## 3 Results and Discussion
### Volatile Profile of Fermented Milks  
Main volatile compounds in fermented millks were analyzed in samples from PE (before introducing silages in the diet) and LL (after four months in different diets), results are presented in Table 10 as prevalence of each volatile compound (% of area). Fifty-one compounds were identified in millks fermented by the mesophilic culture MA400 being 11 aldehydes, 8 hydrocarbons, 8 terpenes, 7 ketones, 6 esters, 5 alcohols, 5 acids and 1 sulfur compound. Forty-five compounds were identified in millks fermented by the thermophilic culture YO-MIXTM300: 10 aldehydes, 7 hydrocarbons, 6 terpenes (some of them in the limit below 0.2 prevalence), 7 ketones, 6 esters, 4 alcohols, 4 acids and 1 sulfur compound. The prevalence of the chemical families is similar to the previously reported in other fermented goat milk products [19]. Most of the compounds were isolated in both type of fermented millks, although with different prevalence. Major compounds in milk cultured with both cultures were hexanal, 2-heptanone, heptanal, hexanoic acid, octanal, 2-ethylhexanol, benzyl alcohol, 2-nonanone, nonanal and nonanediol. Five of the identified compounds are considered key compounds in the flavor of fermented millks: acetoin, hexanal, 2-heptanone, 2-nonanone and nonanal [53]. Regarding the compounds mainly responsible for the goaty flavor, hexanoic acid was the most prevalent and showed a tendency to increase at late lactation and also in fermented milk from broccoli BD and artichoke plant silages APD fed groups. Hexanoic acid is also recognized as a major source of flavor in fermented milks [54]. Octanoic and decenoic acids had a lower prevalence and were not affected by lactation stage. The prevalence of volatile compounds in fermented millks by mesophilic culture was modified due to lactation stage for the following compounds: hexanal, heptanal, dodecane and tridecance decreased at late lactation, whereas butanoic acid, 2-heptanone, 2-nonanone increased. Regarding the diet, it significantly modified the prevalence of several compounds. Butanoic acid, hexanoic acid, octanal and octanoic acid were more prevalent in those FMs from diets including silages (BD and ADP), whereas heptanal, benzyl alcohol, nonanal and methyl salicate contents were lower than in CD. The inclusion of broccoli significantly (\(p<0.05\)) increased 2-heptanone prevalence in fermented milk. In the case of the thermophilic culture, the lactation stage affected acetoin, hexanal, heptanal, octanal, nonanediol and decanal that decreased, whereas 2-heptanone, hexanoic acid, ethyl-hexenol, benzyl alcohol, 2-nonanone, octanoic acid and decanal increased at late lactation. The diet caused significant differences on hexanal, nonanal and decanal that increased due to the inclusion of silages (BD and APD) and 2-heptanone and octanoic acid that decreased as compared to CD at late lactation. The inclusion of broccoli silage yielded milk with reduced prevalence of heptanal and cubebene. The inclusion of artichoke plant silage caused a decreased prevalence of 2-nonanone. Overall, aldehydes decreased at late lactation in both fermented millks regardless the diet. Aldehyde content in fermented millks is mainly dependent on the enzymatic activity of the substrate as they are produced from the degradation of milkfat or from the catabolism of aminoacids, and they are degraded by oxidation to carboxylic acids or by reduction to alcohols [55]. In milk cultured with MA400 the prevalence of acids increased when silages were included in the diet, so expecting those products as having higher goaty flavor, whereas in milk fermented with yogurt culture aldehydes prevalence increased when silages were included, so expecting green and fresh flavors. When handling the samples, authors perceived them all as having mild odor and no evident odor differences were detected among groups, in the future, sensory analysis would be of interest to evaluate flavor perception in detail.