55℃ was selected for garaedduk preparation because gel strength was maintained for 1-12 days storage at 4℃ (p<0.05). Garaedduk sample prepared under the re-steaming process exhibited neither retrogradation nor sticky texture during storage for 12 days.