Abstract

Individual milk samples from 80 cows in mid-lactation of the Swedish Red and Swedish Holstein breeds with known protein genotypes of beta- and kappa-casein and beta-lactoglobulin were analysed for acid Coagulation properties. Glucono-delta-lactone (1.5%) was added to defatted, heated (90-95 degrees C) samples and theological properties of the gels were measured using a Bohlin VOR Rheometer. Coagulation time (CT) and curd firmness after 4, 8 and 10 h (G'(4), G'(8), and G'(10) were registered for each sample. Milk protein composition was analysed by reversed phase HPLC. Concentration of beta-lactoglobulin in milk was found to be an important factor for the variation in CT and G'. The A allele of beta-lactoglobulin was associated with higher concentrations of beta-lactoglobulin in milk compared with B. When no adjustment for beta-lactoglobulin concentration was made, there was a significant overall effect of beta-lactoglobulin genotype on acid coagulation, where the AA and AB genotypes were associated with better curd firmness compared with BB, whereas at equal beta-lactoglobulin concentrations a tendency in the opposite direction was found with a significant and positive effect of BB compared with AB. Lactose concentration of milk had a positive effect on acid coagulation and was shown to improve G' in milk with low beta-lactoglobulin concentrations. (C) 2009 Elsevier Ltd. All rights reserved.

Published in

International Dairy Journal
2009, volume: 19, number: 6-7, pages: 399-404

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