A comparison of lipids in blue and white mould-ripened cheeses.

The free saturated medium chain fatty acids (FMCFA's) were isolated and analysed by gas chromatography from two blue veined cheeses (Bleu d'Auvergne and Fourme d'Ambert) and two soft-ripened cheeses (Brie and Vacherin Mont d'Or) at the point of purchase. Identification of the fatty acids was carried out using a gas chromatograph coupled to a mass spectrometer (GC/MS). The cheeses were sampled in the region of conidia spores (blue veins in the blue cheeses and surface in the soft-ripened cheeses) and the region of no obvious spores (white region in the blue cheeses and centre in the soft-ripened cheeses).In the blue veined cheeses, higher concentrations of (FMCFA's) were detected in the region of conidia spores, particularly tetradecanoic and dodecanoic acids. The concentrations of the FMCFA's in the white region of the blue cheese were similar to those in the Brie cheese. There was little difference in the concentration of the free medium chain fatty acids between the centre and surface of Brie and Vacherin Mont d'Or. Only hexanoic, octanoic and decanoic acids were detected in the Brie cheese, with octanoic acid present in the highest concentration (~ 0.4 - 0.7 mg / g cheese). In Vacherin Mont d'Or cheese, all fatty acids were detected (C6:0 - C14:0), with tetradecanoic and octanoic acids present in the highest concentrations. These results suggest that fungal metabolism is different in different regions of the cheese. The conidia in the blue cheese appear to be more metabolically active than those on the surface of the surface-ripened cheeses.A blue veined cheese (Bleu d'Auvergne) and a surface ripened cheese (Brie) were stored under simulated ripening conditions at 12°C. The free fatty acids C6:0 - C14:0 were extracted directly from the cheeses and identified by GC/MS. The lipid fraction of the cheese that contained both free and acylated medium (MCFA's) and long chain fatty acids (LCFA's), was extracted and then esterified. Identification of saturated, mono-unsaturated and methyl branched fatty acids in this fraction was carried out by GC/MS.The concentration of the FMCFA's in the blue region of the Bleu d'Auvergne cheese increased during storage, particularly the longer chain tetradecanoic and dodecanoic acids. In the Brie cheese and the white region of the blue cheese, the free fatty acid concentration remained constant during storage.Differences were evident in the lipid extract containing both free and acylated fatty acids of both the Bleu d'Auvergne and Brie cheeses. In the blue region of the Bleu d'Auvergne cheese, the MCFA concentration decreased probably due to fungal metabolism of the fat, whilst the concentration of the LCFA's increased during storage. In the white region of the cheese, both the medium and long chain fatty acid concentrations increased during storage probably due to water loss from the Bleu d'Auvergne cheese. At the surface and centre of the Brie cheese, no change in the MCFA concentration of the acylglycerol fraction was seen during storage. The LCFA's decreased in concentration in both regions, again, probably due to fungal metabolism of the fat.The pH ranged from 6.1 - 7.2 in the blue cheese and from 5.7 - 7.8 in the Brie cheese. The fat content in the blue region of the blue cheese decreased during storage, but increased in the white region, probably due to water loss from the cheese. In the Brie cheese, the fat content was higher at the surface than the centre, and decreased with time in both regions.