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Casein compositional studies. III. Changes in Irish milk for manufacturing and role of milk proteinase

Published online by Cambridge University Press:  01 June 2009

William J. Donnelly  and
J. Gerard Barry
William J. Donnelly
Affiliation:
The Agricultural Institute, Moorepark Research Centre, Fermoy, Co. Cork, Irish Republic
J. Gerard Barry
Affiliation:
The Agricultural Institute, Moorepark Research Centre, Fermoy, Co. Cork, Irish Republic
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Summary

The composition of casein in Irish milk for manufacturing was examined throughout the year. Large changes in composition were observed in the final quarter of the year as a result of the influence of late lactation when the proportion of αs- and β-caseins declined and the proportion of κ- and γ-caseins and of minor casein components increased. Similar changes in casein composition were induced by treatment of milk with porcine plasmin. The activity of plasmin-like milk proteinase in milk was quantified from the rate of conversion of added [14C]β-casein to [14C]γ-caseins. This activity was considerably higher in a late lactation milk than in a mid lactation milk and was ∼ 20 times higher at 37 °C than at 4 °C. It was concluded that casein compositional changes in late lactation were largely the result of proteolysis of individual caseins by plasmin-like milk proteinase.

Type
Original Articles
Information
Journal of Dairy Research , Volume 50 , Issue 4 , November 1983 , pp. 433 - 441
Copyright
Copyright © Proprietors of Journal of Dairy Research 1983

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References

REFERENCES

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