## 3 Results and Discussion
### Lipid Oxidation and \(pH\)  
Figure 1 shows the TBARS values of ground beef treated with MOLP during cold storage. The inclusion of MOLP decreased the TBARS values from days 0 to 15. The decrease of TBARS in treated ground beef might be due to polyphenols in MOLP, which adsorbs and neutralises free radicals, leading to the prevention of fat oxidation [46]. Fat oxidation and generation of volatile metabolites might be attributed to the increase in TBARS of ground beef during storage days [47, 48]. However, samples treated with MOLP displayed delay in lipid oxidation at the end of storage day compared to the untreated sample (control). Several studies have documented the positive relationship between reduced lipid oxidation and polyphenol content or antioxidant activity of plant extracts [1, 49]. The association of natural substances such as polyunsaturated fatty acids with catalysts such as iron ion from the tissue of ground beef might have contributed to high values of TBARS in control sample throughout the storage days [50]. Such storage will ultimately promote the breakdown of heme compounds, thereby liberating the low-molecular-weight iron compounds in ground beef that are assumed to be accountable for lipid oxidation. [PERSON] et al. [51] reported similar results, wherein the inclusion of pre-blended carnosine decreased the TBARS values of ground buffalo meat during storage days. Moreover, the same authors reported that certain bacteria such as _Pseudomonas ovals_, _Microoccus freudenseichia_, as well as strains of _Streptomyces_ also contribute to lipid oxidation by producing compounds such as aldehydes, ketones, peroxides, and carbonyls or other similar compounds. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Storage Time (Days)**} \\ \hline
**Parameters** & **Formulation (\%)** & **0** & **5** & **10** & **15** \\ \hline TPC (mg GAE/g) & F0 & 15.21 \(\pm\) 0.08 \({}^{\text{\text{\text{\text{\text{\text{\text  
There were significant differences of pH values (\(p\) < 0.05) in all samples throughout storage days, except at day zero. Between days 0, 5, 10, and 15, the pH increased from 5.49 to 5.61, 5.74 to 5.44, 6.48 to 5.85, and 6.87-6.28, respectively, during storage days, as indicated in Figure 2. The high pH values of ground beef during storage might be attributed to the proliferation of Gram-negative bacteria such as _Pseudomonas, Moraxella_, and _Acinetobacter_, which resulted in the accumulation of metabolites [52]. Moreover, the rise of pH values throughout cold storage might have been due to bacteria utilising amino acids after the loss of stored glucose during the breakdown of proteins. This results in the build-up and generation of ammonia formation, which gives rise to the pH values of ground beef throughout the cold storage days [53]. According to [PERSON] et al. [54], meat with a pH greater than normal of 5.8 is more prone to spoilage and results in lower shelf-life. Moreover, the higher meat pH results in less myoglobin, with the meat muscle becoming firm due to the high water holding capacity. Similar results were reported by [PERSON] and [PERSON] [55], wherein the incorporation of pre-blendedtocopherol acetate increased the pH of ground chevon meat during refrigerated storage. [PERSON] et al. [56] also reported similar findings of a grad  
Figure 1: Effects of MOLP on thiobarbituric acid reactive substances (TBARS) of ground beef stored at \(4\pm 1\)\({}^{\circ}\)C for 15 days. Means with different superscripts show significant difference among treatments within same storage day at \(p\leq 0.05\). F0 (100% ground beef), F1 (0.2%), F2 (0.4%), F3 (0.6%), and F4 (0.8%) _Moring oleifera_ leaves powder. Figure 2: Effects of MOLP on pH of ground beef stored at \(4\pm 1\)\({}^{\circ}\)C for 15 days. Values are expressed as mean \(\pm\) standard deviation. Means with different superscripts show significant differences among treatments within same storage day at \(p\leq 0.05\).