β-glucans are non-starchy polysaccharides naturally present in the cell walls of several organisms and higher cultures. Therefore, humans unintentionally consume β-glucans through their regular diet. The primary sources of food β-glucan for humans are cereals (especially oats and barley), fungi, algae, and yeast [19,20]. 

Cereal β-glucans are linear homopolymers formed by D-glucose residues bound primarily through two or three consecutive glycosidic β-(1,4) bonds separated by a single glycosidic β-(1,3) link. Longer segments with glucose residues consecutively bound by β-(1,4) glycosidic linkages and with a degree of polymerization (DP) of 5–28 are less frequent. There is no evidence that two or more adjacent glycosidic β-(1,3) bonds occur in cereal β-glucan chains [21]. The molecular characteristics of β-glucans are generally derived from the analysis of oligomers obtained from the depolymerization of polymers with a specification (1 → 3, 1 → 4) -β-D-glucan hydrolase (lichenase) releasing 3-O-β-D-cellobiose-D-glucose (trisaccharide unit, DP3) and 3-O-β-D-cellotriose-D-glucose (tetrasaccharide unit, DP4) representing 90–95% of total oligosaccharides, while longer oligosaccharides (DP ≥ 5) represent only 5–10% of the total. In brief, the molar ratio is considered as the ratio of cellotriose to cellotetraose units (DP3/DP4) following the depolymerization of the β-glucan polymer chain [18]. β-glucans from different cereal species share the same general molecular structure but differ based on the DP3/DP4 ratio, in the ratio of β-(1,3) and β-(1,4) glycosidic bonds, and in the molecular dimensions [21]. Among cereals with the highest concentrations of β-glucans are oats and barley; lower concentrations are also present in wheat, rye, and rice kernels [18].

The application of cereals β-glucans is desirable for various food products for their expected great advantages both in terms of technology and health. For technological purposes, β-glucans are mainly used as thickening agents, fat substitutes in light products, foam stabilizers, and emulsifiers. However, extraction, handling, and upstream processing treatments of β-glucans raise a number of practical challenges, particularly as a health ingredient, and their use is still limited [18]. Based on the rheological evaluation of hulled barley β-glucans, they can be incorporated into beverages and other liquid products as a thickener and as a source of dietary fiber [56]. However, the incorporation of β-glucans into foods is limited due to their high viscosity and the difficulties of industrial handling. This limitation is particularly evident when they are applied at sufficient concentrations to carry out their beneficial actions on the body [57]. In addition, cereal β-glucans could be used to promote in situ folate (i.e., Vit. B9) synthesis by certain yeasts and bacteria naturally present or added to the raw material [57,58]. The presence of β-glucans in meat emulsions meets the goal of increasing fiber levels in the diet at the same time as achieving better technological results. Unlike carrageenan and starch, which are hydrocolloids commonly used in meat products with strict legislative limits in quantities, β-glucans still require a legislative consensus on the maximum and minimum amounts that can be added to a given food matrix [25].

In solid food matrices, the addition of β-glucans has been studied mainly for cereal products (bread, rusks, pasta, biscuits, cake, etc.) In most European nations, bread is a staple diet and the main source of carbs. White bread made with wheat flour is the most popular starchy meal due to its exceptional organoleptic qualities as well as its taste. However, due to its porous structure and the large amount of gelatinized starch, it is categorized as a food with a high glycemic index (GI) [59]. Therefore, lowering the glycemic index of bread is of substantial scientific interest considering its great consumption. For this reason, the addition to bread of soluble dietary fiber, such as β-glucan concentrates from barley or oats, may be a successful strategy. In recent research, Binou et al. (2021) examined the post-prandial metabolic effects of two distinct kinds of functional breads enriched with β-glucans and resistant starch (RS) fractions, in the quantities recommended by the EFSA to have a health effect. Estimates of the test individuals’ subjective ratings of their hunger were taken together with measurements of glycemic and insulin levels, ghrelin, GLP-1, and PYY responses. Additionally, the sensory qualities of the enhanced goods were assessed. When compared to a glucose solution (GS), breads with G or RS had a smaller incremental glucose area under the curve (IAUC), and both kinds of bread had a low glycemic index (GI). The insulin, ghrelin, GLP-1, and PYY responses did not differ between the two significantly [60]. As reported by a Vitaglione et al. (2013) in a short-term study, the increase in the β-glucan fiber of snacks can modulate the appetite and energy intake of young people [61]. The research of Tessari and Lante (2017) focused on people with T2DM, evaluating the metabolic effects of a six-month replacement of ordinary white bread with a specially designed functional bread (Pane Salus^®), with a modest content of starch but high fiber, respectively, 7 g/100 g, with a β-glucan/starch ratio of 7.6:100, g/g. The diabetic participants eating the functional bread showed significantly lower levels of fasting, postprandial, and average blood glucose concentrations, as well as a lower glycated hemoglobin (HbA1c) value than the control T2DM subjects [62]. Last but not least, the degree of the liking of the bread was satisfactory. In research by Liu et al. (2020), the technological properties of functional bread doughs formulated with 80% Hulled Barley Whole Grain Flour (HLB WGF) of waxy or normal lines and only 20% common wheat flour (WF) were described. Bread made with WF alone was considered as the control. The amount of water absorbed by each type of flour was detected using the Brabender farinograph. The WGF HLB presented a much higher water absorption rate than normal WF. The water absorption rate by waxy lines was significantly higher than that by normal lines. The development time, stability time, and the FQN (Farinograph Quality Number) of the mixtures obtained with HLB WGF were significantly lower than those obtained with simple WF, while their degree of softening was higher. The strength of the HLB WGF is lower than WF, which justifies its higher softening. In addition to a greater water absorption, the mixtures enriched with HLB WGF were more viscous (especially waxy lines), gelatinized more easily with better adhesive properties, and demonstrated a greater resistance to starch retrogradation than normal WF. Visually, the bread made with WF had a significantly bigger volume than the bread made with HLB WGF. Moreover, because waxy varieties of bread contain more β-glucans than normal ones, they have a lower specific volume. The breads enriched with HLB WGF did not significantly vary from regular breads made with WF in terms of the crust color. Ultimately the higher content of β-glucan and total dietary fiber could have a positive effect on the nutritional value of the resulting breads; however, they are also accompanied by a possible negative effect on the sensory quality and work performance of the product. Although due to their hydrocolloid nature, β-glucans determine a greater yield of the dough, they also cause a deterioration in the structural properties of the bakeries, including an increase in hardness, gumminess, and chewability, as well as a decrease in cohesion and elasticity. In any case, even if bread made with HLB WGF shows different sensory properties than bread made with WF alone, overall, the latter are acceptable to consumers. Therefore, these preparations could be substituted in a bakery to produce functional breads [63]. As reported by Messia et al. (2020) the enriched flour obtained by waxy barley could be used to produce functional foods such as pasta, bread, biscuits that follow the legal requirements of the FDA and EU Regulation [64].