# Insight on Extraction and Preservation of Biological Activity of Cereal \(\beta\)-D-Glucans
## 4 Methods of Extraction and Purification of Cereal \(\beta\)-D-Glucans
### Dry Technologies
The purity of \(\beta\)-D-glucans extract in alkali can be increased by fractional precipitation and digestion with xylanase [42]. Fractional precipitation can be performed at increasing concentrations of (NH4)2 SO4 in water, because the solubility of \(\beta\)-D-glucans and AXs in this medium is different. \(\beta\)-D-glucans can be precipitated to a much lower (NH4)2 SO4 saturation level (20-55%) than AXs (55-95%) [43]. However, the precipitation techniques do not always separate the polysaccharides completely. Another approach is to use more \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Sources** & **Arabinoxylans** & **Glucans (\(\beta\)-D-Glucans)** \\ \hline \multirow{8}{*}{Bran} & Barley & 19.0–21.4 & 6.15–7.58 \\ \cline{2-4}  & Oat & 3.0 & 5.4–8.5 \\ \cline{2-4}  & Rice & 4.8–5.1 & 0.04–0.21 \\ \cline{2-4}  & Wheat & 18.0–24.0 & 2.1 \\ \cline{2-4}  & Rye & 12.0–18.0 & 2.9 \\ \cline{2-4}  & Corn & 27.2–29.9 & 0.1 \\ \hline \multirow{8}{*}{Husk} & Barley & 19.0–20.0 & 37–40 \\ \cline{2-4}  & Oat & 3.5 & 37.10 \\ \cline{2-4}  & Rice & 8.4–9.2 & 34.2 \\ \cline{2-4}  & Wheat & NR & 38.2 \\ \cline{2-4}  & Soybean & 13.1 & NR \\ \hline \multirow{8}{*}{Straw} & Barley & 11.0–14.0 & 33.6 \\ \cline{2-4}  & Oat & NR & 32.1 \\ \cline{1-1} \cline{2-4}  & Rice & 11.0–18.3 & 34.1 \\ \cline{1-1} \cline{2-4}  & Wheat & NR & 30.4 \\ \cline{1-1} \cline{2-4}  & Rye & NR & 33.12 \\ \cline{1-1} \cline{2-4}  & Corn & 27.0–30.0 & 40.9 \\ \hline \multicolumn{4}{c}{Corn cob} & 12.8 & 41.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Amounts (%, dry weight) of arabinylans and glucans in cereal residues and byproducts. Table adapted from [39]. selective extraction solvents, such as Ba(OH)\({}_{2}\) solutions that interact preferably with pentose sugars and then extracting AX and avoiding coextraction with \(\beta\)-D-glucans that remain insoluble in solution [41; 42]. The key disadvantage of these wet separation technique is their high cost of production [9]. Extraction with Water  
The \(\beta\)-D-glucans obtained by simple aqueous extraction, although leading to a high-purity \(\beta\)-D-glucans extract, showed low viscosity in the solution when reconstituted in water. This is mainly attributed to the depolymerization of \(\beta\)-D-glucans by endogenous enzymes (\(\beta\)-D-glucanas) naturally present in flows. The loss of viscosity due to depolymerization following enzymatic hydrolysis is not desirable, as viscosity is a fundamental parameter for its health effects. Another disadvantage of this type of extraction is the high cost of production, mainly due to the large volume of water required in the initial phase to hydrate and solubilize the \(\beta\)-D-glucans (the \(\beta\)-D-glucan ratio: water should be at least 1:200, \(w/w\)) and the consequent high volume of absolute alcohol to dehydrate and precipitate the \(\beta\)-D-glucans from the aqueous solution in the terminal phase (\(\sim\)50% \(v/v\)) [33]. Among the best conventional methods used for the wet extraction of cereal \(\beta\)-D-glucans, the extraction with alkali is the one that allows the greatest solubilization and consequent extraction of cereal \(\beta\)-D-glucans. In addition to the high yield, it also has good purity of extract. The process involves four main steps:  
1. Mixing: The ground wheat/flour/oat bran or barley is mixed in an alkaline aqueous solution (pH-10), generally basified using Na\({}_{2}\)CO\({}_{3}\) or NaOH. The \(\beta\)-D-glucans and proteins are then solubilized. 2. Centrifugation of the compound: The insoluble solid particles, starch, and insoluble fiber are separated from the liquid phase containing the solubilized \(\beta\)-D-glucans and proteins. 3. Precipitation of proteins once their isoelectric point (pH-4-5) is reached by adding acid. The proteins are then removed from the liquid phase by centrifugation. 4. Recovery of \(\beta\)-D-glucan concentrate from the liquid phase by alcohol precipitation and centrifugation, followed by drying [44].