Comparison of Four Methods for Determining Protease Activity in Milk

Authors

  • K. K. H. KWAN,

    1. Authors Kwan, Nakai, and Skura are affiliated with the Dept. of Food Science, Univ. of British Columbia, Ste. 248 – 2357 Main Mall, Vancouver, British Columbia Canada, V6T 2A2.
    Search for more papers by this author
  • S. NAKAI,

    1. Authors Kwan, Nakai, and Skura are affiliated with the Dept. of Food Science, Univ. of British Columbia, Ste. 248 – 2357 Main Mall, Vancouver, British Columbia Canada, V6T 2A2.
    Search for more papers by this author
  • B. J. SKURA

    1. Authors Kwan, Nakai, and Skura are affiliated with the Dept. of Food Science, Univ. of British Columbia, Ste. 248 – 2357 Main Mall, Vancouver, British Columbia Canada, V6T 2A2.
    Search for more papers by this author

  • Presented at the 42nd Annual Meeting of the Institute of Food Technologits. Las Vegas, NV, June 22–25, 1982.

  • This research was supported by a grant from the British Columbia Ministry of Agriculture and Food and by a research contract from the Canadian Dairy Commission (OSU81–00259).

ABSTRACT

Four methods (absorbance at 280 nm; the Lowry method; the fluor-escamine method, and the trinitrobenzenesulfonic acid method) for determining hydrolysis of milk proteins were compared. Each method was applied to the trichloracetic acid soluble fraction of milk protein, which had been digested with trypsin for various periods of time. Detectability was measured as the ratio between standard error of estimate and slope calculated from the linear regression analysis of Deming for cases when both variables were subject to error. Although it was nondimensional, the detectability thus calculated was simple and reliable for comparing assay methods which were based on different analytical principles. Detectability as well as the detection limit measured according to Schwerdtfeger showed that, of the methods compared, the fluorescamine method was most reliable and sensitive.

Ancillary