Caseinomacropeptide monitoring by capillary zone electrophoresis (CZE) and interpretation of structural modifications during the primary clotting phase of milk

A Capillary zone electrophoresis (CZE) procedure was used to detect Caseinomacropeptide (CMP) formation during the primary clotting phase of milk. Fluorescence spectroscopy was used to give more information on the interrelation between structural modifications of milk proteins and primary clotting phase, monitored by tristimulus colorimetry. Different coagulation tests were carried out on different days using reconstituted skim milk powder, as standard substrate, and the same liquid calf rennet solution. CZE, tristimulus colorimetry and fluorescence spectroscopy were performed in parallel every day. Clotting time was calculated by using both a Formagraph instrument and visual observation. Techniques used were able to detect the same critical points associated with the sequence of structural modifications and conformational changes occurring on casein fractions. The CZE method was suitable to identify and quantify CMP during the whole coagulation phase. The fluorimetric method was able to detect conformational changes in milk proteins during the coagulation process. Tristimulus colorimetry results were confirmed. Furthermore, it was possible to confirm the relationship between CMP formation and structural modifications on the casein micelle surface.