Rheological properties of sweet potato starch-date syrup gel

Abstract Date syrup (DS), sugars (SG) and sweet potato starch (SPS) composites were investigated using dynamic rheometry, rapid visco-amylograph (RVA), and texture analysis (TPA). HPLC analysis revealed that DS sugar composition was 55% glucose and 45% fructose. Starch gels (0% to 50% DS or SG) were precooked in RVA. SPS starch gel is considered elastic because the elastic modulus (G`) was much greater than the viscous modulus (G``). The comparison between the effect of DS versus SG revealed differences on the peak viscosity, setback, G` and G``, complex viscosity (η*), tan δ, and gel hardness. The decline in complex viscosity (η*) indicates shear thinning behavior. Despite the similarity in sugar content between DS and SG, as shown by the HPLC analysis, the data presented here disclosed how DS had more impact on the pasting and rheological properties of sweet potato starch compared to SG.摘要 本研究采用动态流变测试法、快速黏度分析仪（rapid visco-amylograph, RVA）以及质构分析（texture analysis, TPA），对枣糖浆（Date syrup, DS）、糖（sugars, SG）与甘薯淀粉（sweet potato starch, SPS）的复合体系开展了研究。经高效液相色谱（HPLC）分析可知，枣糖浆的糖组成为55%葡萄糖与45%果糖。将DS或SG添加量为0%至50%的淀粉凝胶置于快速黏度分析仪中完成预煮处理。甘薯淀粉凝胶具备弹性特征，这是由于其弹性模量（elastic modulus, G`）远高于粘性模量（viscous modulus, G``）。对比DS与SG的作用效果发现，二者在峰值黏度、回凝值、G`与G``、复合黏度（complex viscosity, η*）、损耗正切tan δ以及凝胶硬度等指标上均存在显著差异。复合黏度（η*）的降低表明该体系表现出剪切稀化行为。尽管经高效液相色谱分析证实DS与SG的糖含量相近，但本研究数据揭示，相较于SG，枣糖浆对甘薯淀粉的糊化特性与流变特性具有更为显著的影响。