The aim of the present work was to assess the role of milk single protein fractions (αs1-CN, αs2-CN, β-CN, κ-CN, β-LG, α-LA), which are expressed as content in milk (g/l) or percentage of total casein content (Ês), on milk rennet coagulation, curd firming and syneresis. Individual milk samples were collected from 1,271 Brown Swiss cows reared in 85 herds in the Trento Province (North-East Italy). The herds were divided in 4 types according to their farming system (from traditional to modern systems). The coagulation process was assessed on each milk sample using computerized lactodynamographs and extending the test to 60 min. This analysis provided the traditional milk coagulation properties (MCP): rennet clotting time (RCT), curd firming time (k20), curd firmness at 30 (a30) and 45 min (a45). The curd firmness recorded over time every 15 sec (CFt) was processed using a four-parameters nonlinear model, which yielded new parameters of coagulation, curd firming and syneresis: RCT estimated from the equation (RCTeq), the asymptotic potential CF (CFP), the curd firming and syneresis instant rates constant (kCF and kSR), the maximum CF value (CFmax) and the time of attainment (tmax). All these traits were analysed fitting two linear mixed models according to the expression of milk protein fractions included: M-g/l and M-Ês. The other effects included were herd (random effect), daily milk production (only for M-g/l), casein content (only for M-Ês), farming system, parity, days in milk, pendula of the instruments and CSN2, CSN3, BLG genotypes. The results showed a positive role of αs1-CN and β-CN on the CFmax, with the former having an effect almost double than the latter. The κ-CN had a favourable effect on the milk coagulation ability, reducing RCT, increasing the kCF and kSR and allowing to reach a higher CFmax. In contrast, the results showed an unfavourable effect of αs2-CN on both RCTs and of β-LG on curd firming. These results could be useful for the improvement of cheese production traits in cattle breeding programs.
Role of milk protein fractions on coagulation, curd firming and syneresis
N. Amalfitano;C. Cipolat-Gotet;A. Cecchinato;G. Bittante
2018
Abstract
The aim of the present work was to assess the role of milk single protein fractions (αs1-CN, αs2-CN, β-CN, κ-CN, β-LG, α-LA), which are expressed as content in milk (g/l) or percentage of total casein content (Ês), on milk rennet coagulation, curd firming and syneresis. Individual milk samples were collected from 1,271 Brown Swiss cows reared in 85 herds in the Trento Province (North-East Italy). The herds were divided in 4 types according to their farming system (from traditional to modern systems). The coagulation process was assessed on each milk sample using computerized lactodynamographs and extending the test to 60 min. This analysis provided the traditional milk coagulation properties (MCP): rennet clotting time (RCT), curd firming time (k20), curd firmness at 30 (a30) and 45 min (a45). The curd firmness recorded over time every 15 sec (CFt) was processed using a four-parameters nonlinear model, which yielded new parameters of coagulation, curd firming and syneresis: RCT estimated from the equation (RCTeq), the asymptotic potential CF (CFP), the curd firming and syneresis instant rates constant (kCF and kSR), the maximum CF value (CFmax) and the time of attainment (tmax). All these traits were analysed fitting two linear mixed models according to the expression of milk protein fractions included: M-g/l and M-Ês. The other effects included were herd (random effect), daily milk production (only for M-g/l), casein content (only for M-Ês), farming system, parity, days in milk, pendula of the instruments and CSN2, CSN3, BLG genotypes. The results showed a positive role of αs1-CN and β-CN on the CFmax, with the former having an effect almost double than the latter. The κ-CN had a favourable effect on the milk coagulation ability, reducing RCT, increasing the kCF and kSR and allowing to reach a higher CFmax. In contrast, the results showed an unfavourable effect of αs2-CN on both RCTs and of β-LG on curd firming. These results could be useful for the improvement of cheese production traits in cattle breeding programs.
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