Individual milk samples from 121 cows in mid lactation of the Swedish Red and Swedish Holstein breeds with known protein genotypes of b-and k-casein and b-lactoglobulin were analysed. Chromatographically pure chymosin was added to skim milk and rheological properties of the gels were measured using a Bohlin VOR Rheometer. Coagulation time (CT) and curd firmness after 25 min (G 0 25 ) were registered for each sample. The B allele of k-casein was associated with improved coagulating properties of milk, whereas the E allele showed a negative effect on these traits. The b-casein A 2 A 2 genotype was associated with inferior milk coagulation characteristics. Total protein concentration of milk was positively associated with curd firmness, but showed no association with milk coagulation time. r

Impact of milk protein composition on casein (CN) retention in curd during the milk coagulation process was studied using a model cheese making system. Individual milk samples from 110 cows in mid lactation of the Swedish Red and Swedish Holstein breeds with known genotypes of beta-casein, kappa-casein and beta-lactoglobulin were defatted, coagulated with chymosin, subjected to syneresis and subsequent pressing simulated by centrifugation. The results indicated that kappa-casein concentration of milk plays an important role in the curd formation process and initial syneresis (whey after cutting), whereas an increased CN ratio was associated with less casein in whey after simulated pressing. Increased kappa-casein concentration of milk also characterized the milk samples with no measurable loss of casein in whey, compared with milk samples with casein lost in whey, both after cutting and after simulated pressing. Concentrations of alphas1-casein, beta-casein, and total casein in milk were positively associated with fresh curd yield, which showed a strong correlation with amount of casein retained in curd. No effect of protein genotype on fresh curd yield or casein in whey was found. The beta-lactoglobulin BB genotype was associated with increased casein retention in curd, most likely due to the association of this genotype with CN ratio.

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The effect of fermentation by Lactobacilli and of proteolytic hydrolysis of whole milk on the IgE binding ability of beta-lactoglobulin was studied using an ELISA inhibition assay. Sera from nine adult milk allergic patients were tested. The individual sera showed a similar inhibition pattern in the changes during fermentation and proteolysis. The degradation of beta-lactoglobulin was studied with liquid chromatography. In general, fermentation with Lactobacilli gave little effect on IgE binding, even though chromatography data showed a gradual degradation of beta-lactoglobulin. Proteolysis with trypsin, however, gave extensive degradation of beta-lactoglobulin and strongly decreased IgE binding. In addition, we measured the inhibition pattern of beta-lactoglobulin in various selected commercially available fermented milk products. These showed an IgE binding capacity similar to that of nonfermented high pasteurized milk.