# Influence of LAB Fermentation on the Color Stability and Oxidative Changes in Dry-Cured Meat
## 4 Discussion
High TBARS values observed after 6 months of aging indicate a high content of oxidation products and may also be attributable to the reaction of MDA with amino acids, sugar, nitrates, and nitrites in the complex ([PERSON] et al. [35]). Several authors reported a limiting effect of LAB strains on TBARS in the aging process of various meat products, but it was observed in this study, and even LOCK and BB tests showed slightly higher TBARS values than the control in the 6 th month. Over time, TBARS values decreased in all variants, finally reaching (in the 12 th month) the value of 1.191 mg MDA/kg in trial C and higher values, i.e., 1.166, 1.193, and 1.155 for LOCK, BB, and BAUER samples, respectively. Several authors reported a high increase in TBARS values between 4 and 6 months of aging [38; 43] in fermented loins, necks, or sausages, followed by a decrease to a level similar to that recorded in the present study. Generally, the oxidation of fats and proteins in food products follows a common mechanism as, in both cases, the mechanism is a chain reaction of initiation, transmission, and termination. These reactions are induced by active substances, such as reactive oxygen species (ROS) and reactive nitrogen species or indirectly by oxidative stress secondary products (such as already oxidized lipids or carbohydrate oxides). In particular, ROS can oxidize amino acid side chains and the protein backbone, leading to protein fragmentation or protein-protein crosslinking. In addition, oxidation processes, especially of proteins, can be catalyzed by metal ions (Fe\({}^{2+}\), Cu\({}^{2+}\), Mn\({}^{2+}\)), such as heme ions released during heme decay, in myoglobin [14; 41]. Due to the oxidation of the protein molecule, its hydrophobicity increases, among others, as a result of changes in its secondary and tertiary structures and exposure to the hydrophobic groups on the protein surface [44]. Therefore, in the present study, surface hydrophobicity of proteins from the fermented pork loins during aging was determined to estimate oxidative changes. After 6 months of aging, the surface hydrophobicity of samples inoculated with LAB was significantly (\(p<0.05\); Figure 1) higher than that of samples subjected to spontaneous fermentation using environmental microflora. This is probably due to the relaxation of the protein structure by the action of oxidative factors. In the natural structure of proteins, hydrophilic amino acid residues are exposed to the water phase, whereas hydrophobic residues are usually found in molecules. The structure of proteins unfolds due to oxidation, revealing hydrophobic amino acids in peptide chains that were previously hidden in proteins, thereby increasing the surface hydrophobicity of proteins [44]. Indeed, surface hydrophobicity corresponds to the TBARS score, which was higher for LAB samples (Table 3), indicating the intensification of fat oxidative processes. With time, a decrease in the HS content was observed in all samples, except for BAUER samples. The reduction in surface hydrophobicity may also be due to the action of proteases. During the fermentation process, meat proteins undergo gradual time-dependent proteolysis, gradually breaking down long-chain fragments into small peptides, and thus may have a lower number of hydrophobic binding sites than larger peptides [45]. A previous study reported that LAB strains affect the degree of proteolysis during 360-day aging [46]. In addition, in the peptidom approach, the highest influence of LAB on the meat proteome was observed in particular after 180 (BB12 and BAUER) and 270 (C and LOCK) days of aging in the range of sarcoplasm proteins [18]. These authors also emphasized the slight influence of the LOCK strain on changes in the myofibrillar protein fraction resulting from proteolysis compared with the control, regardless of the time criterion, whereas BAUER samples were the most different [18]. The decrease in HS values observed in this study may also be due to changes in free SH groups.