Effect of cow feeding supplementation with olive pomace on the development of aromatic compounds in milk and dairy products

Utilization of agro-industrial by-product in animal feeding represents an interesting and sustainable alternative to its disposal. The aim of this study was to evaluate the effect of olive pomace (OP) as supplement feed in dairy cow on aromatic compounds in raw milk, spontaneous fermented milk and cheese. Twenty lactating cows were randomly divided in two homogenous groups and fed for 60 days with OP supplement (2 Kg DM/cow/die) in the experimental group (EG) and without in the control one (CG). Diets were isoenergetic and isoproteic. Samples of bulk milk were collected at the end of the trial for both groups. Some of these were spontaneously fermented at 25 C for 72h and thereafter analyzed. The rest of bulk milk was used to produce cheese that was sampled at 1, 7 and 30 days of ripening. A SPME-GC-MS analysis was performed to detect volatile compounds. Data were analyzed with GLM procedure and significance were set at p<.05. In raw milk, besides free fatty acids, several secondary lipolysis catabolites (ethyl and methyl esters, lactones, aldehydes, methyl ketones) were detected and most of them (65%) were higher in EG (p<.01). Higher lypolitic activity (48% of compounds) in fermented milk was recorded in EG confirming that already observed in raw milk (p<.05). Esters deriving from methionine catabolism were higher in EG fermented milk (p<.05). On the other hand, data generally showed an increase of first catabolites of branched amino acids in CG milk, while 45% of their related esters were most detected in the EG (p<.05). Analysis of cheese highlighted differences (p<.05) between groups in some flavoring catabolites achieved at different times during ripening. Lypolitic catabolites were generally higher in the EG, especially at T7, with the exception for d-nonalactone that was most observed in CG at every time (p<.05). First leucine catabolites (a-ketoisocaproic acid, a-hydroxyisocaproic derivative) were greater in EG cheese at every time (p<.05), while 3-methylbutanol were higher in EG at T7 (p<.001) and T30 (p<.05). Their related esters, isoamyl isopentanoate and isoamyl butyrate, increased in EG at T7 and T30 (p<.01) and at T30 (p<.05), respectively. In conclusion, dietary supplement with olive pomace may affect lypolisis and proteolysis processes responsible of dairy products aroma. This pattern was already observed in raw milk and confirmed also in fermented milk and cheese, especially for compounds produced by esterase activity.