Optimization of the β-glucan extraction conditions from different waxy barley cultivars

Structural and rheological characterization of water-soluble and alkaline-soluble fibers from hulless barley

BACKGROUND

Highland hulless barley has garnered attention as a promising economic product and a potential healthy food ingredient. The present study aimed to comprehensively investigate the molecular structure of extractable fibers obtained from a specific highland hulless barley. Water-soluble fiber (WSF) and alkaline-soluble fiber (ASF) were extracted using enzymatic digestion and an alkaline method, respectively. The purified fibers underwent a thorough investigation for their structural characterization.

RESULTS

The monosaccharide composition revealed that WSF primarily consisted of glucose (91.7%), whereas ASF was composed of arabinose (54.5%) and xylose (45.5%), indicating the presence of an arabinoxylan molecule with an A/X ratio of 1.2. The refined structural information was further confirmed through methylation, 1 H NMR and Fourier-transform infrared spectroscopy analyses. WSF fiber exclusively exhibited α-anomeric patterns, suggesting it was an α-glucan. It has a low molecular weight of 5 kDa, as determined by gel permeation chromatography. Conversely, ASF was identified as a heavily branched arabinoxylan with 41.55% of '→2,3,4)-Xylp-(1→' linkages. ASF and WSF exhibited notable differences in their morphology, water absorption capabilities and rheological properties.

CONCLUSION

Based on these findings, molecular models of WSF and ASF were proposed. The deep characterization of these fiber structures provides valuable insights into their physicochemical and functional properties, thereby unlocking their potential applications in the food industry. © 2023 Society of Chemical Industry.

Cereal β-d-Glucans in Food Processing Applications and Nanotechnology Research

Cereal (1,3)(1,4)-β-d-glucans, known as β-d-glucans, are cell wall polysaccharides observed in selected plants of grasses, and oats and barley are their good natural sources. Thanks to their physicochemical properties β-d-glucans have therapeutic and nutritional potential and a specific place for their functional characteristics in diverse food formulations. They can function as thickeners, stabilizers, emulsifiers, and textural and gelation agents in beverages, bakery, meat, and extruded products. The objective of this review is to describe the primary procedures for the production of β-d-glucans from cereal grains, to define the processing factors influencing their properties, and to summarize their current use in the production of novel cereal-based foods. Additionally, the study delves into the utilization of β-d-glucans in the rapidly evolving field of nanotechnology, exploring potential applications within this technological realm.

Beta-Glucans of Cereals: Functional and Technological Properties

β-glucans are a polymeric dietary fiber characterized by β-(1,3) and β-(1,4) glycosidic bonds between glucose monomers. They are often used as thickeners, stabilizers, and fat substitutes in foods. The functional and technological quality of β-glucans is attributed to their origin/source, molecular weight, and structural properties. In particular, physical treatments such as drying, cooking, freezing, and refrigeration influence their molecular, morphological, and rheological characteristics. In addition to their useful technical qualities, β-glucans are recognized for their numerous beneficial impacts on human health. For this reason, the European Food Safety Authority (EFSA) has provided a positive opinion on health claims such as cholesterol lowering and hypoglycemic properties relating to oats and barley β-glucans. This paper provides insight into the properties of β-glucans and different treatments affecting their characteristics and then reviews the latest research on β-glucans as a functional ingredient for people with type 2 diabetes mellitus (T2DM).

Comparison of distribution and physicochemical properties of β-glucan extracted from different fractions of highland barley grains

Highland barley grains were roller-milled to produce five different fractions (B-1, B-2, B-3, B-4, and B-5). The distribution and physicochemical properties of β-glucans from five roller-milled fractions were investigated. The B-4 fraction contained the highest concentration of β-glucan (4.40%), and the outermost bran (B-1) had the lowest β-glucan content (1.01%). Besides, β-glucans from inner core B-5 (BG-5) had higher M_w (6.482 × 10⁵ g/mol), whereas β-glucans from outer bran B-1 (BG-1) showed lower M_w (5.859 × 10⁴ g/mol) than those from other fractions. Accordingly, the viscosity of BG-5 was highest (0.038-0.365 Pa·s), and the water solubility index of BG-1 was highest (50.43-90.71%). BG-5 showed stronger foam stability and emulsifying properties but weaker foaming capability, while BG-1 exhibited stronger foaming capability. The foaming capability and emulsifying properties of β-glucan samples were better under the neutral condition (pH = 7). The foam capabilities of all β-glucan samples displayed higher values at 65 °C, and emulsifying properties exhibited higher values at 45 °C. This study is expected to promote the application of highland barley β-glucans in food industry.

Influence of Oat β-Glucan on the Survival and Proteolytic Activity of Lactobacillus rhamnosus GG in Milk Fermentation: Optimization by Response Surface

β-glucans come from cereals that have been located within compounds with prebiotic activity. They have presented several bioactivities that have determined their high functional value. The aim of this study was to identify the influence of oat β-glucan on the survival and proteolytic activity of Lactobacillus rhamnosus GG in a milk fermentation through an experimental design to optimize the process. For β-glucan extraction after dry milling of oats, two methods were applied: with and without enzymatic inactivation of the semolina. The highest extraction yield (45.25 g/L) was obtained with enzymatic inactivation. For the optimization of survival and proteolytic activity, a central design composed of axial points with two factors on three levels was used. Control factors were β-glucan and inoculum concentrations. According to response surface, the best survival growth rate of probiotic was observed with 4.38% of inoculum and 22.46 g/L of β-glucan, and the highest production of free amino groups was observed with 4.18% of inoculum and 22.71 g/L of β-glucan. Thus, β-glucan promotes the proteolytic activity of Lb. rhamnosus GG in milk fermentation.

Comparison of physicochemical properties of β-glucans extracted from hull-less barley bran by different methods

In this study, four extraction methods, including ultrasonic extraction (UE), hot water extraction (HWE), microwave extraction (ME), and microwave-assisted ultrasonic extraction (MUE) were utilized to extract β-glucan from hull-less barley bran. Extraction yields and physicochemical properties of β-glucans extracted by different methods were investigated. The MUE displayed a highest extraction yield (2.16%) within shorter extraction time. Besides, β-glucans extracted by MUE (MUE-G) had higher number-average molecular weight (M_n) (3.415 × 10⁵), whereas β-glucans extracted by UE (UE-G) showed lower M_n (2.257 × 10⁵) as compared to other methods. Accordingly, apparent viscosity of MUE-G was highest, while water solubility index of UE-G was highest (34.18-88.81%) at tested temperature ranges (25-95 °C). The MUE-G shower stronger foam stability and emulsifying properties and weaker foaming capability, while UE-G exhibited stronger foaming capability. The foaming capability and emulsifying properties of β-glucan products were better in neutral solutions (pH = 7) than in the acidic (pH = 4) and alkaline (pH = 9).

The detection, purity and structural properties of partially soluble mushroom and cereal β-D-glucans: A solid-state NMR study

β-D-glucans are proposed to have many health benefits. It is therefore important to have methods which can distinguish these from other carbohydrates present in natural products, as well as giving glucan content and structural information. Correlations between features in the CP/MAS spectra of β-D-glucans and enzyme assay determined β-D-glucan content were generally found to be poor. The β-D-glucan in dry and hydrated forms of the mushroom Ganoderma lucidum was investigated in detail by spectral peak fitting to the anomeric carbon C1 region in CP/MAS NMR spectra. Hydrated samples gave spectra with enhanced resolution and suggested that a clear distinction between β-D-glucans and other carbohydrates could be possible in the anomeric carbon C1 region. Chemical shift values for a range of carbohydrate polymers, which can be found alongside β-D-glucans, as well as the values for various linkages are given. Contamination by other carbohydrates and buffer salts is discussed.

Hydrolysis of beta-glucan in oat flour during subcritical-water extraction

Oat (Avena sativa L.) β-glucan is bound tightly to other components of the endosperm cell wall, which means that β-glucan extraction processes are complex and involve many different stages. Subcritical-water extraction (SWE) has emerged as a promising method for extracting β-glucan under high temperature and pressure conditions. This study investigated the efficiency of the SWE of β-glucan from oat flour. The yield of β-glucan was optimized under the following conditions: extraction temperature of 200 °C, solvent pH of 4.0, extraction time of 10 min, and particle size of 425-850 μm. The extraction yield under the optimal condition was 6.98 ± 1.17 g/100 g oat flour, which was more than twofold higher than when using hot-water extraction at 60 °C for 3 h. β-glucan degradation to 5-hydroxymethyl-2-furaldehyde was increased under high-temperature conditions. SWE is a feasible alternative for extracting β-glucan in a single-step process, and could be developed into an effective industrial process.

Ozonolysis of straw from Secale cereale L. for anaerobic digestion

The effect of different ozonation conditions on straw from Secale cereale (rye straw) pretreatment has been investigated. Using the Taguchi method, this study analyzed the optimum conditions for pretreatment of rye straw by ozonation. After 60min of rye straw ozonation the concentration of reducing sugars (RS) and volatile fatty acid (VFA), chemical oxygen demand (COD) were 7.4, 32.3 and 11.7 times higher, respectively compared to samples raw rye straw. The most effective rye straw ozonation occurred while using the highest amount of the rye straw (15g) treated with lower ozone dose (100gO₃/m³) in the longest period of time (60min). For this variant of experiment the increment of methane production was 291.71dm³CH₄/kgVS. Moreover, co-digestion of sewage sludge with addition of 20% ozonated rye straw allowed to obtain 269.1dm³CH₄/kgVS. The positive effect of ozone on changes in the rye straw structure has been confirmed by SEM and FTIR analysis.

Dissolution of (1-3),(1-4)-β-Glucans in Pressurized Hot Water: Quantitative Assessment of the Degradation and the Effective Extraction

The purpose of this work was to study the behavior of (1-3)(1-4)-β-D-glucan in pressurized hot water. For this purpose, solid β-glucan (450 kDa) was put in water and heated at different temperatures (120, 150, and 170°C) for different times (5 to 360 minutes). At 120°C it was found that the highest soluble β-glucan concentration was measured after 60 minutes; at 150 and 170°C optimal times were 45 and 20 minutes, respectively. The maximum amount of β-glucan dissolved in each of the optimal conditions was 1.5, 2.2, and 2.0 g/L, respectively. Under those conditions an important reduction was observed in the molecular weight: at 120°C and 60 min it was 63 kDa; at 150°C and 45 min it was reduced down to 8 kDa; and at 170°C and 20 min it was only 7 kDa. Besides this reduction in the MW some hydrolysis products, such as glucose and HMF, were observed. These results revealed the convenience of using PHW to dissolve β-glucans since the operation times, compared to the conventional process (55°C, 3 h), were reduced despite the fact that the MW was significantly reduced once the β-glucan was dissolved; therefore, PHW can be used to extract β-glucans from barley under controlled conditions in order to prevent severe degradation.

A Review of Extraction and Analysis of Bioactives in Oat and Barley and Scope for Use of Novel Food Processing Technologies

Oat and barely are cereal crops mainly used as animal feed and for the purposes of malting and brewing, respectively. Some studies have indicated that consumption of oat and barley rich foods may reduce the risk of some chronic diseases such as coronary heart disease, type II diabetes and cancer. Whilst there is no absolute consensus, some of these benefits may be linked to presence of compounds such as phenolics, vitamin E and β-glucan in these cereals. A number of benefits have also been linked to the lipid component (sterols, fatty acids) and the proteins and bioactive peptides in oats and barley. Since the available evidence is pointing toward the possible health benefits of oat and barley components, a number of authors have examined techniques for recovering them from their native sources. In the present review, we summarise and examine the range of conventional techniques that have been used for the purpose of extraction and detection of these bioactives. In addition, the recent advances in use of novel food processing technologies as a substitute to conventional processes for extraction of bioactives from oats and barley, has been discussed.