## 3 Results
### The Effect of Storage on the Sensory Quality of Very-Low-Sugar Apple Jams with Added SGs
The pH value in the evaluated jams was related to the level of SG substitution (r = 0.64, \(p<0.001\)) and the storage time (3, 6 months) (r = 0.64, \(p<0.05\)). \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Color (L*a*b*)**} & \multicolumn{4}{c}{**Addition of SGs (\%) to Very-Low-Sugar (VL) Jams**} \\ \cline{2-5}  & **0** & **30** & **50** & **80** \\ \hline \multicolumn{5}{c}{Color change after 6 months of storage **} \\ \hline L* & 32.38 \(\pm\) 0.01 & 33.18 \(\pm\) 0.01 & 33.63 \(\pm\) 0.01 & 33.9 \(\pm\) 0.2 \\ \hline \(\Delta\)L & \(-\)0.22 & \(-\)0.71 & \(-\)0.47 & \(-\)0.63 \\ \hline a* & \(-\)0.15 \(\pm\) 0.08 & \(-\)0.32 \(\pm\) 0.22 & \(-\)0.36 \(\pm\) 0.16 & \(-\)0.4 \(\pm\) 0.09 \\ \hline \(\Delta\)a & 0.24 & 0.09 & 0.08 & 0.08 \\ \hline b* & 15.47 \(\pm\) 0.02 & 15.55 \(\pm\) 0.13 & 15.84 \(\pm\) 0.05 & 15.9 \(\pm\) 0.04 \\ \hline \(\Delta\)b & \(-\)0.3 & \(-\)0.55 & \(-\)0.47 & \(-\)0.89 \\ \hline C & 15.76 & 15.54 & 15.83 & 15.89 \\ \hline \(\Delta\)C & 0.38 & 0.56 & 0.48 & 0.89 \\ \hline (\(\Delta\)E) & 0.38 & 0.9 & 0.67 & 1.09 \\ \hline \end{tabular}  
* Color changes compared to jam with only sugar (control sample) and ** color changes compared to jam at the beginning of storage. Interpretation of color difference: 0 \(<\Delta\)E \(<\) 1, the difference in color is visually nonrecognizable by a standard observer; 1 \(<\Delta\)E \(<\) 2, the difference is visually recognizable only by an experienced observer; and 2 \(<\Delta\)E \(<\) 3.5, the difference can be visually recognized by an inexperienced observer.  
\end{table} 
Table 4: _Cont._A similar relationship was found for acidity. With increasing SG addition, tittatable acidity and the acidity expressed as malic acid increased (r = 0.74 and r = 0.91, \(p<0.05\), respectively). The same relationship was found after storage for 3 and 6 months (r = 0.76 and r = 0.94, \(p<0.05\), respectively). The total acidity expressed as malic acid content depends on the initial content of organic acids. In the raw apples used to prepare the jam, it was 0.42 g of malic acid per 100 g; after processing, this increased in the control sample (Table 5). The total acidity of the very-low-sugar apple jams decreased significantly only in the variant with sugar content, suggesting that substitution with steviol glycosides did not consistently stabilize this parameter. This could impact the product's overall quality and shelf life, as acidity is critical in preventing microbial growth and ensuring product safety during storage. The Effect of Storage on the Microbiological Quality of Very-Low-Sugar Apple Jams with Added Steviol Glycos  
The microbiological quality assessment carried out at the beginning of the storage cycle and after storage for 3 and 6 months did not show the presence of _Listeria monocytogenes_ and coagulase-positive staphylococci (Table 6). The content of yeasts and molds and the total number of microorganisms (OLD at 30 \({}^{\circ}\)C) were satisfactory, below 10. Therefore, the microbiological quality of the jams was good and did not change during storage for 3 and 6 months, regardless of the level of sugar substitution with steviol glycosides.