# Is Prolonged Ageing a Necessity for Improving the Quality of Sous-Vide Cooked Beef?
## 3 Results and Discussion
### The Influence of Ageing on Uncooked Bef  
The impact of wet ageing on the physico-chemical parameters of the steaks is presented in Table 2. Ageing time did not affect meat pH and thaw loss (\(p\) > 0.05). The \(L^{*}\) values of the beef surface increased during ageing, where 4 d aged samples were darker than 21 d aged ones (\(p\) < 0.05). Significant differences in the colour of the cross-section area between samples aged 4, 14 and 21 days were also noted in terms of lightness and redness. The values of \(L^{*}\) measured on the cross-section area of the beef samples aged for 4 days were lower than those aged for 21 days (\(p\) < 0.05), and those samples showed lower \(a^{*}\) values than 14 d and 21 d aged samples (\(p\) < 0.05). Values of \(b^{*}\), \(C^{*}\) and \(h^{\circ}\) were not affected (\(p\) > 0.05) by the ageing time in either the surface or cross-section area colour parameters of the steaks. As reported by [PERSON] et al. [4], the pH of meat might increase during wet ageing, however, the most pronounced increase was noted after 8 weeks of ageing. When meat ageing is conducted for a shorter period, the changes might not be so obvious. [PERSON] et al. [7] noted similar pH values in beef aged 3, 7 and 14 days; moreover, the samples aged 7, 14 and 21 days did not differ in pH either. Generally, the pH increase might be explained by the accumulation of protein degradation products. On the other hand, in vacuum packages, lactic acid bacteria can grow and produce acids, which affect meat pH. This might alleviate the effect of the alkalisation caused by proteolytic breakdown, which explains the lack of changes in beef pH during ageing in the present study. Generally, meat colour is the first and the most important visual attribute based on which consumers evaluate the quality of meat [39]. Redness (\(a^{*}\)) values higher than 14.5 were proposed as an indicator of consumer acceptance of beef [40]. In the present study, 14 d and 21 d aged uncooled beef steaks showed \(a^{*}\) values (measured on the beef surface) above this threshold, whereas \(a^{*}\) values of 4 d aged samples were slightly below \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Attribute**} & \multicolumn{4}{c}{**Ageing Time (days)**} & \multirow{2}{*}{**Significance**} \\ \cline{2-2} \cline{4-5}  & **4** & **14** & **21** \\ \hline pH & 5.55 \(\pm\) 0.01 & 5.55 \(\pm\) 0.01 & 5.56 \(\pm\) 0.02 & NS \\ Thaw loss (\%) & 8.3 \(\pm\) 0.5 & 8.0 \(\pm\) 0.5 & 8.2 \(\pm\) 0.5 & NS \\ Surface colour & & & & \\ \(L^{*}\) & 30.0 \({}^{\text{b}}\)\(\pm\) 0.5 & 31.2 \({}^{\text{ab}}\)\(\pm\) 0.4 & 32.3 \({}^{\text{a}}\)\(\pm\) 0.5 & *** \\ \(a^{*}\) & 14.2 \(\pm\) 0.4 & 14.6 \(\pm\) 0.4 & 15.1 \(\pm\) 0.4 & NS \\ \(b^{*}\) & 4.85 \(\pm\) 0.15 & 5.23 \(\pm\) 0.18 & 5.35 \(\pm\) 0.20 & NS \\ \(C^{*}\) & 15.0 \(\pm\) 0.4 & 15.5 \(\pm\) 0.4 & 16.0 \(\pm\) 0.5 & NS \\ \(h^{\circ}\) & 18.9 \(\pm\) 0.3 & 19.8 \(\pm\) 0.5 & 19.5 \(\pm\) 0.5 & NS \\ Cross-section colour & & & & \\ \(L^{*}\) & 30.7 \({}^{\text{b}}\)\(\pm\) 0.4 & 31.9 \({}^{\text{ab}}\)\(\pm\) 0.5 & 32.9 \({}^{\text{a}}\)\(\pm\) 0.4 & * \\ \(a^{*}\) & 15.5 \({}^{\text{b}}\)\(\pm\) 0.4 & 17.4 \({}^{\text{a}}\)\(\pm\) 0.5 & 17.29 \({}^{\text{a}}\)\(\pm\) 0.28 & * \\ \(b^{*}\) & 4.36 \(\pm\) 0.17 & 5.39 \(\pm\) 0.27 & 5.10 \(\pm\) 0.16 & NS \\ \(C^{*}\) & 16.1 \(\pm\) 0.4 & 18.2 \(\pm\) 0.5 & 18.0 \(\pm\) 0.3 & NS \\ \(h^{\circ}\) & 15.6 \(\pm\) 0.3 & 16.8 \(\pm\) 0.7 & 16.3 \(\pm\) 0.3 & NS \\ \hline \hline \end{tabular}  
* Data are presented as the mean \(\pm\) standard error of the mean (SEM). \({}^{\text{a}}\)\({}^{\text{b}}\) mean values in rows with different letters differ significantly at \(p\) < 0.05, NS--non-significant differences (\(p\) > 0.05),
* differences significant at \(p\) < 0.05; **
* differences significant at \(p\) < 0.001; \(L^{*}\)—lightness, \(a^{*}\)—redness, \(b^{*}\)—yellowness, \(C^{*}\)—chroma, \(h^{*}\)—blue angle.  
\end{table} 
Table 2: The effect of wet ageing on the quality of uncooled _longissimus lumborum_ steaks. the threshold.