# Insight on Extraction and Preservation of Biological Activity of Cereal \(\beta\)-D-Glucans
## 5 Causes of Degradation of \(\beta\)-Glucans  
Many of the functional and health properties related to \(\beta\)-D-glucans are attributed to the viscosity of \(\beta\)-D-glucans, in turn governed by their MW and concentration. Extractionand processing methods can affect the functional characteristics of \(\beta\)-D-glucans, causing their depolymerization and viscosity reduction. The main cause of \(\beta\)-D-glucans depolymerization is due to the hydrolase activity of endogenous \(\beta\)-D-glucanases when extracts are in an aqueous medium. Especially in the preparation of bakeries, the hydrolysis of \(\beta\)-D-glucans is an important problem. The mixing time, in which the flour is hydrated and processed, as well as the fermentation time, cause a substantial depolymerization of the \(\beta\)-D-glucan chain, resulting in a decrease in MW and viscosity and loss of technological and functional properties [52; 53]. It becomes imperative to understand the stability of \(\beta\)-D-glucans and the effect of various extraction and processing conditions on physicochemical characteristics, in particular viscosity and MW. Many studies have reported that various processing methods, such as application of high-pressure-assisted homogenization, ultrasonic treatment, addition of ascorbic acid, extrusion, and irradiation, result in a decrease in the MW of \(\beta\)-D-glucans [7; 9; 10]. \(\beta\)-D-glucans can also be chemically degraded by the presence of Reactive Oxygen Species (ROS), which can lead to oxidative depolymerization. Iron (Fe\({}^{2+}\)), even in small quantities, can promote the formation of hydroxyl radicals (OH-) and, consequently, the depolymerization of polysaccharides. Moreover, this degradation process can be increased by the presence of ascorbic acid [54]. High temperatures can also lead to the hydrolysis of \(\beta\)-D-glucan molecules, and there is a synergistic effect with the presence of ROS. For example, the same treatment at 85 \({}^{\circ}\)C causes a slow hydrolysis of the \(\beta\)-D-glucan molecule without affecting the glucose monomers in the absence of pro-oxidant species, while in the presence of Fe\({}^{2+}\) and hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)), large amounts of OH- are induced, causing a rapid and extensive degradation of \(\beta\)-D-glucan and, at the same time, the generation of new functional groups (lactones, carboxylic acid, aldehydes, and ketones) [55]. The presence of phytic acid, on the other hand, a natural molecule used by plants to accumulate phosphorus inside the seeds and fibrous parts during maturation, can protect against oxidative stress. This is because phytic acid, known as an antinutrient capable of chelating certain mineral cations such as calcium, iron, magnesium, manganese, and zinc into insoluble complexes that reduce their bioavailability, is also a powerful antioxidant, since subtracting iron from the Fenton reaction reduces oxidative stress, protecting against free radicals and delaying cellular aging processes [56]. Moreover, thermal degradation is drastic if the treatments are carried out at high temperatures for prolonged periods (120 \({}^{\circ}\)C for 30 min), and it is even more intense in unpurified extracts [57]. The extrusion firing treatment can also decrease \(\beta\)-D-glucan content, especially if humidity and temperature are high [58]. Extrusion can have an impact on both the MW of \(\beta\)-D-glucan and its extractability depending on the parameters applied. Food ingredients undergo many \"order-disorder\" transitions (starch gelatinization, protein denaturation, and formation of complexes between lipids and amylose), thus altering the physical and chemical properties of the extruded products [59]. High temperatures, high pressures, and mechanical forces applied during extrusion can break and recombine the covalent bonds between monomers, thus modifying the physical structures of macromolecules and leading to a change in their functional properties.