Effect of High-Pressure Processing and Long-Time Storage on Color, Lipid Oxidation, and Free Amino Acids Profile of Beef  
[PERSON]  
1 Department of Food Technology and Assessment, Warsaw University of Life Sciences-SGGW, 16e 180 wowowoynowska Street, 02-787 Warsaw, Poland; [EMAIL_ADDRESS] (L.A.); [PERSON]L_ADDRESS] (L.A.C. ); [EMAIL_ADDRESS] (D.P. ); [PERSON]_ADDRESS] (D.S. );  
[PERSON]  
1 Department of Food Technology and Assessment, Warsaw University of Life Sciences-SGGW, 16e 180 wowoynowska Street, 02-787 Warsaw, Poland; [PERSON]IL_ADDRESS]l (L.A.); [PERSON]L_ADDRESS]l (L.A.C. ); [PERSON]_ADDRESS]l (D.P. ); [PERSON]_ADDRESS] (D.P. ); [PERSON]_ADDRESS] (D.P. ); [PERSON]_ADDRESS] (D.S. ); [PERSON]SS] (M.R. ); [PERSON]SS] (M.B.) [PERSON]  
1 Department of Food Technology and Assessment, Warsaw University of Life Sciences-SGGW, 16e 180 wowoynowska Street, 02-787 Warsaw, Poland; [PERSON]SS] (L.A.); [PERSON]S] (L.A.C. ); dorota_  
characteristics (color, texture parameters, and water-holding capacity). The HPP treatment influences meat's free amino acids composition [4; 5] and accelerates lipid oxidation of meat fat, leading to rancidity and off-flavor development [6]. The effect of HPP treatment on raw fresh meat color is due to the denaturation of globin, resulting in the displacement (or release) of the heme group and also protein coagulation, which is manifested by, among other things, the loss of solubility of sarcoplasmic and/or myofibrillar proteins [7]. [PERSON] et al. [8] emphasized that higher pressure used in beef during HPP decreased the myoglobin content because of its denaturation. In the literature [7; 9], the most often reported modification of the raw fresh meat color treated by HPP is an increase in lightness (L*), which starts to occur at pressures higher than 200 MPa. In the studies of [PERSON] et al. [10], the authors noted that applying a pressure of 300 MPa to dark-cutting beef increased its redness and slowed down the process of color darkening. Meat surface discoloration caused by HPP could be significant and occur after just 1 min of exposure to 400 MPa, but is less dependent on the duration of HPP treatment [11]. According to [PERSON] et al. [12], HPP-treated (600 MPa) ground beef is most commonly used in the HoReCa industry, where this meat is usually further processed (e.g., cooked) to reduce the discoloration resulting from HPP treatment. The HPP increases the susceptibility of meat lipids to attack by molecular oxygen, leading to the initiation of the oxidation process [13]. In this case, adverse effects of the accelerating oxidation process are not visible immediately after HPP treatment but only after subsequent storage under cooling conditions, depending to a greater extent on the working pressure than on the time of its exposure [14; 15]. The critical pressures affecting the oxidation process can vary depending on the food type, and the most common range is 300-600 MPa [13]. Most studies indicate the faster oxidation of food samples after exposure to HPP [9; 16]. According to [PERSON] et al. [7], the broader application of the HPP technique in the meat industry may be determined by the qualitative and quantitative changes in the lipids generated by it. The negative impact of the HPP treatment on fat oxidation in meat can be reduced by vacuum packaging this raw material before pressurization [17]. Unlike lipid oxidation, the processes of food protein oxidation under the influence of HPP gained the interest of researchers much later. Even though the mechanisms and reaction paths of lipid and protein oxidation are not the same, their common feature is their susceptibility to similar pro- and antioxidant factors [1; 4; 7; 14]. The protein modifications under HPP are complex and result from conformational and chemical changes. This may also result in changes in the profile of amino acids.