Effect of destoned olive cake on the aromatic profile of cows’ milk and dairy products: comparison of two techniques for the headspace aroma profile analysis

The aim of this study, carried out within the NOVOROD project (PSR Campania 2007-2013 Misura 124 HC), was to evaluate the aromatic profile of milk and dairy products of dairy cows supplemented with destoned olive cake (DOC). Two techniques for the headspace aroma profile analysis: the thermal desorption by gas chromatography with a mass selective (GC/MS) detector and the electronic nose were compared. The trial was performed into a dairy cow farm. Ten dairy cows were allotted into two homogenous groups: control and experimental. Animals received the same diet, while in the experimental group the concentrate supplementation (15% dry matter) was replaced with DOC. After two weeks of adaptation, animals were fed with the experimental diet for other 15 days. During the experimental period, the milk was collected and cumulatively processed in Caciotta cheese (a soft cheese, 25 days ripened) and in Semicotto cheese (hard cheese, 3 months ripened) for 13 times for each group. Milk and cheese volatile organic compounds (VOCs) were extracted and concentrated with dynamic headspace method and determined by GC/MS. Statistical analysis of data, expressed in arbitrary units (a.u.=peak area × 10^–6) and allotted in compound classes, was carried out by ANOVA. All data collected of VOCs were processed with principal component analysis (PCA). Milk and cheese samples were comparatively analysed with the electronic nose, fitted with a tenmetal oxide sensors electronic device. PCA has been used for the evaluation of the pattern data. Our results show that the use of DOC, as an unconventional feed for livestock, has no effect on the aromatic profile of both milk and dairy products. In fact, no significant differences were found in both milk and dairy products between the two groups using the GC/MS method. Also the discriminating analysis carried out by electronic nose did not show significant differences between the two groups. The two compared techniques seem to lead to the same result.