Multiblock Analysis Applied to TD-NMR of Butters and Related Products

This work presents a novel and rapid approach to predict fat content in butter products based on nuclear magnetic resonance longitudinal (T₁) relaxation measurements and multi-block chemometric methods. The potential of using simultaneously liquid (T_1L) and solid phase (T_1S) signals of fifty samples of margarine, butter and concentrated fat by Sequential and Orthogonalized Partial Least Squares (SO-PLS) and Sequential and Orthogonalized Selective Covariance Selection (SO-CovSel) methods was investigated. The two signals (T_1L and T_1S) were also used separately with PLS and CovSel regressions. The models were compared in term of prediction errors (RMSEP) and repeatability error (<inline-formula><math display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>r</mi><mi>e</mi><mi>p</mi></mrow></msub></mrow></semantics></math></inline-formula>). The results obtained from liquid phase (RMSEP <inline-formula><math display="inline"><semantics><mo>≈</mo></semantics></math></inline-formula> 1.33% and <inline-formula><math display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>r</mi><mi>e</mi><mi>p</mi></mrow></msub></mrow></semantics></math></inline-formula><inline-formula><math display="inline"><semantics><mo>≈</mo></semantics></math></inline-formula> 0.73%) are better than those obtained with solid phase (RMSEP <inline-formula><math display="inline"><semantics><mo>≈</mo></semantics></math></inline-formula> 5.27% and <inline-formula><math display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>r</mi><mi>e</mi><mi>p</mi></mrow></msub></mrow></semantics></math></inline-formula><inline-formula><math display="inline"><semantics><mo>≈</mo></semantics></math></inline-formula> 0.69%). Multiblock methodologies present better performance (RMSEP <inline-formula><math display="inline"><semantics><mo>≈</mo></semantics></math></inline-formula> 1.00% and <inline-formula><math display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>r</mi><mi>e</mi><mi>p</mi></mrow></msub></mrow></semantics></math></inline-formula><inline-formula><math display="inline"><semantics><mo>≈</mo></semantics></math></inline-formula> 0.47%) and illustrate their power in the quantitative analysis of butter products. Moreover, SO-Covsel results allow for proposing a measurement protocol based on a limited number of NMR acquisitions, which opens a new way to quantify fat content in butter products with reduced analysis times.