Analysis On Structure Of White Visible Granule And Its Forming Cause In Bovine Milk

In the present study, we have mainly worked on the cow milk collected from two areas of Huhhot city, Inner Mongolia, and especially on an abnormal composition—―white visible granule (or called small white granule) in bovine milk. Forming cause, basic structure, and composition of small white granule were inquiried into. The result revealed that white visible granule could be dissolved in acidic and alkalic solution, ruleless granule, its diameter was smaller than 1 mm, could easily adhere on the container wall, difficult to be collected and identified visually; it mainly occurred in the milk of subclinical mastitis cows(about 99%). By combinating of all three methods of the electric conductivity detection, somatic cell counts(SCC), and the CMT method, which it was confirmed that the abnormal milk were more often happened in cows infected with subclinical mastitis. Correlativities between the small white granule number and the increment of the electric conductivity(r =0.7570), SCC(r=0.8944)showed significantly(α=0.01); Variations of level and morphological states of inorganic salts in milk have great influence on the stability of milk. Contents of potassium, sodium, calcium, magnesium of milk between normal and abnormal groups have different levels when messured by atomic absorption spectrophotometer. In abnormal group, the contents of K(33.16 mmol/L)decreased, Na(28.78 mmol/L)increased, Cl(51.72 mmol/L)increased, while Ca(29.49 mmol/L)decreased slightly. Variation of the Ca2+ concentration was very noticeable between whey phase and colloid phase of abnormal milk; The ionic strength were 0.092mol/L in abnormal group and 0.082mol/L in normal group, and had strong influence on bovine milk stability. It has positive correlativity with degree of white visible granule(r=0.5096,α=0.050). By ultracentrifuging the milk samples, the precipitation was got and then seperated by sephadex-G25 chromatography to analyge the protein components. Molecular weights of the fractions of the mixture were about 69kD, 36kD, 19kD, 23kD, 14.47kD by electrophoresis. Based on the research, the structure of the white visiable granule could be composed of calcium phosphate precipitate, milk protein ( including α-casein, κ-casein, serum albumin, β-lactoglobulin, α-lact albumin), somatic cells, and a little amount of other components.