## 2 Results and Discussion
### Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA)
#### 2.5.3 Variable Importance in Projection (VIP) Analysis  
The VIP scores from the OPLS-DA model provide insight into the importance of each variable in the model with respect to the projection used in the discriminant analysis. VIP scores greater than 1 suggest that a variable is important for the model, and scores greater  
Figure 4: Principal Component Analysis (PCA) of microencapsulations produced from different wall materials compared to a sample made from fresh tea. The PCA plot shows the distribution and clustering of microencapsulated samples (gelatin, acacia gum, carboxymethylcellulose (CMC), maltodextrin) and fresh tea based on their aroma profiles. than 1 are listed in Table 1 and Figure S5 in the Supplementary Materials, indicating that they were highly influential variables. The impacts of different microcapsule wall materials on the retention and release of aroma compounds are closely related to the structural characteristics and types of these compounds. Esters, such as acetic acid phenylmethyl ester and methyl salicate, are characterized by their -COOR functional groups, making them relatively non-polar and volatile. These esters are likely to interact more effectively with wall materials that have hydrophobic characteristics, such as gelatin, which possesses both hydrophilic and hydrophobic regions. This dual nature of gelatin allows it to form stable hydrogen bonds or hydrophobic interactions, leading to better retention of these volatile esters. Siloxanes, including compounds like cyclotetrasiloxane and cycloheptasiloxane, are highly hydrophobic due to their silicon-oxygen backbone and attached methyl groups. Their encapsulation is more efficient in wall materials that are less polar, as hydrophobic interactions play a crucial role in their retention. Conversely, predominantly hydrophilic wall materials may lead to a greater loss of these volatile siloxanes during processing. Alcohols, such as linalool and 3-hexen-1-ol, contain hydroxyl groups that make them somewhat polar, allowing them to form hydrogen bonds with wall materials like gelatin. This can enhance their retention, although their inherent volatility still poses a challenge, particularly during drying. Aromatic compounds, including indole and methyl anthranilate, contain benzene rings and other functional groups that contribute to their distinct odors. These compounds can interact with both hydrophilic and hydrophobic wall materials, and gelatin, with its ability to form complex interactions through hydrogen bonding and Van der Waals forces, can effectively retain these aromatic compounds. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Var ID** & **Aroma Compound** & **VIP Value** \\ \hline V10 & Acetic acid, phenylmethyl ester & 2.93 \\ \hline V3 & Cyclotetrasiloxane, octamethyl- & 2.37 \\ \hline V27 & Undecanoic acid, ethyl ester & 2.18 \\ \hline V68 & Butylated hydroxytoluene & 2.08 \\ \hline V25 & Cycloheptasiloxane, tetradecamethyl- & 1.89 \\ \hline V58 & Cyclotrisiloxane, hexamethyl- & 1.81 \\ \hline V24 & 2(3H)-Furanone, dihydro-5-propyl- & 1.78 \\ \hline V9 & Cyclopentasiloxane, decamethyl- & 1.61 \\ \hline V15 & Cyclohexasiloxane, dodecamethyl- & 1.60 \\ \hline V8 & Linalool & 1.58 \\ \hline V51 & Oxime-, methoxy-phenyl-\({}_{-}\) & 1.56 \\ \hline V26 & 2H-Pyran, 2-[(5-cyclopropylidenepently)]oxy]tetrahydro- & 1.56 \\ \hline V14 & Indole & 1.49 \\ \hline V32 & 3-Hexen-1-ol, benzoate, (Z)- & 1.47 \\ \hline V11 & Methyl salicate & 1.42 \\ \hline V7 & Benzoic acid, methyl ester & 1.40 \\ \hline V33 & Dodecanoic acid, ethyl ester & 1.38 \\ \hline V16 & Methyl anthranilate & 1.35 \\ \hline V82 & 2(3H)-Furanone, 5-hexyldihydro- & 1.25 \\ \hline V65 & 2-Heptanone, 5-methyl- & 1.22 \\ \hline V12 & Decanal & 1.18 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The aroma compounds with VIP values higher than 1. Ketones, represented by compounds like 2-heptanone, have carbonyl groups that are moderately polar, allowing for potential hydrogen bonding with wall materials.