Yoshihiro Kohda

Indicative evidence for a conformational transition in ι-carrageenan

Abstract The non-Newtonian behavior and dynamic viscoelasticity of ι-carrageenan solutions were measured with a rheogoniometer. The K salt of ι-carrageenan showed Newtonian behavior 1.5%, whereas the Ca salt of ι-carrageenan showed plastic behavior even at 0.3%. A gelation occurred in polysaccharide concentrations >1.5 and 0.5% for K and Ca salt of ι-carrageenan upon cooling, respectively. The transition temperature, at which dynamic viscoelasticity decreased rapidly, was observed at 45 or 50° at various concentrations of the Ca salt of ι-carrageenan. The dynamic modulus of the Na and K salts forms of ι-carrageenan showed a very high value at low temperature, and increased with an increase in temperature, showing a maximum value at 5°, then it decreased at 0.2% in the presence of CaCl 2 . However, in the presence of KCl, the K salt form of ι-carrageenan showed a very low dynamic modulus upon cooling. The rheological characteristics of the Ca salt of the ι-carrageenan molecule might be essentially attributed to an intramolecular association, contributed by sulfate groups of adjacent 3,6-anhydro- d -galactose and d -galactose residues through Ca 2+ ions with ionic forces.

Relationships between Physical Properties and Chemical Components of Okinawan Brown Sugar

Some physical properties and chemical components of brown sugar produced in Okinawa were investigated to improve the quality standard and manufacturing methods. Hardness, viscosity, color, moisture content, water activity, and density of brown sugar were measured as the components of physical properties. Content of K, P, Ca, Mg, Na, N, and Cl in the brown sugar were measured. As the result of investigation, it became clear that the physical properties of brown sugars varied with the island where the sugar was produced; and P, N, and Ca significantly affected the quality of sugar.

Visco-elastic Behavior of Air classified Wheat Flour Dough

小麦粉の蛋白質含量を変えて用途を拡大する技法の開発の一環として,空気分級をした小麦粉の粘弾性的挙動を求めた。WW種小麦に内麦30%及び10%を加えた粉を,前者については微粉砕したうえで,それぞれ空気分級して蛋白質含量の異なる5画分を作り,加水量が50%になるように水を加えてドウとし,水平振動位相差法で動的粘弾性を求めたところ,振動数の増大に応じて弾性値も増大し粘性値は減少した。また蛋白質含量が増大すると蛋白質含量の高い範囲では蛋白質含量に応じて粘弾性も増大した。蛋白質含量が少ないときに必ずしも蛋白質含量に比例して粘弾性が増大しない理由として,グリアジンとグルテニンの含量配分の差を生じたか,またグルテンの網目形成に関する脂質の影響の可能性を検討したが,いずれからも明確な結論を得られなかった。空気分級で蛋白質含量を増大させた場合とグルテンを加えて蛋白質含量を増大させた場合の効果を比較したところ,同じ蛋白質含量では空気分級をした粉の方が常に粘弾性が大であった。