## 1 Introduction  
Fermented meat products are a traditional and high-quality food that is an important part of the European cultural heritage [1]. They are traditionally manufactured using nitrate and nitrite [2]. However, in recent years, their unique nutritional properties have been emphasized by eliminating or reducing synthetic additives in the direction of the \"clean label\" trend. Such products are considered to be healthy and much more preferred by modern consumer [3]. Nitrates and nitrites are controversial additives in meat processing due to their involvement in the formation of nitroso-compounds, such as carcinogenic N-nitroosamines [4]. To obtain clean label products, natural raw materials of plant or animal origin are used [5; 6; 7; 8] whose aim is to impart similar properties to meat products compared to products with synthetic additives. However, the elimination of nitrates/nitrites carries the risk of reducing the shelf life of meat products as these compounds are added as preservatives due to their antimicrobial activity and antioxidants properties. The beneficial effect of nitrites/nitrates in meat products is also related to the positive effect of color enhancement and the development of the flavor typical of cured meat products [9; 10; 11]. Our previous studies showed the possibility of using freeze-dried acid whey as a nitrite substitute in fermented sausages [12; 13; 14]. The addition of acid whey in uncured dry fermented sausage improved its properties including the nutritional value by improving the CLA. It was indicated that the acid whey had a similar effect on the tested parameters as nitrate/nitrite in fermented sausages. The efforts of scientists and meat processors to reduce nitrites are particularly important in the case of red meat, which includes ruminant meat (e.g., beef and fallow deer). It is well known that a high consumption of red and processed meat (e.g., cured) may exert some toxic effects on humans, such as cancer risk, the risk of heart diseases, and different metabolic disorders (diabetes, weight gain) [15; 16]. During the production of fermented meat products, as a result of the ripening process, complex chemical and biochemical changes in the main components of meat including proteins and lipids lead to the generation of flavor precursors such as peptides, free amino acids, and free fatty acids, which are transformed to volatile compounds [17; 18; 19; 20; 21]. Volatile compound composition might be due to seasoning, smoking or the reactions between lipids, proteins, and carbohydrates caused by microbial or endogenous enzymes [22]. Lipolysis and proteolysis are essential biochemical reactions for volatile compound development as they provide precursors, free amino acids, and fatty acids, which will be further degraded to produce aroma compounds [23; 24; 25]. Nitrates/nitrites play a significant role in the development of the unique cured meat flavor; however, the mechanism is not fully understood. When nitrites are bound to sulfur-containing amino acids of meat proteins, SH-residues with a specific aroma and flavor are formed and contribute to the unique flavor of cured meat. To the best of our knowledge, few studies have examined the effect of nitrate/nitrite reduction on the aroma development in meat products. The trend in volatile compound studies is to report the changes produced in the volatile profile due to different factors (e.g., salt reduction, fat content) and the identification of hundreds of volatile compounds [20; 26]. The study by [PERSON] et al. [27] reported an effect on volatile compound formation in dry sausages with reduced nitrate/nitrite addition. The sausages with reduced curing agents contained the highest amounts of volatile compounds derived from carbohydrate fermentation and amino acid degradation reactions, probably produced by the increased growth of Gram-positive catalase-positive cocci and _Enterobacteriaceae_.