Structural modifications during the primary clotting phase of milk: Luminometric methods and formation of new hydrolysis products

The primary clotting phase was monitored by using three different technique s: tristimulus colorimetry, fluorescence spectroscopy, and capillary zone e lectrophoresis (CZE). This approach could give more information on the inte rrelation between structural modifications of milk proteins and the biochem ical fenomena involved in the primary clotting phase. Different coagulation tests were carried out in different days using reconstituted skim milk pow der as standard substrate and the same liquid calf rennet solution. The clo tting time was calculated by both using a Formagraph instrument and visual observation of floks formation. Luminometric data showed two critical event s during primary clotting phase. The first one recorded the beginning of th e micellar aggregation. The second one, in accordance also with the Flocks Formation, detected the clotting point, two-four minutes before Formagraph in correspondence of the total micellar aggregation. Electropherograms obta ined by CZE procedure permitted To follow the Caseino-Macro-Peptide (CMP) f ormation.