Kim Sung-Gun, Yoo Whachun, Yoo Byoungseung
Department of Food Science and Technology, Dongguk University, Seoul 100-715, Korea.
Rheosfood Inc., Seoul 100-715, Korea.
Prev Nutr Food Sci. 2014 Sep;19(3):242-5. doi: 10.3746/pnf.2014.19.3.242.
The flow behaviors of three thickened fruit juices (orange, apple, and grape juice) prepared with a commercial instant xanthan gum (XG)-based thickener that is marketed in Korea were investigated at different thickener concentrations (1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 3.5%) and setting times (5 and 30 min) using a rheometer and a line-spread measurement method. The flow distance values measured by the line-spread test (LST) were compared with the apparent viscosity (ηa,50) values measured with a sophisticated computer-controlled rheometer. The ηa,50 values of the juices increased as thickener concentration increased, whereas their flow distances decreased. The ηa,50 values at the 30-min setting time were much higher than those at the 5-min setting time, indicating that the setting time before serving or consuming thickened juices can affect viscosity values. Plots comparing ηa,50 values to LST flow distances revealed strong exponential relationships between the two measures (R(2)=0.989 and R(2)=0.987 for the 5- and 30-min setting times, respectively). These results indicate that the LST can be a suitable instrument for evaluating the viscosity of thickened fruit juices prepared with different XG-based thickener concentrations and setting times for the dysphagia diet.
使用流变仪和线扩展测量方法，研究了在韩国市场销售的一种基于商业即食黄原胶（XG）的增稠剂制备的三种浓缩果汁（橙汁、苹果汁和葡萄汁）在不同增稠剂浓度（1.0%、1.5%、2.0%、2.5%、3.0%和3.5%）和凝固时间（5分钟和30分钟）下的流动行为。将通过线扩展试验（LST）测量的流动距离值与使用精密计算机控制流变仪测量的表观粘度（ηa,50）值进行比较。随着增稠剂浓度的增加，果汁的ηa,50值增加，而其流动距离减小。30分钟凝固时间下的ηa,50值远高于5分钟凝固时间下的ηa,50值，这表明在供应或饮用浓缩果汁之前的凝固时间会影响粘度值。比较ηa,50值与LST流动距离的图表显示，这两种测量方法之间存在很强的指数关系（5分钟和30分钟凝固时间的R(2)分别为0.989和0.987）。这些结果表明，LST可以作为一种合适的仪器，用于评估用不同基于XG的增稠剂浓度和凝固时间制备的浓缩果汁对吞咽困难饮食的粘度。
