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Measurement of proteolysis in milk and cheese using trinitrobenzene sulphonic acid and a new dissolving reagent

Published online by Cambridge University Press:  01 June 2009

Gérard Humbert ,
Marie-France Guingamp ,
Rosalie Kouomegne  and
Guy Linden
Gérard Humbert
Affiliation:
Laboratory of Applied Biochemistry University of Nancy 1, BP 239, 54506- Vandoeuvre-Les-Nancy, France
Marie-France Guingamp
Affiliation:
Laboratory of Applied Biochemistry University of Nancy 1, BP 239, 54506- Vandoeuvre-Les-Nancy, France
Rosalie Kouomegne
Affiliation:
Laboratory of Applied Biochemistry University of Nancy 1, BP 239, 54506- Vandoeuvre-Les-Nancy, France
Guy Linden
Affiliation:
Laboratory of Applied Biochemistry University of Nancy 1, BP 239, 54506- Vandoeuvre-Les-Nancy, France
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Extract

Milk contains indigenous plasmin-like and thrombin-like proteinases and also exogenous proteinases, mainly extracellular enzymes of psychrotrophic bacteria. Their activities lead to protein hydrolysis which may have important effects on milk quality and cheese yield. It is also useful to estimate proteolysis and its development during cheese ripening.

Milk opacity or turbidity due to calcium phosphocaseinate micelles and fat globules necessitates preliminary sample treatment, i.e. precipitation and filtration before spectrophotometric measurement. It is possible to eliminate these firs steps of sample treatment by dispersing the colloidal constituents. Some authors have already used different dissolving mixtures for sample analysis. Nakai & Anh Chi Le (1970) were the first to determine protein contents of milk and dairy products by absorbance measurement at 280 nm after clarification. Bosset & Blanc (1977) used the Biuret method. Owen & Andrews (1984) measured free amino groups with 2,4,6-trinitrobenzene sulphonic acid (TNBS). Humbert et al. (1982) and Stead (1987) used synthetic or specific substrates for proteinase determination.

In this work, we report the application of a new dissolving reagent to measure free amino groups in milk and cheese.

Type
Short Communication
Information
Journal of Dairy Research , Volume 57 , Issue 1 , February 1990 , pp. 143 - 148
Copyright
Copyright © Proprietors of Journal of Dairy Research 1990

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References

REFERENCES

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