Multivariate analysis of proteolysis patterns differentiated the impact of six strains of probiotic bacteria on a semi-hard cheese

Reverse phase liquid chromatography profiles of water-soluble extract of control (C cheese) and probiotic cheeses with the direct addition of Lactobacillus casei C2 (L cheese) and by a 2-step fermentation method (P cheese) at 60 d of ripening. Letters a to q indicate the peaks selected for principal component analysis.

Principal component (PC) analysis of peptide profiles: score plot (PC1 vs. PC2) of 60-d-old cheese samples: control cheeses (+) and probiotic cheeses with Lactobacillus acidophilus A1 (▴), Lb. acidophilus A2 (○), Lb. acidophilus A3 (■), Lactobacillus paracasei C1 (●), Lactobacillus casei C2 (*), and Lactobacillus rhamnosus C3 (×). C = control cheeses without probiotics; L = cheeses with probiotic bacteria added directly as a lyophilized culture; P = cheeses with probiotic bacteria added by a 2-step fermentation method. Rectangles enclose cheese samples in a cluster by hierarchical cluster analysis.

Principal component (PC) analysis of peptide profiles: score plot (PC3 vs. PC4) of 60-d-old cheese samples: control cheeses (+) and probiotic cheeses with Lactobacillus acidophilus A1 (▴), Lb. acidophilus A2 (○), Lb. acidophilus A3 (■), Lactobacillus paracasei C1 (●), Lactobacillus casei C2 (*), and Lactobacillus rhamnosus C3 (×). C = control cheeses without probiotics; L = cheeses with probiotic bacteria added directly as a lyophilized culture; P = cheeses with probiotic bacteria added by a 2-step fermentation method. Rectangles enclose cheese samples in a cluster by hierarchical cluster analysis.

Total amount of free amino acids (mg/100g of cheese) in control and experimental (L and P) cheeses at 3 and 60 d of ripening. C = control cheeses without probiotics; L = cheeses with probiotic bacteria added directly as a lyophilized culture; P = cheeses with probiotic bacteria added by a 2-step fermentation method.

Principal component (PC) analysis of individual amount of free amino acids. (A) Score plot (PC1 vs. PC2) of 60-d-old cheese samples: control cheeses (+) and probiotic cheeses with Lactobacillus acidophilus A1 (▴), Lb. acidophilus A2 (○), Lb. acidophilus A3 (■), Lactobacillus paracasei C1 (●), Lactobacillus casei C2 (*), and Lactobacillus rhamnosus C3 (×). C = control cheeses without probiotic bacteria; L = cheeses with probiotic bacteria added directly as a lyophilized culture; P = cheeses with probiotic bacteria added by a 2-step fermentation method. Rectangles enclose cheese samples in a cluster by hierarchical cluster analysis. (B) Loading plot of amino acids (PC1 vs. PC2).