Rheological Characteristics of Gelatinized Dispersions and Pasting Properties of Sereral Starches

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  • 各種デンプン糊化液のレオロジー的特性と糊化特性について
  • カクシュ デンプン コカエキ ノ レオロジーテキ トクセイ ト コカ トクセイ ニ ツイテ

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Abstract

It is well known that there are great differences among the flowcharacteristics of non-Newtonian fluids such as gelatinized starchdispersions depending on the analytical devices used. So, this paper mainlyinvestigated the rheological characteristics of starches from potato, sweetpotato, corn, wheat and commercial thickening agents for baby foods("Product A") and for aged persons with difficulty of chewing and/orswallowing ("Product B"). We used rheological instruments in our laboratoryin addition to optical and scanning electron microscopic observations of thestarch granules and time-dependant temperature declines of gelatinizedstarch dispersions. Microscopic observations showed similar size and shape of each sample tothose reported previously, while there were no starch granules in Product Aor B, which seemed to be pre-gelatinized starch products. The potato starch and Product A exhibited excellent temperature holdingeffects, while those of corn and wheat starches were inferior. Since Product B began to partly gel during measurement with a rotationalviscometer (TVC-5, Toki Sangyo Co., Ltd. ), the apparent viscosity was notstable, but on average the value was the highest of all, followed by potatostarch. The apparent viscosities of corn and wheat starches and Product Awere low. The apparent viscosities of the samples examined were mostlyconstant over the period of time to which those were subjected to shearingstress. Although the viscosity characteristics obtained with a vibrationviscometer SV-10 (A&D Co., Ltd.) were similar to those of the rotationalviscometer, the viscosity values in themselves were 1/5 to 1/10 of TVC-5. It seemed that a hot-wire viscosity sensor Rheocatch SVM-10 (Snow BrandMilk Products Co., Ltd.), where the heat transfer coefficient change due toviscosity fluctuation was monitored, could be applied to assessing thegelatinization temperature of a starch.

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