Dynamic ultra-high pressure homogenisation of milk casein concentrates: Influence of casein content

• Ultra-high pressure homogenisation (UHPH) of casein concentrate at pH 5.8 can be used as ingredients for dairy based products to provide structure to milk, cheese and other acidified products.
• The mobility of water was decreased in samples with low whey protein content compared to samples with high whey protein content.
• Overall the 31P NMR spectra revealed no effect of UHPH, which indicate that UHPH does not induce measureable structural changes in the structure of the in-dividual molecules.

Milk casein concentrates with different casein-to-protein ratios (0.82 and 0.93), pH (5.8, 6.2 and 6.7) and level of applied ultra-high pressure homogenisation (UHPH) (0, 150 and 300 MPa) were studied. Samples with a casein-to-protein ratio of 0.93 at pH 5.8 and subjected to UHPH treatment at 300 MPa had the highest apparent viscosity and particle size followed by similar samples with a casein-to-protein ratio of 0.82. Water mobility was reduced at higher casein-to-protein ratio and with higher pH, while increased water mobility was observed in samples with a casein-to-protein ratio of 0.82 at pH 5.8 subjected to UHPH treatment at 300 MPa. The 1H and 31P NMR spectra revealed minor structural effects of adding casino-phospho-peptides and changing pH, but no effect of UHPH treatment, which indicate that UHPH treatment did not induce measureable structural changes in the individual proteins but rather induced changes in the tertiary structure or degree of polymerisation.Industrial relevanceMilk depleted from whey protein is advantageous to use in cheese production since it can be further processed without detrimental denaturation of whey protein which will result in reduced maturation of cheese. In combination with pH control and ultra-high pressure homogenisation of the milk casein concentrate structural changes in the protein can be obtained and new interesting milk based products can be developed.