# The Effect of High-Pressure Treatment and Skimming on Caprine Milk Proteins
## 3 Results and Discussion
The pressure-induced changes in color of whole milk, increasing with a rise in pressure, were reported by [PERSON] et al. (2011) and [PERSON] et. al. (2012). \begin{table}
\begin{tabular}{c c c c c} \hline
**Milk** & **CN (\(\alpha\)- + \(\beta\)- + \(\kappa\)-CN)** & **WP (\(\beta\)-LG + \(\alpha\)-LA)** & **CN:WP** \\ \hline \multirow{6}{*}{Whole milk} & 0.1 MPa & 72.60 \(\pm\) 1.67 \({}^{\text{a}}\) & 27.40 \(\pm\) 1.67 \({}^{\text{a}}\) & 2.66 \(\pm\) 0.22 \({}^{\text{b}}\) \\  & 200 MPa & 71.70 \(\pm\) 0.55 \({}^{\text{a}}\) & 28.30 \(\pm\) 0.55 \({}^{\text{a}}\) & 2.53 \(\pm\) 0.07 \({}^{\text{b}}\) \\  & 300 MPa & 71.80 \(\pm\) 1.08 \({}^{\text{a}}\) & 28.20 \(\pm\) 1.08 \({}^{\text{a}}\) & 2.55 \(\pm\) 0.14 \({}^{\text{b}}\) \\  & 400 MPa & 71.99 \(\pm\) 0.37 \({}^{\text{a}}\) & 28.01 \(\pm\) 0.37 \({}^{\text{a}}\) & 2.57 \(\pm\) 0.05 \({}^{\text{b}}\) \\  & 500 MPa & 73.56 \(\pm\) 2.45 \({}^{\text{b}}\) & 26.44 \(\pm\) 2.45 \({}^{\text{b}}\) & 2.80 \(\pm\) 0.36 \({}^{\text{a}}\) \\ \hline \multirow{6}{*}{Skim milk} & 0.1 MPa & 70.22 \(\pm\) 1.02 \({}^{\text{a}}\) & 29.78 \(\pm\) 1.02 \({}^{\text{a}}\) & 2.36 \(\pm\) 0.12 \({}^{\text{b}}\) \\  & 200 MPa & 70.65 \(\pm\) 1.06 \({}^{\text{a}}\) & 29.35 \(\pm\) 1.06 \({}^{\text{a}}\) & 2.41 \(\pm\) 0.12 \({}^{\text{b}}\) \\ \cline{1-1}  & 300 MPa & 71.50 \(\pm\) 0.81 \({}^{\text{a}}\) & 28.50 \(\pm\) 0.81 \({}^{\text{a}}\) & 2.51 \(\pm\) 0.10 \({}^{\text{b}}\) \\ \cline{1-1}  & 400 MPa & 71.34 \(\pm\) 1.07 \({}^{\text{a}}\) & 28.66 \(\pm\) 1.07 \({}^{\text{a}}\) & 2.49 \(\pm\) 0.13 \({}^{\text{b}}\) \\ \cline{1-1}  & 500 MPa & 73.67 \(\pm\) 0.82 \({}^{\text{b}}\) & 26.33 \(\pm\) 0.82 \({}^{\text{b}}\) & 2.80 \(\pm\) 0.12 \({}^{\text{a}}\) \\ \hline \multirow{6}{*}{Significance (\(p\) value)} & P & 0.018 & 0.018 & 0.017 \\  & S & NS & NS & NS \\ \cline{1-1}  & p \(\times\) s & NS & NS & NS \\ \hline \end{tabular} Abbreviations: p, pressure; s, skimming; p \(\times\) s, pressure and skimming interaction. Mean values \(\pm\) SD; n = 4. Values with different superscripts in the CN column, WP column and the CN:WP column differ significantly at \(p<0.05\), depending on the applied pressure; NS—not significant.  
\end{table} 
Table 3: The effect of high-pressure treatment on the content of \(\alpha\)-casein (\(\alpha\)-CN), \(\beta\)-casein (\(\beta\)-CN), \(\kappa\)-casein (\(\kappa\)-CN), \(\beta\)-lactoglobulin (\(\beta\)-LG) and \(\alpha\)-lactalbumin (\(\alpha\)-LA) in whole and skim caprine milk (g/100 g of protein). The values of \(\Delta\)E were lower in skim milk HP-treated at 200 MPa than in the corresponding sample of whole milk. The highest values of \(\Delta\)E were noted in skim milk obtained from milk HP-treated at \(\geq\)300 MPa (Figure 3). \(\Delta\)E values were higher in skim milk than in whole milk HP-treated at \(\geq\)300 MPa, which indicates that differences in color resulted mainly from changes in colloidal phase components. Changes in the color of milk can be attributed to the modification of colloidal and emulsion phase components, namely changes in the size of casein micelles that undergo disaggregation and aggregation [33], as well as changes in the number and size of milk fat globules and their aggregates [34]. The increase in the total color difference of HP-treated skim milk was indicative of changes in the colloidal milk phase, in particular under exposure to \(\geq\)300 MPa. The main caprie milk proteins are casein and its fractions: \(\alpha\)s1-casein \(\alpha\)s2-casein, \(\beta\)-casein and \(\kappa\)-casein, which, together with colloidal calcium phosphates, are the structural components of casein micelles. Literature data partly explain the influence of HP-treatment at \(\geq\)300 MPa on the total color difference in skim caprie milk. According to research, the decrease in the lightness of HP-treated milk resulted mainly from changes in the size of protein molecules and casein disaggregation into submicelles at \(<\)150 MPa [4,5].