## 3 Results and Discussion
### Volatile Compounds
They could have an important role in the flavor of burgers due to their low odor thresholds. A high level of PUFA was found in the intramuscular fat of deer meats, and autoxidation could be initiated more readily in this type of meat [42]. Some authors observed aldehydes inhibition in different meat products using natural antioxidants [43; 44]. In our case, the total quantity of aldehydes increased in control samples during chilled storage in MAP; however, in the burgers with lees, it remained constant (except in the case of the Lpb sample). Certain aldehydes such as hexanal, octanal, nonanal, and (E)-2-nonenal presented less concentration in Lva burgers at the end of storage. Other compounds also originated by lipid oxidation such as hydrocarbons and ketones showed less changes because of the storage and lees addition [45]. Control samples maintained the ketones concentration over time, while the addition of lees induced a small increase in most of these compounds at day 12. No differences were observed between samples at day 0. Despite their low concentration in samples, ketones may provide pungent and rancid off-odors to meat products [41]. 1-Octen-3-one and its related alcohol, 1-octen-3-ol, with mushroom aroma, were also present in all burgers (control samples and those treated with lees). 1-Octen-3-ol, with an important role in the flavor of meat products [46], showed a significant increase during storage. Hydrocarbons are considered the main volatile compounds formed via lipid oxidation in deer cecina (Spanish smoked dry-cured meat product) [36], but they have no significant impact on flavor. Aliphatic alcohols suffered a considerable increase at the end of storage, especially in the case of 1-hexanol, which was the predominant alcohol in deer burgers after 12 days of chilled storage, followed by 1-octen-3-ol. It is remarkable that at the end of storage, many alcohols like 1-pentanol, 4-heptanol, 2-ethyl-1-hexanol, and 1-octanol showed significantly lower concentrations in burgers with wine lees than in control samples. Aliphatic acids detected in deer burgers were produced mainly by the degradation of triglycerides and phospholipids, while esters could be generated from the esterification of several alcohols and carboxylic acids in meat products during storage [46; 47]. Esters provide fruity notes, mainly those derived from short-chain acids, and slight fatty odor from long-chain acids. The addition of lees caused a high increase in the total acids and esters of burgers since these compounds are formed during wine fermentation and they are present in wine lees (Table 1). Among them, hexanoic, octanoic, and decanoic acids and their esters were the most abundant in all the samples. However, although an increase of total acids was observed in control burger after 12 days of storage, ester concentrations were significantly reduced in burgers with less, especially in the case of the ethyl decanoate. Storage led to an increase in the total of benzene compounds in the control and lees samples. Some of them, such as benzaldehyde and phenylethyl alcohol, derived from wine fermentation, increased their concentrations due to the use of lees. These compounds could improve the aroma of deer burgers with characteristic notes, while others, such as p-cymene or trimethyl benzene, with high odor thresholds, may not significantly affect the aroma of meat products [47]. Sulfur compounds can arise from the catabolism of sulfur-containing amino acids or generated by microorganisms [46; 48]. They are sensorial active compounds of meat products with pleasant notes when in moderate concentrations [41]. Only two sulfur compounds were detected in samples--carbon disulfide and 5-methyl thiazole, the last one detected after 12 days of storage at greater concentrations in samples Lvb and Lpb. Furthermore, some furanic compounds were identified, 2-pentyl furan being the most abundant, although small variations were observed with respect to control samples during storage.