Application of hsian-tsao leaf gum, xanthan gum and locust bean gum to starch pearl model systems

Abstract

The mixed systems are consisted of 8% tapioca starch and 1% hydrocolloids, hsian-tsao leaf gum(HG)/locust bean gum(LBG) or xanthan gum(XG) both are mixed for 4/0,3/1,2/2,1/3 and 0/4. The effects of hydrocolloids on the gelatinization and gelling behavior of tapioca starch are studied during controlled heating and cooling process using rapid-visco analysis and differential scanning calorimetry. The viscoelasticity and retrogradation of hydrocolloids/tapioca starch mixed systems for after stored 0~7 days are measured by dynamic rheological analysis, and these results compare with commercial dehydrated starch pearls. In addition to take the samples, which were similar with commercial dehydrated starch pearls in viscoelasticity, performed the stored in milk tea test for 4℃ and sensory evaluation. The results of rapid-visco analysis show that addition of hydrocolloids result in gelatinization temperature of tapioca starch increasing. Additionally, LBG and XG make gel viscosity increasing, but viscosity loss decreasing due to thermal resistance increasing. For thermal analysis, addition of hydrocolloids results Tp of tapioca starch increasing significantly. For dynamic rheological analysis, the G' of mixed systems (except for HG/LBG=0/4, HG/XG=0/4) are increasing with HG concentration increased, and the retrogradation index of mixed systems are changed for addition of hydrocolloids. For the stored in milk tea test for 4℃, the sugar in milk tea is decreasing during storage period due to the sugar permeates into the network of gel, so resulting the viscoelasiticy of gels chenged. The retrogradation index of HG/LBG=2/2,1/3,0/4 and HG/XG=1/3 are lower than commercial dehydrated starch pearl. The result of sensory evaluation shows acceptable degree of aroma increasing due to addition of HG. Additionally, for firmness and chewiness, the results of HG/LBG=2/2 and HG/XG=1/3 are higher than commercial dehydrated starch pearl system. Finally, appropriate ratio of HG/LBG and HG/XG may improve the retrodation of starch pearl refrigeration.

本實驗以碳酸氫鈉溶液萃取之仙草葉膠，分別依4/0、3/1、2/2、1/3和0/4五種比例與刺槐豆膠或三仙膠一起添加於樹薯澱粉中，使多醣膠總濃度調整為1%，澱粉濃度為8%，利用快速黏度分析儀與示差熱掃描分析儀，探討水合膠之種類及混合比例對樹薯澱粉糊化及凝膠情形的影響；利用動態流變儀探討水合膠/樹薯澱粉混合凝膠於冷藏0~7天期間的黏彈特性與回凝情形，並與市售乾燥粉圓系統作比較。另外，選擇黏彈性質與市售乾燥粉圓粉末所製備凝膠之黏彈性質較為相近之粉圓模式樣品（即HG/LBG=2/2,1/3,0/4及HG/XG=1/3之組別），進行浸泡於奶茶冷藏之貯存試驗及消費者型官能品評試驗。在快速黏度分析的結果顯示，水合膠的添加會使樹薯澱粉的糊化溫度上升，而刺槐豆膠與三仙膠的添加會使混合系統的凝膠黏度上升，並使黏度損失百分比減少，熱抗性增加。在熱分析方面，水合膠體的添加使樹薯澱粉的糊化尖峰溫度明顯增加。在動態流變分析方面，除HG/LBG=0/4與HG/XG=0/4之組別外，仙草葉膠濃度越高，混合系統之貯存模量值也越高，而回凝指標（Retrogradation index）也會受水合膠的種類及濃度影響。而在奶茶貯藏試驗中，發現奶茶的糖度在貯藏過後會降低，顯示糖在貯藏期間會滲入混合系統的膠體結構中，而影響膠體之黏彈性質。然HG/LBG=2/2,1/3,0/4及HG/XG=1/3之組別，其回凝指標皆明顯較市售乾燥粉圓所製備之凝膠低。在官能品評的結果中，發現在香氣方面，添加仙草葉膠會使消費者的整體喜好程度提高；而在硬度及口感方面，以HG/LBG=2/2或HG/XG=1/3的組別較佳，其平均分數高於以市售乾燥粉圓所製備之凝膠。綜合以上結果，適量HG搭配LBG或XG，或可應用於改善粉圓因冷藏回凝而使質地變硬之現象。