カゼイン・ミセルの膠状性に関する研究

Studies of colloidal aspect on casein micelle

Yoshida Shigeru

広島大学水畜産学部紀要

Journal of the Faculty of Fisheries and Animal Husbandry, Hiroshima University

Casein micelle is the state of the dispersion in milk whey as suspension of colloidal particle containing 35.8mg calcium and 24.0mg phosphorus per gram of casein protein. This casein micelle's suspension shows the strong turbidity on account of existing the colloidal particle which scatter visible light.

When calcium ion was added, casein micelle was aggregated each other, and destabilizated in a centrifugial field, and decreased in its viscosity.

The intensity of this turbidity was measured by its optical density at 610mμ wave length by spectrophotometer. This turbidity showed a constant optical density at under 37°C. But when Ca + + was added to this casein micelle suspension, its turbidity increased suddenly and influenced remarkably with the temperature of this suspension. At the time of measurment of its turbidity, casein concentration, Ca ++ concentration, pH, ionic stength, and temperature must be corrected.

The protein portion of this casein micelle was prepared by addition of potassium oxalate, separation of calcium oxalate, and dialysis against deionic water. These procedures mean the destruction of casein micelle structure. This protein was fractionated to 4 parts by difference of solubility at 30mM calcium chloride without pH change or urea treatment. The estimation of the 4 casein fractions was provided with Tiselius Electrophoresis and D.E.A.E. cellulose column chromatography.

F-1 casein fraction, 36.3%, precipitated by 1000rpm, 200g, 10min., centrifugation with 30mM CaCl2 at 2°C, main component was αs-casein.
F-2 casein fraction, 3.8%, precipitated by 10000rpm, 7000g, 10min., centrifugation at 2°C, after F-1 casein was precipitatated, main component was seemed probably to be αs-casein.
F-3 casein fraction, 33.3%, precipitated by 20000rpm, 9000g, 20min., centrifugation at 37°C after F-1 casein and F-2 casein were removed, main components were β-casein and κ-casein.
F-4 casein fraction, 22.9% remained in supernatant after calcium sensitive casein fractions were precipitated, main component was κ-casein.

αs-casein, κ-casein and Ca++ make a complex which is Ca-αs-κ-caseinate. This complex shows a stable state at colloidal aspect, because κ-casein prevent the precipitation of Ca-αs-caseinate. β-casein, κ-casein and Ca++ make a complex of Ca-,β-κ-caseinate. This complex polimerized to Ca-β-κ-caseinate polymer at more than 20°C.

Rennin clotting is occured only when K-casein is treated with rennin.

Animal husbandry [ 640 ]

jpn

広島大学水畜産学部

[ISSN] 0440-8756

[NCID] AN00213563