Proteolytic volatile compounds in milk and cheese of cows fed dried olive pomace supplementation

The aim of the study was to evaluate the effect of dietary inclusion of dried olive pomace (DOP) on proteolytic volatile compounds in raw milk and pasteurised milk cheese. Two groups of lactating cows (20 animals in each) were randomly assigned to isoenergetic and isoproteic treatments provided as control mixed ration (CON) and as CON with addition of 2 kg of DOP/day/animal (EXP). DOP partially replaced maize silage, alfalfa hay, sunflower and wheat. After 60 days of feeding, raw bulk milk was collected, sampled, pasteurised and used to produce cheese that was sampled at days 1, 7 and 30 of maturation. Samples were analysed by solid phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) and data were expressed considering the relative peak area. In raw milk the phenyl-acetaldehyde and 2-phenylethyl alcohol, the only detected phenylalanine catabolites, were increased by dietary treatment by 61.9 and 235%, respectively (P < 0.01). In CON and EXP cheeses the compounds derived from phenylalanine, leucine and methionine catabolism were present being generally higher in EXP cheese during ripening time. In particular, among the volatile compounds, the contents of which were higher, were: the phenylacetaldehyde – 32.6% and 34% higher at days 7 and 30 (P < 0.01 and P < 0.05, respectively); the 2-phenylethyl alcohol – 229% higher at day 7 (P < 0.001), the 3-methyl-1-butanol – 299% and 59.1% higher at days 7 and 30 (P < 0.001 and P < 0.05, respectively), the isoamyl butyrate – 58.2% higher at day 30 (P < 0.05) and the isoamyl isopentanoate – 290% and 60.1% higher at days 7 and 30 (P < 0.01 and P < 0.05, respectively). Dietary DOP addition may affect aroma of dairy products, however the sensory evaluation panel test is needed to complete the feedback supporting industry choices.