## 2 Results and Discussion  
### Chemical Compositions and Color Properties  
Six pre-fermentative treatments were applied before alcoholic fermentation, as shown in Table 1. The chemical indicators and the color attributes of strawberry wines fermented by different pre-treatment methods were presented in Table 2. These strawberry wines exhibited similar levels of alcohol content (12.17-12.50%) as a result of the initial sugar content adjustment to the same level (24%) before fermentation. However, the alcohol content of PJ-fermented strawberry wine was the highest (\(p<0.05\)), which may be because the sugar and other nutrients in strawberry were extracted more effectively, thus being more accessible after pectinase treatment. Except for PJ strawberry wine, other wines all belonged to the dry type, based on total sugar contents below 4 g/L. The contents of sugar-free extract in strawberry wines fermented and kept on pulp (NM, PM) were higher than those of wines fermented from juice, suggesting an enhancement of extraction of soluble substances from strawberry pulp. Compared to no pretreatment (CJ), maceration was favored to increase the content of the sugar-free extract. More soluble solids, organic acids, polysaccharides, and phenolic substances in strawberries could be soaked out through maceration. Typically, commercial pectinase preparation includes pectinesterase, polygalactur-onase, and pectinylase. The hydrolysis of methyl ester groups in pectin by pectinesterase led to a notable increase (\(p\) < 0.05) of methanol content in the PJ and PM final wines by 1.52-15.41 times compared to those without pectinase, which was confirmed by the research of [PERSON] et al. (2017). However, these amounts (136.72 mg/L and 134.08 mg/L) did not exceed the limit set by the International Office of Vine and Wine (OIV) at \(<\)400 mg/L for red wines and \(<\)250 mg/L for white or rose wine (International Organisation of Vine and Wine, 2015). The CJ wine sample made from juice without maceration showed the lowest methanol content, and the NJ, 50J, and NM samples followed in turn. These sources of methanol were mainly due to the activation of endogenous pectinesterase, which occurs naturally in fruits and is responsible for the release of methanol in fruit juices and wines without the addition of pectinase ([PERSON] et al., 2018). The organic acid profile is highly associated with the acidity of fruit wines and is an influential factor in its flavor, which can be influenced by the fruit, yeast strain, and fermentation conditions. Five organic acids were determined in strawberry wines, including citric, malic, succininic, lactic, and acetic acid. As shown in Table 2, citric acid was the primary organic acid in strawberry wines, accounting for 59.72-71.52% of the total organic acids. Some reports have indicated that citric acid is the predominant organic acid, which is a significant fraction of the total organic acids. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Number**} & **Name and Abbreviation of** & **Fermentation Raw** & **Maceration** & **Maceration** & **Maceration** \\  & **Fermentation Method** & **Material** & **Time/h** & **Temperature\({}^{\circ}\)C** & **Pectinase** \\ \hline A & control vinfication of juice pressed & juice & / & / & / \\  & from must without pretreatment (CJ) & juice & 3 & 25 & / \\ B & vinfication of juice pressed from must & juice & 3 & 50 & / \\ C & vinfication of juice pressed from must & juice & 3 & 50 & / \\ D & vinfication of juice pressed from must & juice & 3 & 50 & added \\  & macerated at 50 \({}^{\circ}\)C with pectinase (PJ) & juice & 3 & 25 & / \\ E & vinfication of must macerated at & must & 3 & 25 & / \\  & normal temperature (NM) & must & 3 & 50 & added \\ F & vinfication of must macerated at 50 \({}^{\circ}\)C & & & & \\  & with pectinase (PM) & must & 3 & 50 & added \\ \hline \multicolumn{6}{c}{Notes: \({}^{\circ}/^{\circ}\) indicates that the process was not performed.} \\ \end{tabular}
\end{table} 
Table 1: Methods of pre-fermentation treatment.