## 3 Results and Discussion
### Physicochemical and Microbiological Parameters  
The colour of fresh meat and meat products is one of the most important quality properties affecting consumer choice, for which reason the colour stability of such products during storage and retail display is crucial for meat manufacturers and retailers [41]. The evaluation of colour indicators is explained in Table 5. The L* values (indicating lightness) of samples with sumac treatment (T1, T2 and T3) were significantly lower (\(p<0.05\)) in comparison with control samples. Lightness reduction was correlated with the increasing percentage of sumac treatment. Sumac had a significant (\(p<0.05\)) effect on the redness (a*) values of carp muscle. The redness values of T1, T2 and T3 increased with the elevation in the sumac ratio. No significant differences were observed in redness indictors between samples at 24 h and 72 h. The red-like pigmentation of sumac was attributed to anthocyanins, which are the main phenolic compound in sumac. Hydroxyphenyl-pyranoanthocyanins are found in sumac and wine and are responsible for their pigmentation capacity [42]. The contribution of the main pigment in sumac (anthocyanins) to the red coloration of the product seems to be complex in nature because it is affected by the pigment's heat stability, the temperature regime, the concentration and pH [43]. Sumac did not influence yellowish values (b*) except in T3, in which the b* values increased significantly (\(p<0.05\)) after 24 h of storage. [PERSON] and [PERSON] [44] indicated that sumac may be exposed to some browning coloration reaction due to the effect of air temperatures. \begin{table}
\begin{tabular}{l c c c c} \hline
**Parameters** & \multicolumn{4}{c}{**Sumac Concentration**} \\ \hline
**In Raw State** & **0\% (T0)** & **0.5\% (T1)** & **1.5\% (T2)** & **2.5\% (T3)** \\ \hline overall acceptability & 82.43 \(\pm\) 24.10  & 40.86 \(\pm\) 29.34  \\ colour acceptability & 85.00 \(\pm\) 13.99  & 45.14 \(\pm\) 26.30  \\ natural fishy colour & 91.43 \(\pm\) 13.16  & 57.71 \(\pm\) 26.57  \\ sour colour & 6.86 \(\pm\) 8.95  & 46.14 \(\pm\) 28.21  \\ masking of fish odour & 3.14 \(\pm\) 7.08  & 57.29 \(\pm\) 35.30  \\ degree of muscle juice release & 3.14 \(\pm\) 5.11  & 22.14 \(\pm\) 28.01  \\ degree of tenderness & 24.86 \(\pm\) 31.88  & 53.71 \(\pm\) 24.74  \\ overall acceptability & 82.43 \(\pm\) 24.10  & 40.86 \(\pm\) 29.34  \\ \hline After Heat Treatment & & & & \\ \hline overall acceptability & 78.43 \(\pm\) 26.41 & 74.14 \(\pm\) 25.21 & 49.71 \(\pm\) 14.23 & 45.29 \(\pm\) 24.92 \\ colour acceptability & 75.71 \(\pm\) 31.65 & 71.57 \(\pm\) 31.65 & 49.71 \(\pm\) 17.09 & 46.14 \(\pm\) 28.48 \\ natural fishy colour & 88.71 \(\pm\) 13.50  & 41.71 \(\pm\) 18.64  & 72.14 \(\pm\) 14.53 [FOOTNOTE:]Footnote : Values in the same row are significantly (\(p<0.05\)) different between sumac concentrations, \(The results of water activity, pH value and microorganism count are shown in Table 6. Regarding water activity, we did not find any statistically significant differences (\(p>0.05\)) between the measured values as a function of the concentration of sumac product or as a function of the storage time of the samples. We can therefore conclude that in terms of this parameter and its importance on the growth and multiplication of contaminating microorganisms, the conditions were practically the same in all fillet samples. A different situation was found for the pH values. Given the pH value of the aqueous sumac spice leachate used in this experiment of 2.85, there was a statistically significant (\(p<0.05\)) acidification of the fillets at the highest concentration of sumac spice used (T3) at both 24 and 72 h after application. A similar trend of decrease in pH value at 24 h after application was also observed for the 1.5% concentration (T2); however, after 72 h of storage the pH value of this sample was higher than 6.00. The pH value of fillets with 0.5% addition of sumac spices (T1) was practically the same during the experiment.