Common components and specific weights analysis: a tool for monitoring the molecular structure of semi-hard cheese throughout ripening.

Twelve semi-hard (Raclette) cheeses, belonging to four brand products, namely A (n=3), B (n=3), C (n=3) and D (n=3), were produced during summer period and ripened at an industrial scale. Tryptophan, riboflavin and vitamin A fluorescence spectra were scanned on the 12 cheeses at 2, 30 and 60 days of ripening. The physico-chemical analyses were performed only at the end of the ripening stage (60 days). Common components and specific weights analysis (CCSWA) were applied on the four data tables. CCSWA showed that the common component 1 (q1), discriminating cheeses labelled A, B and C from those labelled D, expressed 94.4 and 59% of the inertia of vitamin A and tryptophan fluorescence spectra and a less amount for riboflavin fluorescence spectra and physico-chemical data (24.2 and 13.2%, respectively). Common component 3 (q3), differentiating between cheeses labelled B and those labelled A and C, explained 34.6 and 23.9% of the inertia of the physico-chemical data and tryptophan fluorescence spectra, respectively, and a tiny part of the inertia of riboflavin and vitamin A fluorescence spectra (3.2 and 0.7%, respectively). The CCSWA showed its ability to describe the overall information collected from fluorescence and physico-chemical data tables and to extract relevant information at the molecular level throughout ripening of the investigated semi-hard cheeses.