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A study of surface hydrophobicity of milk proteins during enzymic coagulation and curd hardening

Published online by Cambridge University Press:  01 June 2009

Claudio Peri ,
Ella Pagliarini ,
Stefania Iametti  and
Franco Bonomi
Claudio Peri
Affiliation:
Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Universitá di Milano, Italy
Ella Pagliarini
Affiliation:
Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Universitá di Milano, Italy
Stefania Iametti
Affiliation:
Dipartimento di Scienze Molecolari Agroalimentari, Università di Milano, Italy
Franco Bonomi
Affiliation:
Dipartimento di Scienze Molecolari Agroalimentari, Università di Milano, Italy
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Summary

The formation of hydrophobic sites on the surface of casein micelles as a consequence of rennet action has been followed through the binding rate of a fluorescent probe and its distribution between a free and an ‘aggregated’ protein fraction. The variation of this parameter has been related to clotting time and curd hardening kinetics.

Results show that a first aggregation of casein through hydrophobic sites interaction began as soon as rennet was added to milk. At the natural pH of milk, the sol-gel transition occurred when all the casein micelles were already involved in large aggregates. This was not the case with slightly acidified milk (pH 6·5 and 6·3) where clotting occurred well before the first aggregation step had been completed. The surface hydrophobicity of casein continued to increase in the curd due to continuing enzymic action and structural rearrangements. When this process has been completed the hardening of curd proceeds at an accelerated pace until it reached its maximum asymptotic value.

Type
Original Articles
Information
Journal of Dairy Research , Volume 57 , Issue 1 , February 1990 , pp. 101 - 108
Copyright
Copyright © Proprietors of Journal of Dairy Research 1990

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References

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