## 3 Results and Discussion
### Physical and Chemical Analysis of Grapes and Wines
#### 3.1.2 Physicochemical Analysis of the Three Different Groups of Petit Manseng Wines  
There were significant differences in physicochemical indexes among the three different groups of Petit Manseng wine samples. The physicochemical indexes of wines made from grapes with different levels of gray mold infestation are shown in Table 3. These are important indicators of wine quality. There were statistically significant differences between the groups in alcohol, volatile acid, free sulfur, total sulfur, and glycerol content (\(p\) < 0.05). There were no statistically significant differences between the groups in pH or total acid content (\(p\) > 0.05; Table 3). The basic physicochemical indexes of the sweet white wines brewed from the three grape groups met the requirements of the International Code of Oenological Practices (Table 3). The alcohol content ranged from 12.03% to 12.27% (\(v\)/\(v\)), with the highest alcohol content seen in group C and the lowest in group A. There was no significant difference in total acid content between Group A (7.29 \(\pm\) 0.06 b) and Group B (7.34 \(\pm\) 0.07 b), but it was significantly lower than that in Group C (7.61 \(\pm\) 0.04 a). The volatile acid content (acetic acid) ranged from 0.69 to 0.86 g/L. The glycerol content increased significantly from Group A (8.28 \(\pm\) 0.04 c) to Group C (15.69 \(\pm\) 0.07 a). Altering glycerol content may considerably affect the body and alcohol content of a wine [19]. The glycerol content of the various wine \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Grape Samples** & **PHT** & **Total Acid (g/L)** & **Total Sugars (g/L)** & **Glycerol (g/L)** \\ \hline A group & 3.37 \(\pm\) 0.1 a & 7.48 \(\pm\) 0.06 a & 300.42 \(\pm\) 1.61 c & 0.44 \(\pm\) 0.01 c \\ B group & 3.36 \(\pm\) 0.02 a & 7.45 \(\pm\) 0.03 a & 305.06 \(\pm\) 1.31 b & 1.04 \(\pm\) 0.03 b \\ C group & 3.36 \(\pm\) 0.05 a & 7.37 \(\pm\) 0.05 a & 309.87 \(\pm\) 1.46 a & 5.97 \(\pm\) 0.02 a \\ \hline \hline \end{tabular} Note: Information is presented as ’mean \(\pm\) standard deviation’ and different letters in the same column indicate significant differences (\(p\) < 0.05).  
\end{table} 
Table 1: Measurement results of physical and chemical indexes of three groups of grapes. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Grape Samples** & **Tartaric Acid (g/L)** & **Malic Acid (g/L)** & **Citric Acid (g/L)** \\ \hline A group & 11.54 \(\pm\) 0.61 a & 2.52 \(\pm\) 0.13 b & 0.55 \(\pm\) 0.05 b \\ B group & 11.11 \(\pm\) 0.69 a & 2.73 \(\pm\) 0.1 b & 0.66 \(\pm\) 0.04 a \\ C group & 10.65 \(\pm\) 0.64 a & 4.21 \(\pm\) 0.07 a & 0.66 \(\pm\) 0.03 a \\ \hline \hline \end{tabular} Note: Information is presented as ’mean \(\pm\) standard deviation’ and different letters in the same column indicate significant differences (\(p\) < 0.05).  
\end{table} 
Table 2: Determination of organic acid content in three groups of grapes. samples differed significantly (\(p<0.05\)), and the higher glycerol content in wine samples produced from group B and C grapes compared to group A grapes may be attributable to the greater levels of mold infestation. There were significant differences in color-related parameters among the three groups of wine samples, including total phenol, tartaric acid esters, and flavanol content (\(p<0.05\)). There were also statistically significant differences among the groups in the values of L\({}^{*}\), a*, and b* in the CIELAB coordinate system (\(p<0.05\); Tables 3 and 4). In the CIELAB coordinate system, l* represents the degree of brightness. Large values for l* indicate brighter colors, whereas small values of l* indicate darker colors. Coordinate parameter a* values \(>0\) are associated with the color red, whereas a* values \(<0\) are associated with green. Coordinate parameter b* values \(>0\) are associated with the color yellow, whereas b* values \(<0\) are associated with blue.