Application of Microparticle-Enhanced Nephelometric Immunoassays of Alpha-Caseins, Beta-Caseins and Kappa-Caseins to Evaluate Quality of Milk, from the Production to the Valorization in Cheese Industry

alpha-, beta- and kappa-caseins were assayed, using a microparticle-enhanced nephelometric immunoassay, in 1300 milk samples, collected fortnightly during 13 months (october 1992 to october 1993), from 50 herds from Normandie (France). The concentration of these three caseins was compared with those of other milk compounds (protein, fat, lactose and dry matter). The main factors defining milk composition and related to the farm, herd, herd management and feeding, were then studied. The biochemical composition and rennet-coagulation (rennet coagulation time, firming time K15, and firmness parameter A30) were evaluated during the same period, in raw and fat-standardized milks, used in an industrial production of cheese. Performed in short and narrow limits, our work was a global study on milk from the production to the valorization in cheese industry. It allowed to confirm well known and copiously published results concerning milk biochemistry (relations between composition parameters, evolution and variability of these parameters), zootechnology (influence of breed, pedologic potentialities of the grazing soils, seasonal distribution of calving, feeding conditions of transition from stabbling to pasture) and cheese-making (relative influence of the parameters of composition on the rennet-coagulability bf milk and cheese-making yields). Microparticle-enhanced nephelometric immunoassay, allowing a specific and accurate assessment of the milk casein, thus appeared as an immunoanalytical method, completing the traditional tools for the evaluation of milk quality.