# Quality of Pork Loin Subjected to Different Temperature-Time Combinations of Sous Video Cooking
## 3 Results and Discussion
### Instrumental Colour Measurement  
The colour of meat is an important criterion for its quality evaluation by the consumer, and the cooked meat colour can have a decisive effect on the product acceptance [40; 61]. While in some groups of consumers/countries, consumption of rare or medium-rare meat is a matter of tradition or preference, in other groups/countries the reddish or pinkish colour of meat may be perceived as an undercooked state of product [62; 63]. In the present study, when determining the colour of sons wide-coked pork in the CIE \(L^{\star}a^{\star}b^{\star}\) system (Table 3), it was shown that the lightness (\(L^{\star}\)) of raw meat was 52.16, while that of heated meat was from 66.33 (cooking at 57 \({}^{\circ}\)C/3.5 h) to 71.98 (cooking at 60 \({}^{\circ}\)C/3.5 h). Cooked samples did not differ significantly in terms of their lightness and no significant effect of temperature and heating time as well as their interaction on the lightness (\(L^{\star}\)) of the examined pork loin was found. Likewise, no significant differences in \(L^{\star}\) values for lamb sous vide cooked at 60/70/80 \({}^{\circ}\)C were reported by [PERSON] et al. [38]. In addition, [PERSON] et al. [38] and [PERSON] et al. [64] observed slightly higher \(L^{\star}\) values for lamb and pork, respectively, cooked at lower temperatures, which they explained by the differences in water presence on the meat surface. [PERSON] et al. [22] noted an increase in the \(L^{\star}\) value of pork ham when the heating temperature increased from 61 \({}^{\circ}\)C to 71 \({}^{\circ}\)C and attributed this observation to the differences in moisture content in samples which affects the depth of light penetration in the tissue and thus the colour of the meat surface [65], as well as an increased protein denaturation and aggregation at higher temperatures, which leads to increased light scattering and increases the lightness of the meat [66]. In our study, higher cooking temperatures led to a slight reduction in meat redness (\(a^{\star}\)), which was also observed in other studies [21; 38; 67; 68]. The meat redness was affected by the cooking temperature (\(p<0.001\)); however, the significant differences were observed mainly between some of the samples cooked at 61 \({}^{\circ}\)C and 57 \({}^{\circ}\)C. The share of redness in the overall colour of heated meat products is inversely related to the degree of myoglobin denaturation, and as the cooking temperature increases, the degree of myoglobin denaturation increases causing the reduction in meat redness [4; 38]. As a consequence, the pork loin samples cooked at a lower temperature showed a more intense red colour (higher \(a^{\star}\) values) than those cooked at a higher temperature, indicating higher myoglobin degradation with increasing cooking temperature. In addition, [PERSON] et al. [67] observed that sous vide-coked meat showed a more reddish colour than meat cooked by other methods and suggested that packaging used in sous vide treatment could protect myoglobin from degradation. It was confirmed by [PERSON] et al. [64], who showed that the \(a^{\star}\) value was higher for pork cooked with sous vide method at 60 \({}^{\circ}\)C and 80 \({}^{\circ}\)C than for meat cooked traditionally in water. It was noted in the present experiment that the \(b^{\star}\) values of heat-treated samples were higher than those of raw meat; however, no significant differences were observed between cooked samples. Contrary to our results, higher \(b^{\star}\) values with increasing temperature and time of lamb loin sous vide cooking have been reported in the study by [PERSON] et al. [38], but in that study temperatures 60-80 \({}^{\circ}\)C and times 6-24 h were applied as cooking parameters. In the literature, the increase in yellowness values of meat upon cooking is attributed to the formation of metmyoglobin and its further heat denaturation, giving meat a brownish colour [38; 40; 62]. According to [PERSON] et al.