Determination of caprine serum albumin in milk using bromocresol green dye.

摘要

The objective of this study was to develop and validate a rapid and sensitive analytical technique to measure caprine serum albumin (CSA) concentrations in milk, demonstrate its utility and investigate the relationship between CSA and milk constituents. The principle of the technique is based on the binding of albumin to bromocresol green (BCG) dye at pH 4.0 and the absorption of the dye-albumin complex was determined spectrophotometrically at 640nm. A linear relationship existed between CSA concentrations (0.01 to 8.0 mg/ml) and absorbance values. Intra-assay and inter-assay coefficients of variation (CV) for the proposed BCG dye-binding assay were 2.6% and 12% respectively. Recovery from milk samples spiked with albumins was 89.15% +/- 7.6. Individual milk samples (n=126) were collected from lactating Saanen goats at various stages of lactation in a local dairy herd in Quebec and the CSA concentrations in milk were assayed using the proposed BCG method. Caprine serum albumin concentrations in milk ranged between 0.31 and 0.52 mg/ml. The concentrations of CSA were significantly higher (P 0.05) at the beginning of lactation, declined rapidly and remained relatively stable in mature milk. Caprine serum albumin correlated positively (P 0.05) with somatic cell counts (SCC), total solids (TS), protein, fat and whey and correlated negatively (P 0.05) with lactose concentration and casein. The proposed BCG-dye binding method is easy to perform, rapid, sensitive, reliable and can be used to determine CSA concentrations in milk collected from goats under different physiological conditions.