化工澱粉糊化液の流動特性のずり応力依存性 <技術報告>

Flow properties of gelatinized modified starch suspensions were studied using a tube viscometer. The modified starches used were commercially available samples of hydroxypropylated distarch phosphate derived from waxy corn and potato starches (Starch A and Starch B). Two types of irreversible shear stress dependence of flow behavior were observed. By applying shear stress on the gelatinized starch suspensions, fluidity of Starch A (5.0 wt%) decreased to an equilibrium value, while fluidity of Starch B (4.5 wt%) increased. The equilibrium fluidities of Starch A depended on the intensity and frequency of the shear stress applied. On the other hand, the equilibrium value for the increase in fluidity of Starch B was not observed. Flow behavior observed under shear stress was not recovered, irrespective of the intensity of shear stress and/or standing period of time.由来澱粉種, リン酸架橋度, 置換度や濃度の異なる化工澱粉糊化液の流動挙動を調べたところ, ヒステリシスに加えて, ずり応力に依存した2種類の流動挙動があることを認めた. この流動は, ワキシーコーンターチ由来のスターチAでは, 負荷したずり応力の大きさや回数に依存して流速が減少し平衡値に達した. また逆に, バレイショ由来のスターチBでは, ずり応力に依存して流速は増加する挙動となった. また, スターチBの流速増加挙動は, 流速が平衡値に達さないで進行し続けた. この両挙動は, ずり応力の大きさや静置時間に関係なく回復しなかった