## 3 Pretreatment and Processing Technologies  
Efficient processing and extraction of DGP and SSGP necessitate appropriate pretreatment methods to disrupt the complex plant cell wall matrix and enhance the accessibility and recovery of target molecules such as bioactive polyphenols and dietary fibers. These pretreatments can be broadly categorized into mechanical, chemical, and enzymatic approaches, often used in combination to maximize yields and product quality.  
Mechanical pretreatments are fundamental first steps, primarily involving drying, milling, and size reduction. Drying is crucial for reducing moisture content, preventing microbial spoilage, concentrating compounds, and preparing the material for subsequent processing. Methods such as convective air drying, freeze-drying, and microwave-assisted drying are employed, with the choice influencing energy consumption and the preservation of thermolabile compounds, including certain polyphenols [40]. Following drying, milling or grinding reduces particle size, significantly increasing the surface area available for solvent penetration and interaction. This enhanced surface area is directly correlated with improved extraction efficiency of both polyphenols and the subsequent accessibility of dietary fiber components [41].  
Chemical pretreatments predominantly involve the use of solvents for extraction, but they can also include treatments to modify fiber structure. For the extraction of phenolic compounds, solvents such as water, ethanol, methanol, acetone, and their aqueous mixtures have been investigated. Ethanol-water mixtures are particularly favored due to their Generally Recognized as Safe (GRAS) status and their ability to efficiently extract a broad range of substances. The choice of solvent, temperature, and extraction time is a critical parameter influencing yield and selectivity [42]. Emerging green solvents, such as deep eutectic solvents (DES), are also gaining attention for their efficacy and environmental benefits. For dietary fiber modification or isolation, mild acid or alkaline treatments can be used to hydrolyze hemicellulose or delignify the material, making cellulose more accessible. However, this process must be carefully controlled to preserve other valuable components.  
Enzymatic pretreatments provide a more targeted and gentle approach to deconstructing the plant cell wall, thereby releasing entrapped bioactive compounds and modifying the  
\begin{table}
\begin{tabular}{l l l} \hline
**Component** & **Amount** & **References** \\ \hline Moisture content & 3–7 & [36; 37] \\ Lignin & 27–56 & [26; 37; 39] \\ Proteins & 2.8–3.0 & [36] \\ Phenolic compounds & 0.5–0.6 & [38] \\ Minerals & 1.5–10 & [36; 37] \\ \hline \end{tabular}
\end{table}
Table 2: Representative composition of SSGP (g/100 g, as-is basis).  
characteristics of dietary fiber. Enzymes such as cellulases, hemicellulases, pectinases, and tannases can be used individually or in combinations. These enzymes catalyze the hydrolysis of specific polysaccharides, including cellulose, hemicellulose, and pectin, which form the structural backbone of the cell wall. This process improves the release of polyphenols and increases the soluble dietary fiber fraction. Enzyme-assisted extraction (EAE) often yields higher polyphenol concentrations under gentler conditions, such as lower temperatures and less organic solvent, compared to conventional methods, thereby preserving their bioactivity [43]. Furthermore, enzymatic treatment can enhance the functional properties of dietary fibers, such as their water-holding capacity and fermentability.