Novel assay for the determination of residual coagulant activity in cheese

Citation
Mj. Hurley et al., Novel assay for the determination of residual coagulant activity in cheese, INT DAIRY J, 9(8), 1999, pp. 553-558
Citations number
21
Categorie Soggetti
Food Science/Nutrition
Journal title
INTERNATIONAL DAIRY JOURNAL
ISSN journal
09586946 → ACNP
Volume
9
Issue
8
Year of publication
1999
Pages
553 - 558
Database
ISI
SICI code
0958-6946(1999)9:8<553:NAFTDO>2.0.ZU;2-M
Abstract
A new method for determining residual coagulant activity in cheese was deve loped. Cheese samples were dispersed in 0.1 M trisodium citrate, under whic h conditions chymosin was stable for at least 5 h. On incubation of such di spersions with a synthetic heptapeptide substrate (Pro-Thr-Glu-Phe-[NO2-Phe ]-Arg-Leu) at 37 degrees C and pH 3.2, a single peptide ([NO2-Phe]-Arg-Leu) was produced from the substrate by the action of coagulant in the cheese a nd quantified by reverse-phase HPLC with detection at 300 nm. This peptide was produced at a constant rate. The concentration of this peptide was prop ortional to the amount of active enzyme present and the assay was capable o f measuring chymosin activities in buffer as low as 3.66 x 10(-4) rennet un its (RU) ml(-1). The assay was highly repeatable with a coefficient of vari ation of 4.3%, and was applied to a number of commercial cheeses for which residual coagulant activities in the range 11.1-20.1 RU kg(-1) were determi ned. The assay developed in this study is a simple, rapid, sensitive and re producible method for determining residual coagulant activity in cheese and other dairy products. (C) 1999 Published by Elsevier Science Ltd. All righ ts reserved.