Alternative Sicilian cheeses: identification of markers by a chemometric approach

Chemometric techniques play a key role in ensuring foods authenticity, as well as milk and dairy products1. Several factors, such as religious concerns (Islam, Judaism), diet (vegetarianism), or the ban on the use of genetically modified rennet, have encouraged research into alternative milk coagulants1. Among plant-derived enzymes, actinidin is a protease from kiwi, which has shown great potential for use as a milk coagulant in cheese production. In this study, samples of fresh cheeses produced with vegetable coagulants of kiwi extract2, traditional calf rennet and microbial rennet were evaluated for nutritional properties and sensory profiles in order to identify chemical markers to differentiate the three cheesemaking experiments. A data matrix was constructed using the analysis results as variables. The Kruskal-Wallis test was applied to investigate the significance of the differences between the groups of samples (cases) according to the different coagulants used. PCA, used to group samples according to analytical parameters, was complemented by a stepwise linear discriminant analysis to discriminate between different types of cheeses on the basis of the F-value. The results of the multiple comparisons showed significant differences for many of the variables analyzed, and categorization between the samples was achieved. High discriminatory power was achieved by the canonical discriminant functions, due to the high correlation values (1.000) and the low values of Wilks’ lambda (0.000). From the values of the standard coefficients, it can be stated that the variables with the best discrimination are coumaric acid, stigmasterol, C20:1 n-9, C18:2 cis9 cis12, so each case was assigned to the group to which it was most likely to belong. Overall, 100.0% of the original pooled samples were correctly classified and 100.0% of the cross-validated pooled samples were also correctly classified. The data obtained showed that the chemometric analysis can be used to correctly differentiate the alternative cheeses.