## 3 Results and Discussion
### Effect of Different Sterilization Methods on Lipid Metabolites in Red Raspberry Juice  
To clarify the relationship between the C6 aldehydes loss induced by sterilization treatments and the fatty acid metabolic pathway, untargeted metabolomics was employed to analyze the lipid profiles of raspberry juices treated with different sterilization methods, identifying intermediates with significant changes in abundance. A total of 59 lipid metabolites were detected across three red raspberry juice samples, and variations within and between sample groups were examined using PLS-DA analysis (Figure 5a). Remarkably, the first two principal components (PC1 and PC2) explained 98.8% of the overall variance, confirming the efficacy of the PLS-DA model in distinguishing the lipid profiles of the various juices. PC1, which carried significant weight, showed that the Euclidean distance between the HHP-treated juice and the fresh juice was smaller, with partially overlapping confidence ellipses, indicating closer lipid profiles between them. Additionally, cluster analysis was conducted based on the lipid metabolites identified in three red raspberry juice samples, with the results displayed in Figure 5b. The dendrogram at the top showed distinct clustering for juices treated by three different sterilization methods, where the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Chemical Name**}} & \multicolumn{1}{c}{**Structure**} & \multirow{2}{*}{**Alternative Name**} & \multirow{2}{*}{**Saturability**} & \multirow{2}{*}{**Fresh**} & \multirow{2}{*}{**HHP**} & \multirow{2}{*}{**HTST**} \\  & **Simple** & & & & & & \\  & **Formula** & & & & & & \\ \hline Dodecanoic acid & C12:0 & Lauric acid & Saturation & 2.85 \(\pm\) 0.07 b & 1.53 \(\pm\) 0.04 a & 2.69 \(\pm\) 0.05 b \\ Tetradeconic acid & C14:0 & Myristic acid & Saturation & 2.61 \(\pm\) 0.19 c & 2.38 \(\pm\) 0.09 a & 3.46 \(\pm\) 0.03 b \\ Hexadecanoic acid & C16:0 & Palmitic acid & Saturation & 68.13 \(\pm\) 0.77 b & 68.01 \(\pm\) 0.64 b & 69.78 \(\pm\) 0.52 a \\ (Z)-9-hexadecenoic acid & C16:1 & Palmitic acid & Monomusaturated & 2.45 \(\pm\) 0.04 b & 2.62 \(\pm\) 0.28 b & 2.19 \(\pm\) 0.01 a \\ Heptadecanoic acid & C17:0 & Perlitic acid & Saturation & 2.03 \(\pm\) 0.01 b & 2.41 \(\pm\) 0.01 b & 2.30 \(\pm\) 0.07 a \\ Octadecanoic acid & C18:0 & Vaccenic acid & Saturation & 12.30 \(\pm\) 0.52 b & 12.50 \(\pm\) 0.12 b & 15.70 \(\pm\) 0.16 a \\ (Z)-9-octadecenoic acid & C18:1n9c & Oleic acid & Monounsaturated & 42.79 \(\pm\) 1.14 c & 29.01 \(\pm\) 0.84 a & 31.97 \(\pm\) 0.88 b \\ (Z, Z)-9, & & & & & & \\
12-octadecanionic acid & C18:2n6c & Linoleic acid & Polyunsaturated & 58.12 \(\pm\) 0.76 b & 54.76 \(\pm\) 0.24 a & 54.73 \(\pm\) 1.31 a \\ Eicosanic acid & C20:0 & Arachidic acid & Saturation & 4.58 b \(\pm\) 0.05 c & 4.17 \(\pm\) 0.02 b & 5.02 \(\pm\) 0.01 a \\ (Z, Z, Z)-9, 12, & & & & & & \\
15-octadecatrienoic acid & C18:3n3 & Linolenic acid & Polyunsaturated & 59.95 \(\pm\) 0.65 b & 51.79 \(\pm\) 0.76 a & 52.12 \(\pm\) 4.03 a \\ Docosanoic acid & C22:0 & Behenic acid & Saturation & 3.81 \(\pm\) 0.04 c & 2.26 \(\pm\) 0.04 b & 4.58 \(\pm\) 0.09 a \\ Tetracosanoic acid & C24:0 & Taric acid & Saturation & 2.99 \(\pm\) 0.03 c & 2.73 \(\pm\) 0.03 b & 2.51 \(\pm\) 0.07 a \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Fatty acid contents (mg/kg) of red raspberry juices after different sterilization treatments. Values with different lowercase letters in the same row denote a significant difference (\(p<0.05\)). Figure 4: Cluster analysis based on the fatty acid composition of red raspberry juice in red raspberry juices after different sterilization treatments. HHP-treated juice exhibited a higher similarity in lipid profiles to the fresh juice. This observation aligns with the PLS-DA findings, suggesting that HHP treatment better preserves the flavor of red raspberry juice compared to HTST treatment.