Proteolysis detection in milk. IV. Starch-gel electrophoresis and formol titration.

Starch-gel electrophoresis (SGE) and formol titration methods for detecting proteolysis in cold-stored raw milk have been studied to establish their value as quality indices. When examined by SGE, the first evidence of proteolysis in raw milks stored at 5 degrees C was the formation of para-k-casein. However, this fraction could not be detected on the starch gels until the total bacterial count (TBC) exceeded 10-minus 7/ml. The SGE method appeared more reliable than the previously discussed tyrosine value method. Formol titration did not appear to have any application in the screening of cold-stored raw milks with TBC less than 10-minus 7/ml, but would detect some milks of poorer bacteriological quality.