# Quality of Sous Vide-Cooked Pork Loin Stored in Refrigerated Conditions
## 3 Results and Discussion
### Colour  
Visual appearance, including colour, is the first feature of a cooked meat assessed by the consumer and often has a decisive effect on the acceptance or rejection of the product. The colour of the meat is determined by the light reflecting, scattering, or absorbing [9; 49]. The colour of cooked meat differs from that of the raw meat and the change can be attributed to the changes in moisture content [49; 50], protein denaturation and aggregation [51], oxidation, enzymatic and nonenzymatic browning [52], and myoglobin denaturation [1; 13; 53] as well metmyoglobin formation and its further denaturation [53; 54; 55]. The results of the colour coordinate measurements of raw and cooked and then stored pork loin using the CIE \(L^{\star}\)\(a^{\star}\)\(b^{\star}\) colour space are presented in Table 1. All lightness (\(L^{\star}\)) values observed for cooked samples (65.23-75.40) were higher than that of raw meat (60.11), which indicates that the colour of meat lightened as a result of heat treatment. Lightness of stored meat samples was significantly affected by treatment and time of storage (both \(p<0.001\)), while no significant effect of their interaction was demonstrated. Increasing \(L^{\star}\) values were noted with increasing time of storage but the effect of treatment was not so clear since the highest \(L^{\star}\) values were observed for samples cooked at 60 \({}^{\circ}\)C/4 h. Redness (\(a^{\star}\)) values of stored pork loin samples were also significantly affected by treatment and time of storage (both \(p<0.001\)), but the effect of their interaction was not significant. It  
Figure 1: Oxidative changes in sons wide-cooked pork loin stored in refrigerated conditions (mean \(\pm\) SD). was shown that with an increase in the heating temperature and the extended storage time, \(a^{*}\) values decreased, which means that the meat became less red due to the higher degree of myoglobin degradation [52]. Redness values of the sample cooked at the lowest temperature (8.07-8.36) remained very close to the value measured for raw meat (8.65) throughout the entire storage period. The lowest \(a^{*}\) values were noted for the sample cooked at the highest temperature (6.38-6.67). Significant changes in \(a^{*}\) value during storage were noted only for samples cooked at 60 \({}^{\circ}\)C/4 h and at 61 \({}^{\circ}\)C/4 h.  
Yellowness (\(b^{*}\)) values of stored meat samples (12.28-14.29) were distinctly higher that \(b^{*}\) value measured for raw meat (5.01). There was a significant effect of treatment conditions on the value of the \(b^{*}\) parameter (\(p<0.001\)) of stored samples, but no significant effects of storage time and the interaction between treatment and storage time were demonstrated. The lowest \(b^{*}\) values were observed for the sample cooked at 57 \({}^{\circ}\)C/5.5 h and the highest \(b^{*}\) values were noted for the samples cooked at the temperatures 61 \({}^{\circ}\)C/4 h and 63 \({}^{\circ}\)C/4 h.  
The colour is influenced by oxidative processes related mainly to the oxidation of myoglobin, which leads to changes in the tone and intensity of meat redness [13; 25; 49; 52; 56]. [PERSON] et al. [57] did not observe significant differences in colour parameters \(L^{*}\), \(a^{*}\) and \(b^{*}\) of pork loin cooked to the same internal temperature by steaming, vacuum cooking, and sous vide cooking, but they differed from those parameters recorded for meat cooked in the oven. [PERSON] et al. [58] reported significantly higher \(b^{*}\) values of sous vide-cooked pork meat compared to meat cooked traditionally, but no significant differences were noted for \(L^{*}\) and \(a^{*}\) values. Saturation (chroma, C*) and tone (hue angle, \(h^{\circ}\)) of colour are related to the myoglobin concentration in meat and its degree of denaturation.