Effect of Xanthan Gum on the Quality of Syrup Thickened by Modified Starch during Heating and Storage

บทคัดย่อ

In heating during production and in storage, the reduction in the viscosity of fruit syrup stabilized by starch is a problem in the food industry due to starch degradation, especially in low pH systems. The influence of xanthan gum (Xan) on the rheological properties of syrups with different heating times and during storage was investigated. Blueberry syrups were prepared using 4% total concentration of polysaccharides with different mixing ratios of modified tapioca starch (MTS) and Xan (MTS/Xan = 4/ 0, 3.9/0.1, 3.8/0.2 and 3.7/0.3). The syrups were heated to 90°C and further heated for 20, 40, 60 and 80 min. All formulations with different heating times exhibited lower viscosity with shear rate. Viscosities of the syrups containing Xan were higher than those without Xan. The syrup containing 0.2%Xan (MTS/Xan = 3.8/0.2) obtained from heating at 90°C for 40 min was selected to evaluate the quality change during storage according to the highest sensory scores of thickness and overall liking. The syrup with 0.2% Xan substitution for MTS exhibited higher viscosity and a lower rate of viscosity reduction than that without Xan. Zero-order equations were used for shelf life evaluation of the syrups. Overall liking scores of the syrup with 0.2% Xan before and after storage for 16 wk were not significantly
(p>0.05) different and exhibited higher scores than those without Xan. The results suggested that Xan could be used in fruit syrup to enhance quality and stability in terms of viscosity during heating and storage.