Natural Milk Lipase: Influence of its activity on the free fatty acids and volatile compound profiles of cheeses during ripening.

PEROTTI M.C.; VÉLEZ, M. A.; WOLF, I.; CANDIOTI, M.; HYNES, E.; ZALAZAR C.A.

Praga (República Checa).

Simposio; 4th International Sympoium on Recent Advances in Food Analysis. Asistencia, presentación de resumen y poster.; 2009

Institute of Chemical Technology, Czech Republic. International Association of Environmental Analytical Chemistry. Institute of Food Safety and Wageningen University

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB; mso-fareast-language:ES-TRAD;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Moderated lipolysis is a desirable event during ripening of hard cooked cheeses, as it increases piquant taste and genuine flavour. Milk possesses an indigenous lipolytic enzyme, the lipoprotein lipase, which is associated to casein micelle. However, its activity on triglycerides is limited because milk fat is protected by the milk fat globule membrane (MFGM).This work was aimed at increasing fat hydrolysis and flavour compounds production in hard cheeses by increasing LPL activity and improving its access to milk triglycerides. For this purpose, hard cheeses (Reggianito type) were produced in pilot plant and ripened during 90 days. The effect of influence of two different factors was studied: the method of milk sanitization and the accessibility enzyme-triglycerides. These factors were studied by comparing milk with native and damaged MFGM, and pasteurized milk and non thermally-sanitized milk.The free fatty acids (FFA) were investigated by gas chromatography (GC-FID) as ethyl esters and quantified with the internal standard method at the beginning and the end of the ripening. The volatiles compounds were isolated by microextraction in solid phase (SPME) and analysed by GC-FID/MS. The areas were quantified in arbitrary units.For all cheeses, it was observed that the degree of lipolysis increased during ripening being similar for all the treatments. However, the profiles of FFA showed differences in the relative proportions of the FFA groups. In particular, the percentage of short chain fatty acids (SCFA) was higher in the cheeses made with no-thermally treated milk than in those made with pasteurized milk. This fact suggests that the LPL played a role in lipolysis, as it has a positional specificity to the sn-3 position of the triglyceride, where SCFA are esterified. Similar results were obtained for most of the volatile compounds that constitute the groups of ketones, alcohols, esters (derivated of FFA catabolism) and the group of acids (derivated of lipolysis). Overall, the greatest area values were obtained for the cheeses made with no pasteurized milk.In cheeses made with not heated milk and with native fat, the percentage of SCFA and the levels of the volatile compounds were in general higher than those found in cheeses made with milk in which the MFGM was damaged. However, the opposite behavior was found in cheeses made with pasteurized milk. In the conditions of the study, results suggest that thermal treatment had a higher impact on cheese lipolysis and volatile compounds production than the destabilization of the fat emulsion.