Lipoproteic matrix

Three different milk samples were analysed by P solid-state NMR spectroscopy a milk powder sample ( PL60 obtained from a tangential microfiltration of skim milk, Triballat, France) rehydrated at 68% (32% PL60 w/w in D2O, pH=6.37), a lipoproteic matrix as a model cheese sample and a semi-hard cheese. 

The lipoproteic matrix was prepared by mixing water (63% w/w), milk powder (29.6%) and anhydrous fatty matter (7.4%) in a blender. The pH was adjusted to 6.20 by an addition of 8-glucono-lactone. Once that pH reached, the coagulation was activated by an addition of rennet. After 3h at 32°C, the preparation was kept at 4°C before NMR analysis. The water/milk powder ratio in the lipoproteic matrix equals 68/32. 

Table 1 Estimated composition of milk powder, lipoproteic matrix and semi-hard cheese...

CPMAS and SPEMAS P NMR spectra of the lipoproteic matrix are shown in Figure 4. The P CPMAS spectrum appears as a broad central signal with spinning sidebands from each side (inset of figure 4A). These sidebands, which are also observed on the SPEMAS spectrum (not shown) arise fix)m the broad resonance of the CP signal and indicate that CSA was not averaged to zero in these conditions. 

Based on the miUc powder and lipoproteic matrix spectrum analyses, we identified and estimated the proportion of mobile and immobile phosphorylated molecules in the semi-hard cheese (Table 2). 

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