The extent of proteolysis was estimated by the fluorescamine assay using a combination of the methods described byKocak and Zadow (1985) and Chism et al. (1979). To 500 mL of 1.67 M trichloroacetic acid, an equal volume of UHT milk sample was added and held for 20 min. The resulting mixture was filtered through a no. 41 filter paper (Whatman PLC, Brentford, U.K.). A 12.5-mL aliquot of the filtrate was mixed with 1 mL of 100 mM sodium phosphate at pH 8.0 and 500 mL of 719 mM fluorescamine in acetone. Fluorescence of the samples was measured at an excitation wavelength of 390 nmand an emissionwavelength of 475 nmusing amodel F-2000 fluorescence spectrophotometer (Hitachi High- Technologies Corporation, Tokyo, Japan).