## 3 Results and Discussion
### Composition Analysis
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Distillery** & **Protein** & **Water/Ethanol** & **Extractives** & **Cellulose** & **Hemicellulose** & **Lignin** \\ \hline D1 & 17.93 \(\pm\) 1.06 \({}^{\text{c}}\) & 24.77 \(\pm\) 0.61 \({}^{\text{bc}}\) & 20.2 \(\pm\) 0.20 \({}^{\text{cd}}\) & 17.07 \(\pm\) 3.03 \({}^{\text{ab}}\) & 14.04 \(\pm\) 0.15 \({}^{\text{a}}\) \\ D2 & 18.28 \(\pm\) 0.67 \({}^{\text{bc}}\) & 31.14 \(\pm\) 2.98 \({}^{\text{a}}\) & 16.2 \(\pm\) 1.93 \({}^{\text{e}}\  
The most common drying methods include oven drying, infrared drying, and freeze drying [39]. Drying has been found to influence the chemical composition of DSG by making dried samples more nutrient-dense than fresh DSG. For example, the drying of Indian almonds was reported to improve protein availability, attributed to the ability of drying to make foods more nutrient-dense [39]. Other preservation methods include freezing, ensiling, and the use of various additives and preservative chemicals such as lime, sodium formate, calcium propionate, formic acid, propionate acid, and acetic acid [40]. Extractives are non-structural biomass components that are soluble in water and organic solvents. Water-soluble materials may include inorganic compounds, non-structural sugars, and nitrogenous materials. Water- and ethanol-soluble materials also include chlorophyll, lipids, waves, and other minor components. In this study, the water- and ethanol-soluble extractive content ranged from 17.33% to 31.77%. Spent grain samples with a higher percentage of malted barley showed higher extractive content (24.77-31.77%), while samples with a lower percentage of malted barley exhibited lower extractive content. Similarly, high extractive values (34.8%) were reported by [PERSON] et al. [41] for corn-based distillers' grains with solubles obtained from ethanol plants. In their study, [PERSON] et al. [41] also noted that DSG contains more water-soluble extractives than organic solvent-soluble extractives, whereas [PERSON] et al. [42] reported 24.1% water- and ethanol-soluble extractives, with a higher proportion of ethanol-soluble extractives. The protein content of DSG ranges from 12.38% to 26.32%, with an average protein content of 20.29% across the nine distilleries. The protein content of six samples (D1, D2, D4, D5, D7, and D8) was significantly different from each other, while three samples (D3, D6, and D9) showed no significant differences. The results indicate that a substantial variation (67%) exists in the protein content of DSG among the distilleries, regardless of similarities in the starting grains. A similar variation in protein content was reported by [PERSON] et al. [43] for brewer's spent grain. The highest protein content (26.32%) was obtained from DSG composed of 40% malted barley, 55% unmalted barley, 1.75% rye, and 3.25% oat (D9). The lowest protein content (12.38%) was observed in DSG from Distillery 8, which used 100% malted barley. The protein content values obtained in this study align with those reported by [PERSON] et al. [44], who found values of 24.2%, 21.8%, and 26.4% for oven-dried, freeze-dried, and frozen brewer's spent grain (BSG) samples, respectively. Similarly, [PERSON] and [PERSON] [45] reported a protein content of 18.14 \(\pm\) 0.25% for BSG obtained from a single brewery in Brazil. Previous studies have found that DSG contains approximately 15% to 25% protein, making it a valuable source of animal feed [46]. The proteins in DSG are similar to those found in the original barley grain, including globulins, albumins, glutelins, and hordeins. However, the protein concentration in fresh distillers' grain is often higher than that of the original barley (9.65%) and barley malt (8.52%) because most of the starch is removed during the mashing stage, leaving a spent grain with a higher protein concentration and lower starch content [47]. [PERSON] et al. [47] reported that protein accounts for approximately 19-30% of brewer's spent grain, whereas [PERSON] et al.