A global set of barley varieties shows a high diversity in starch structural properties and related gelatinisation characteristics

The gelatinisation temperature and bimodal granule size distribution of barley starch are important characteristics regarding resource efficiency and product quality in the brewing industry. In this work, the diversity in starch amylose content and granule proportions in a set of modern barley varieties (N = 23) was investigated and correlated with their starch gelatinisation behaviour. Milled barley samples had peak starch gelatinisation temperatures ranging from 60.1 to 66.5 °C. Upon separating the barley starch from the non-starch compounds, sample-dependent decreases in starch gelatinisation temperatures were observed, indicating the importance of differences in barley composition. The peak gelatinisation temperatures of milled barley and isolated barley starches were strongly correlated (r = 0.96), indicating that the behaviour of the starch population is strongly reflected in the measurements performed on milled barley. Therefore, we investigated whether amylose content or starch granule size distribution could predict the gelatinisation behaviour of the starches. Broad ranges in the small starch granule volumes (13.9-32.0 v/v%) and amylose contents (18.2-30.7 w/w%) of the barley starches were observed. For the barley samples collected in the north of the USA (N = 8), the small starch granule volumes correlated positively with the peak gelatinisation temperatures of barley starches (r = 0.90, p < 0.01). The considerable variation in starch properties described in this work highlights that, besides starch content, starch gelatinisation temperature or granule size distribution might provide brewers with useful information to optimise resource efficiency.

The occurrence and structural heterogeneity of arabinoxylan in commercial pilsner beers and their non-alcoholic counterparts

The impact of arabinoxylan (AX) on the brewing process and beer characteristics depends on its content and structure and is often overlooked in research and industry. This paper reports on the occurrence and structural heterogeneity of AX in a set of commercial pilsner beers and their non-alcoholic counterparts. Fractionation by graded ethanol precipitation allowed us to isolate AX-rich fractions from beer with a number-average degree of polymerisation of 4 to 308 and an average degree of substitution in the range of 0.43 to 0.88. Pilsner beers had a higher content of high-molecular-weight AX than their non-alcoholic counterparts. The structural heterogeneity among the various commercial beers differed. By comparing the chemical composition of the beers, differences in beer production methods and ingredient selection were deduced and used to tentatively explain the differences in AX content and structural heterogeneity.

Non-starch polysaccharides in beer and brewing: A review of their occurrence and significance

It has become apparent that beer (both alcoholic and nonalcoholic) contains appreciable amounts of non-starch polysaccharides, a broad subgroup of dietary fiber. It is worth noting that the occurrence of non-starch polysaccharides in alcoholic beer does not imply this should be consumed as a source of nutrition. But the popularity of nonalcoholic beer is growing, and the lessons learnt from non-starch polysaccharides in brewing can be largely translated to nonalcoholic beer. For context, we briefly review the origins of dietary fiber, its importance within the human diet and the significance of water-soluble dietary fiber in beverages. We review the relationship between non-starch polysaccharides and brewing, giving focus to the techniques used to quantify non-starch polysaccharides in beer, how they affect the physicochemical properties of beer and their influence on the brewing process. The content of non-starch polysaccharides in both regular and low/nonalcoholic beer ranges between 0.5 - 4.0 g/L and are predominantly composed of arabinoxylans and β-glucans. The process of malting, wort production and filtration significantly affect the soluble non-starch polysaccharide content in the final beer. Beer viscosity and turbidity are strongly associated with the content of non-starch polysaccharides.

A Robust Fermentation Process for Natural Chocolate-like Flavor Production with Mycetinis scorodonius

Submerged fermentation of green tea with the basidiomycete Mycetinis scorodonius resulted in a pleasant chocolate-like and malty aroma, which could be a promising chocolate flavor alternative to current synthetic aroma mixtures in demand of consumer preferences towards healthy natural and ‘clean label’ ingredients. To understand the sensorial molecular base on the chocolate-like aroma formation, key aroma compounds of the fermented green tea were elucidated using a direct immersion stir bar sorptive extraction combined with gas chromatography–mass spectrometry–olfactometry (DI-SBSE-GC-MS-O) followed by semi-quantification with internal standard. Fifteen key aroma compounds were determined, the most important of which were dihydroactinidiolide (odor activity value OAV 345), isovaleraldehyde (OAV 79), and coumarin (OAV 24), which were also confirmed by a recombination study. Furthermore, effects of the fermentation parameters (medium volume, light protection, agitation rate, pH, temperature, and aeration) on the aroma profile were investigated in a lab-scale bioreactor at batch fermentation. Variation of the fermentation parameters resulted in similar sensory perception of the broth, where up-scaling in volume evoked longer growth cycles and aeration significantly boosted the concentrations yet added a green note to the overall flavor impression. All findings prove the robustness of the established fermentation process with M. scorodonius for natural chocolate-like flavor production.

Potential Valorization of Hazelnut Shells through Extraction, Purification and Structural Characterization of Prebiotic Compounds: A Critical Review

Hazelnuts are one of the most widely consumed nuts, but their production creates large quantities of by-products, especially shells, that could be upcycled into much more valuable products. Recent studies have shown that hazelnut shell hemicellulose is particularly rich in compounds that are potential precursors of xylooligosaccharides and arabino-xylooligosaccharides ((A)XOS), previously defined as emerging prebiotics very beneficial for human health. The production of these compounds on an industrial scale-up could have big consequences on the functional foods market. However, to produce (A)XOS from a lignocellulosic biomass, such as hazelnut shell, is not easy. Many methods for the extraction and the purification of these prebiotics have been developed, but they all have different efficiencies and consequences, including on the chemical structure of the obtained (A)XOS. The latter, in turn, is strongly correlated to the nutritional effects they have on health, which is why the optimization of the structural characterization process is also necessary. Therefore, this review aims to summarize the progress made by research in this field, so as to contribute to the exploitation of hazelnut waste streams through a circular economy approach, increasing the value of this biomass through the production of new functional ingredients.

Assessing the impact of xylanase activity on the water distribution in wheat dough: A 1H NMR study

The molecular mobility of water and biopolymers in wheat dough and the influence of xylanases thereon was investigated with time domain proton nuclear magnetic resonance relaxometry. To reduce the complexity, model systems containing starch, gluten and/or water-unextractable arabinoxylan (WU-AX) were used. In the starch-WU-AX-water model, starch binds water fast but less strong compared to WU-AX, resulting in water withdrawal from starch during resting. In contrary, WU-AX did not affect the water distribution in a gluten-WU-AX-water system, despite the higher water retention capacity (WRC) of WU-AX compared to gluten. In a starch-gluten-WU-AX-water model and in wheat flour, water was distributed over the different constituents including WU-AX. Addition of xylanase reduced the WRC of WU-AX, resulting in a release of water. Therefore, the beneficial effect of xylanase on dough and bread quality can, in part, be attributed to the redistribution of water, initially bound by WU-AX, between the other flour constituents.

Arabinoxylan from non-malted cereals can act as mouthfeel contributor in beer

A satisfying mouthfeel is essential for the production of non-alcoholic, low-alcohol beers and light beers. This paper highlights the importance of non-starch carbohydrates as mouthfeel contributors in this context. Beers were brewed with a substitution of 20 % barley malt grits by non-malted barley, rye or oats compared to a control. For the beer brewed with rye, both a 53 % increase in arabinoxylan content and an increase in the average degree of polymerization from 29 to 50 were observed. Compared to the control beer (1.48 mm²/s), viscosity was the highest for the rye beer (1.85 mm²/s). Multivariate data analysis underlined the role of arabinoxylan content and degree of polymerization as determinants of beer viscosity. A sensory panel distinguished a low-alcohol rye beer as the one with increased fullness compared to a 100 % malt beer. These experiments suggest that rye addition can be used as a strategy to increase the beer fullness.

Non-Starch Polysaccharides in Wheat Beers and Barley Malt beers: A Comparative Study

Non-starch polysaccharides (NSPs) in beers attract extensive attention due to their health benefits. The aim of this work was to investigate and compare NSPs including arabinoxylan, arabinogalactan, β–glucans, and mannose polymers in wheat and barley malt beers as well as the influence on its quality. NSPs in wheat beers (1953–2923 mg/L) were higher than that in barley malt beers (1442–1756 mg/L). Arabinoxylan was the most abundant followed by arabinogalactan. In contrast to barley malt beers, wheat beers contained more mannose polymers (130–182 mg/L) than β-glucan (26–99 mg/L), indicating that more arabinoxylan, arabinogalactan, and mannose polymers came from wheat malt. The substitution degree of arabinoxylan in wheat beers (0.57–0.66) was lower than that in barley malt beers (0.68–0.72), while the degree of polymerization (38–83) was higher (p < 0.05) than that in barley malt beers (38–48), indicating different structures of arabinoxylan derived from barley malt and wheat malt. NSPs, especially arabinoxylan content, positively correlated (p < 0.01) with real extract and viscosity of beers. Furthermore, wheat and barley malt beers were well separated in groups by principal component analysis.

In Vitro Fermentation Patterns of Rice Bran Components by Human Gut Microbiota

Whole grain rice is a rich source of fiber, nutrients, and phytochemicals that may promote gastrointestinal health, but such beneficial components are typically removed with the bran during polishing. Soluble feruloylated arabinoxylan oligosaccharides (FAXO) and polyphenols (RBPP) isolated from rice bran are hypothesized to have positive impacts on human gut microbiota through a prebiotic function. Using an in vitro human fecal fermentation bioassay, FAXO and RBPP treatments were assessed for short-chain fatty acids (SCFA) production patterns and by evaluating their impacts on the phylogentic composition of human gut microbiota by 16S rRNA gene sequencing. Fresh fecal samples collected from healthy adults (n = 10, 5 males, 5 females) were diluted with anaerobic medium. Each sample received five treatments: CTRL (no substrates), FOS (fructooligosaccharides), FAXO, RBPP, and MIX (FAXO with RBPP). Samples were incubated at 37 °C and an aliquot was withdrawn at 0, 4, 8, 12, and 24 h Results showed that SCFA production was significantly increased with FAXO and was comparable to fermentation with FOS, a well-established prebiotic. RBPP did not increase SCFA productions, and no significant differences in total SCFA production were observed between FAXO and MIX, indicating that RBPP does not modify FAXO fermentation. Changes in microbiota population were found in FAXO treatment, especially in Bacteroides, Prevotella, and Dorea populations, indicating that FAXO might modulate microbiota profiles. RBPP and MIX increased Faecalibacterium, specifically F. prausnitzii. Combined FAXO and RBPP fermentation increased abundance of butyrogenic bacteria, Coprococcus and Roseburia, suggesting some interactive activity. Results from this study support the potential for FAXO and RBPP from rice bran to promote colon health through a prebiotic function.

Bifidobacteria and Butyrate-Producing Colon Bacteria: Importance and Strategies for Their Stimulation in the Human Gut

With the increasing amount of evidence linking certain disorders of the human body to a disturbed gut microbiota, there is a growing interest for compounds that positively influence its composition and activity through diet. Besides the consumption of probiotics to stimulate favorable bacterial communities in the human gastrointestinal tract, prebiotics such as inulin-type fructans (ITF) and arabinoxylan-oligosaccharides (AXOS) can be consumed to increase the number of bifidobacteria in the colon. Several functions have been attributed to bifidobacteria, encompassing degradation of non-digestible carbohydrates, protection against pathogens, production of vitamin B, antioxidants, and conjugated linoleic acids, and stimulation of the immune system. During life, the numbers of bifidobacteria decrease from up to 90% of the total colon microbiota in vaginally delivered breast-fed infants to <5% in the colon of adults and they decrease even more in that of elderly as well as in patients with certain disorders such as antibiotic-associated diarrhea, inflammatory bowel disease, irritable bowel syndrome, obesity, allergies, and regressive autism. It has been suggested that the bifidogenic effects of ITF and AXOS are the result of strain-specific yet complementary carbohydrate degradation mechanisms within cooperating bifidobacterial consortia. Except for a bifidogenic effect, ITF and AXOS also have shown to cause a butyrogenic effect in the human colon, i.e., an enhancement of colon butyrate production. Butyrate is an essential metabolite in the human colon, as it is the preferred energy source for the colon epithelial cells, contributes to the maintenance of the gut barrier functions, and has immunomodulatory and anti-inflammatory properties. It has been shown that the butyrogenic effects of ITF and AXOS are the result of cross-feeding interactions between bifidobacteria and butyrate-producing colon bacteria, such as Faecalibacterium prausnitzii (clostridial cluster IV) and Anaerostipes, Eubacterium, and Roseburia species (clostridial cluster XIVa). These kinds of interactions possibly favor the co-existence of bifidobacterial strains with other bifidobacteria and with butyrate-producing colon bacteria in the human colon.