## 4 Discussion  
The latest trends in the composition of fermented meat products are directed to the reduction of additives such as nitrifying agents, which include nitrates and nitrites. Our previous studies [12; 13; 14] on selected parameters related to food safety and the bioactive compound content in fallow deer and beef fermented sausages without nitrite showed that the addition of freeze-dried acid whey powder improved the CLA content of meat products, thereby improving their nutritional value. Moreover, the use of freeze-dried acid whey allows obtaining non-nitrite fermented sausages with similar parameters related to food safety as cured sausages, including the content of bioactive amines. Of the three levels of whey added to fermented sausages used in the above-mentioned studies, the equivalent of 10% liquid acid whey, corresponding to 0.7% freeze-dried whey powder, seems to be the most advantageous. The present study using this amount of whey powder for fermented sausages showed a significant effect on the volatiles profile. The products with the material tested in this experiment were characterized by an average pH in the range of 5.23-5.37 and 5.66-5.79 for beef and fallow deer fermented sausages, respectively. Their water activity at the end of production was relatively low (0.910-0.918). The observed pH and water activity parameters indicated unfavorable conditions preventing the growth of the most abundant bacteria in meat products such as _Listeria monocytogenes_, _Clostridium botulinum_, and _Escherichia coli_. Elimination of nitrite as well as the addition of freeze-dried acid whey powder did not cause statistically significant changes in the values of TBARS in fermented sausages at the end of production. TBARS refersto the content of substances that react with thiobarbituric acid, mainly malondialdehydedehyde. Malondialdehydedehyde is one of the most abundant aldehydes generated during secondary lipid oxidation and also probably the most commonly used as an oxidation marker [31]. It is a reactive aldehyde that forms interactions with nucleic acids and covalent protein adducts, thus contributing to its toxicity [32], especially in meat and meat products. It is usually considered a biomarker of oxidative stress in an organism. Covalent modification of lipoproteins with MDA may play a pathogenic role in atherosclerosis [33]. According to the literature [34], the acceptable limit of TBARS in which there is no rancidity in meat and meat products is 2.0-2.5 mg MDA/kg. In the current study, beef fermented sausages were characterized by slightly higher values of TBARS than the indicated limits and significantly higher compared to fallow deer sausages. This may be due to the higher content of unsaturated fatty acids particularly susceptible to oxidation processes in beef fermented sausages as shown by the analysis of the fatty acid profile. Moreover, analysis of the main fractions of fatty acids indicated the effect of the elimination of nitrite on the higher content of PUFA in case of beef sausages. However, beef sausages were characterized by a significantly lower content of n-3 fatty acids, which resulted in the n-6 to n-3 ratio for these sausages being significantly higher compared to the fallow deer sausages. Although the ratio of n-6 to n-3 fatty acids for both beef and fallow deer sausages for human diets was in line with the recommendations [35], for fallow deer sausages it was more than two times lower and amounted to 1.8:1, which corresponds to the ideal ratio of around 2:1 recommended by a panel of lipid experts. The results obtained displayed a similar relationship of the values of TBARS in comparison to those obtained by [PERSON] and [PERSON] [36]. In their study, fallow deer sausages were characterized by a lower content of 2-thiobarbituric acid reactive substances than sausages made from beef meat. The higher values of TBARS are in accordance with the abundance of volatile compounds derived from lipid oxidation as they were significantly higher in beef fermented sausages. As [PERSON] et al.