## 3 Results and Discussion
### Oxidative Stability and Microbiological Safety During Storage  
The oxidative stability of both full-fat soy (FFS) and expanded soybean cake (ESC) was monitored over a 6-month storage period under ambient, light-protected conditions (Table 9). ESC consistently demonstrated superior oxidative stability compared to FFS throughout storage. In FFS, Totox index values progressively increased from 5.84 at month 1 to 12.70 after 6 months, indicating gradual lipid oxidation during storage. In contrast, ESC maintained low Totox values, ranging from 2.65 to 7.91, even after 6 months, confirming the stabilizing effect of partial fat removal. These results align with previous findings that reduced lipid content enhances oxidative stability in soy-based products [48; 49]. Peroxide value (PV), anisidine value (ANV), and acid value (AV) followed similar trends, with ESC consistently showing lower values compared to FFS (\(p<0.05\)). The reduction of free fatty acids (FFA) during processing further contributed to ESC's superior oxidative performance. Soybean oil extracted during ESC production exhibited moderate oxidative stability. While Totox values remained acceptable up to 3 months (8.80-9.60), they increased to \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Characteristic**} & \multicolumn{3}{c}{**FFS**} & \multicolumn{3}{c}{**ESC**} & \multicolumn{3}{c}{**Oil**} \\ \cline{2-11}  & **1** & **3** & **6** & **1** & **3** & **6** & **1** & **3** & **6** \\ \hline \multicolumn{11}{c}{AV} \\ (mg g\({}^{-1}\) KOH) & \(2.03\pm 0.01\)\({}^{\text{a,b}}\) & \(3.10\pm 0.02\)\({}^{\text{b}}\) & \(4.40\pm 0.03\)\({}^{\text{c}}\) & \(1.37\pm 0.01\)\({}^{\text{a}}\) & \(1.83\pm 0.01\)\({}^{\text{a}}\) & \(3.25\pm 0.02\)\({}^{\text{b}}\) & \(0.64\pm 0.00\)\({}^{\text{a}}\) & \(2.10\pm 0.01\)\({}^{\text{a}}\) & \(13.8\pm 0.90\)\({}^{\text{b}}\) \\ \hline \multicolumn{11}{c}{FFA (\%)} & \(1.33\pm 0.01\)\({}^{\text{a}}\) & \(2.67\pm 0.02\)\({}^{\text{b}}\) & \(3.46\pm 0.02\)\({}^{\text{c}}\) & \(0.89\pm 0.01\)\({}^{\text{a}}\) & \(1.48\pm 0.01\)\({}^{\text{b}}\) & \(2.01\pm 0.01\)\({}^{\text{c}}\) & \(0.95\pm 0.01\)\({}^{\text{a}}\) & \(1.15\pm 0.01\)\({}^{\text{a}b}\) & \(1.50\pm 0.01\)\({}^{\text{b}}\) \\ \hline \multicolumn{11}{c}{PV} \\ (meq Q\({}_{2}\) kg\({}^{-1}\)) & \(2.62\pm 0.02\)\({}^{\text{a,b}}\) & \(3.25\pm 0.02\)\({}^{\text{b}}\) & \(5.70\pm 0.04\)\({}^{\text{c}}\) & \(1.13\pm 0.01\)\({}^{\text{a}}\) & \(1.48\pm 0.01\)\({}^{\text{a}}\) & \(2.15\pm 0.01\)\({}^{\text{a,b}}\) & \(4.20\pm 0.03\)\({}^{\text{a}}\) & \(4.50\pm 0.03\)\({}^{\text{a}}\) & \(4.80\pm 0.03\)\({}^{\text{a}}\) \\ \hline \multicolumn{11}{c}{ANV} \\ \(0.61\pm 0.00\)\({}^{\text{a}}\) & \(0.95\pm 0.01\)\({}^{\text{a,b}}\) & \(1.30\pm 0.01\)\({}^{\text{b}}\) & \(0.38\pm 0.00\)\({}^{\text{a}}\) & \(1.30\pm 0.01\)\({}^{\text{b}}\) & \(3.61\pm 0.02\)\({}^{\text{c}}\) & \(0.40\pm 0.00\)\({}^{\text{a}}\) & \(0.60\pm 0.00\)\({}^{\text{a}}\) & \(0.90\pm 0.01\)\({}^{\text{a}}\) \\ \hline \multicolumn{11}{c}{Totox index} \\ \(5.84\pm 0.04\)\({}^{\text{a,b}}\) & \(7.45\pm 0.05\)\({}^{\text{a,b}}\) & \(12.7\pm 0.8\)\({}^{\text{b}}\) & \(2.65\pm 0.02\)\({}^{\text{a}}\) & \(4.25\pm 0.03\)\({}^{\text{a}}\) & \(7.91\pm 0.05\)\({}^{\text{a,b}}\) & \(8.80\pm 0.06\)\({}^{\text{a}}\) & \(9.60\pm 0.06\)\({}^{\text{a}}\) & \(10.5\pm 0.07\)\({}^{\text{a}}\) \\ \hline \hline \end{tabular}  
*—small superscript letters (a, b, c) indicate significant differences between storage months for FFS, ESC, and oil, according to [PERSON]’s HSD test (\(p<0.05\)). AV—acid value, FFA—free fatty acids, PV—peroxide value, ANV—anisidine value.  
\end{table} 
Table 9: Oxidative stability parameters of full-fat soy (FFS), expanded soybean cake (ESC), and extracted soybean oil during 6-month storage. 10.5 by month 6, suggesting limited storage stability without antioxidant supplementation. These results underscore the need for additional stabilization strategies for isolated soybean oil if extended shelf-life is required.