It is well known that there are great differences among the flow characteristics of a non- Newtonian fluid such as gelatinized starch dispersions, depending on the analytical devices used and measurement conditions. So, this paper mainly investigated the rheological characteristics of starches from potato, sweet potato, corn, wheat and commercial thickening agents for baby foods ("Product A") and for aged persons with difficulty of chewing and/or swallowing ("Product B"). We used rheological instruments in our laboratory in addition to optical and scanning electron microscopic observations of the starch granules and time-dependant temperature declines of gelatinized starch dispersions. Microscopic observations showed similar size and shape of each sample to those reported previously, while there were no starch granules in Product A or B, which seemed to be pregelatinized starch products. The potato starch and Product B exhibited excellent temperature holding effects, while those of corn and wheat starches were inferior. Since Product B began to partly gel during measurement with a rotational viscometer (TVC-, Toki Sangyo Co., Ltd. ), the apparent viscosity was not stable, but on average the value was the highest of all, followed by potato starch. The apparent viscosities of corn and wheat starches and Product A were low. The apparent viscosities of the samples examined were mostly constant over the period of time when those were subjected to shearing stress. Although the viscosity characteristics obtained with a vibration viscometer SV-1 (A&D Co., Ltd.) were similar to those of the rotational viscometer, the viscosity values in themselves were 1/ to 1/1 of TVC-. It seemed that a hot-wire viscosity sensor Rheocatch SVM-1 (Snow Brand Milk Products Co., Ltd.), where the heat transfer coefficient change due to viscosity fluctuation was monitored, could be applied to assessing the gelatinization temperature of a starch. * 宮城学院女子大学食品栄養学科
y n y n y n Δt
表 1. 各種デンプン糊化液の温度低下時間 ( 室温放置 ) デンプン試料 3 に達する ジャガイモサツマイモトウモロコシコムギ市販増粘剤 A 市販増粘剤 B 148 142 114 128 146 194 表 2. 各種デンプン糊化液の温度低下時間 ( 恒温槽放置 ) デンプン試料 3 に達する ジャガイモサツマイモトウモロコシコムギ市販増粘剤 A 市販増粘剤 B 36 36 18 14 26 6 表 3. 各種デンプンの糊化温度 デンプン試料加熱 糊化 ジャガイモ (%) サツマイモ (%) トウモロコシ (%) コムギ (1%) 27. 3.6 7.8 49.8 66. 74.4 87.3 84.9
ジャガイモ サツマイモ トウモロコシ コムギ 増粘剤 A 増粘剤 B ジャガイモ サツマイモ トウモロコシ コムギ 増粘剤 A 増粘剤 B
1 9 8 7 6 4 ジャガイモサツマイモトウモロコシコムギ増粘剤 A 増粘剤 B 3 2 1 7 1 1 1 17 2 1 9 8 7 6 4 ジャガイモサツマイモトウモロコシコムギ増粘剤 A 増粘剤 B 3 2 1 1 1 2 3 3 4 4 6
粘度 (mpa s) 6 4 4 3 3 2 1 1 1 1 2 3 3 4 ジャガイモ (3%) サツマイモ (%) トウモロコシ (7.%) コムギ (7.%) 増粘剤 A 増粘剤 B 粘度 (mpa s) 1 9 8 7 6 4 3 ジャガイモサツマイモトウモロコシコムギ増粘剤 A 増粘剤 B 2 1 2 4 6 8 1 12 14 16 18
1 9 8 7 6 4 3 2 1 4 3 3 2 1 1 センサー A センサー B 1 2 3 4 6 7 8 1 9 8 7 6 4 3 2 1 1 2 3 4 6 7 8 4 3 3 2 1 1 1 9 8 7 6 4 3 2 1 1 b) 2 3 4 6 7 8 4 3 3 2 1 1 1 9 8 7 6 4 3 2 1 1 c) 2 SesA SesB d()/dt 3 4 6 7 8 4 36 32 28 24 2 16 12 8 4-4 d)
1 9 8 7 6 4 3 2 1 1 2 3 4 6 7 8 4 3 3 2 1 1 1 9 8 7 6 4 3 2 1 b) 1 2 SesA 3 4 SesB d()/dt 6 7 8 4 36 32 28 24 2 16 12 8 4-4 1 9 8 7 6 4 3 2 1 1 2 3 4 6 7 8 4 3 3 2 1 1 1 9 8 7 6 4 3 2 1 b) SesA d()/dt 1 2 3 4 SesB 6 7 8 4 36 32 28 24 2 16 12 8 4-4
1 9 8 7 6 4 3 2 1 1 2 3 4 6 7 8 4 3 3 2 1 1 1 9 8 7 6 4 3 2 1 b) 1 SesA d()/dt 2 3 4 SesB 6 7 8 4 36 32 28 24 2 16 12 8 4-4 1 9 8 7 6 4 3 2 1 c ) 1 2 3 4 6 7 8 4 3 3 2 1 1 d) 1 9 8 7 6 4 3 2 1 1 2 3 4 6 7 8 4 3 3 2 1 1 1 9 8 7 6 4 3 2 1 1 b) 2 3 4 6 7 8 4 3 3 2 1 1
1 9 8 7 6 4 3 2 1 1 2 3 4 6 7 8 4 3 3 2 1 1 1 9 8 7 6 4 3 2 1 1 b) 2 3 4 6 7 8 4 3 3 2 1 1 1 9 8 7 6 4 3 2 1 1 2 3 4 6 7 8 水ジャガイモサツマイモトウモロコシコムギ 1 9 8 7 6 4 3 2 1 b) 1 2 3 4 6 7 8 水ジャガイモサツマイモトウモロコシコムギ