Fresh cow’s milk was obtained from the herd some modifications as follows: one ml of the substrate
of the dairy cattle at Faculty of Agriculture, Cairo (1% casein in 0.05 M phosphate buffer, pH 7.0) was
University, Giza, Egypt. Skim milk powder made in incubated at 37°C for 15 min and then 1.0 g of different
Poland was obtained from the local market. Fruits yoghurt samples (source of the proteolytic enzymes) was
(Papaya, pineapple, kiwi and kaki) and commercial grade added. After mixing, the prepared mixture was incubated
granulated cane sugar (Sugar and Integrated Industries at 37°C for 20 min. The reaction was terminated by adding
Co. at Hawamdia, Egypt) were also obtained from the local 2.0 ml of 0.4 M trichloroacetic acid (TCA) then filtrated
market of Cairo.