化工澱粉糊化粒子の膨潤に及ぼすずり応力の影響 <技術論文>

Effect of Cross-linking Levels and Starch Concentration on Shear-dependent Flow Properties of Gelatinized Modified Starch Suspension

朝田 仁

鈴木 寛一

日本食品科学工学会誌

Cross-linked starch suspensions sheared at various shear stresses showed two types of flow behavior. One type indicates a behavior of increasing fluidity, which is observed in concentrated suspensions of weakly cross-linked starch. Although sheared granules are smaller than non-sheared granules, the increasing fluidity of cross-linked starch suspensions is explained by the rupture of fully swollen starch granules. As the swollen granules rupture, the flocculation network of the granules decreases, resulting in a decrease in the viscosity and an increase in the fluidity of starch suspensions. Another flow behavior is decreasing fluidity, which is observed in highly cross-linked starch. The decreasing fluidity of cross-linked starch suspensions results from the re-swelling of granules from the application of unheated shear stress. The re-swollen granules enlarge with strong flocculation, resulting in a decrease of fluidity. Hence, the disruption or the re-swelling of sheared granules explains the two types of fluidity observed in cross-linked starch suspensions. A combination of cross-linking level and starch concentration determines the fluidity type of gelatinized suspensions.

化工澱粉糊化液にずり応力を負荷すると, ずり応力に依存して流動性が増加あるいは減少する流動挙動が確認された. この原因を化工澱粉の糊化とずり応力負荷に伴う澱粉粒子の膨潤の面から考察するために, 市販のリン酸架橋度の異なる化工澱粉を使用し, これらの糊化液の濃度やずり応力負荷時の流動性, みかけ粘度, 糊化澱粉粒子径, 粒度分布を測定した.

ずり応力負荷によって糊化液の流動性が増加する挙動は, 負荷ずり応力によって膨潤澱粉粒子が崩壊して, 糊化澱粉粒子径が小さくなることで, みかけ粘度が低下することが確認された. この澱粉粒子が負荷ずり応力で崩壊する現象は, 低リン酸架橋度で高濃度の糊化液で見られた. 逆に, 流動性が減少する挙動は, 負荷ずり応力の増加に伴って糊化粒子が再膨潤して粒子径が増大することで, みかけ粘度が発現して起こった. この流動性減少挙動は, 高リン酸架橋の高濃度糊化液で認められた.

modified starch

gelatinization

shear stress

fluidity

rheology

化工澱粉

膨潤

ずり応力

流動性

食品レオロジー

家政学・生活科学 [ 590 ]

日本語

日本食品科学工学会

[ISSN] 1341-027X

[DOI] 10.3136/nskkk.54.222

[NCID] AN10467499

[DOI] http://dx.doi.org/10.3136/nskkk.54.222