FIGURE 4 | Loadings, scores and observed vs. predicted plots following OPLS model predictive of the pHu value. (A) Loadings of the OPLS model (M2; training dataset) with the pHu as quantitative factor Y and the lipids as explanatory quantitative variables X. The model composed of 1 predictive and 2 orthogonal components was fi tted to 40 lipids. The cumulative explanatory and predictive performance of this model (M2) were R 2 Y (cum) = 0.69 and Q 2 (cum) = 0.62. (B) Scores plots following OPLS. Circles correspond to the chicken tags colored according to their measured pHu value in the Pectoralis major muscle. (C) Observed vs. predicted after 7- fold cross validation plot. The root mean squared error of the estimation (RMSEE) and the root mean squared error after cross validation (RMSECV) were 0.18 and 0.20 pH unit, respectively.