RESUMEN

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.

RESUMEN

We studied the impact of malting on barley starch gelatinisation properties and whether observed differences are due to changes in extrinsic or intrinsic factors. We isolated the total starch and large and small starch granules fractions from barley and malt samples and subjected them to DSC. The peak gelatinisation temperature for malt starch was, on average, 1.2 °C higher than for barley starch. The malting process and endosperm breakdown products were each responsible for half of this difference. The presence of water-extractable, non-starch components (sugars, minerals, protein and starch hydrolysis products,…) increased the intrinsic starch gelatinisation temperatures by 2.2-4.7 °C for barley and 3.6-5.3 °C for malt. The small starch granule fractions from barley had a 3.1 °C higher peak gelatinisation temperature than large granule fractions. No effect of malting was observed here. These findings indicate that matrix effects and starch granule size must be considered when addressing starch conversion during brewing.

Asunto(s)

RESUMEN

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.

Asunto(s)

RESUMEN

To obtain an efficient conversion of starch into fermentable sugars and dextrins during the brewing process, mashing time-temperature profiles need to promote starch gelatinisation and enzyme activity while avoiding thermal inactivation of the amylases. This study focused on the second part of this balance by investigating the thermal stability of α-amylase and ß-amylase of Planet barley malt throughout mashing. Thermal inactivation in wort was modelled for both enzymes resulting in the estimation of thermal inactivation kinetic parameters such as rate constant of thermal inactivation kT (the rate of thermal inactivation of an enzyme at a constant temperature), activation energy for thermal inactivation Ea, decimal reduction time DT (the time needed to inactivate 90% of the enzyme activity at a given temperature) and the z-value. First-order inactivation was observed for α-amylase. For ß-amylase, fractional conversion inactivation occurred with a residual fraction of 13% of the ß-amylase activity that remained after prolonged heating at 72.5 °C. The ß-amylase protein population hence seems to consist of thermolabile and thermostable isoforms. The kinetic parameters for thermal inactivation of the enzymes were used to predict their residual activities throughout a laboratory-scale mashing process. The predicted residual activities met the experimentally determined residual enzyme activities closely, except for ß-amylase at temperatures higher than 72.5 °C. The results obtained in this work allow designing new mashing processes or tailoring existing processes towards variability in the input material, barley malt, without the need for trial-and-error experiments.

Asunto(s)

RESUMEN

Hydrolysis of starch is key in several industrial processes, including brewing. Here, the activity and inactivation kinetics of amylases throughout barley malt mashing are investigated, as a prerequisite for rational optimisation of this process. Varietal differences were observed in the activity of α- and ß-amylases as a function of temperature for six barley and malt varieties. These differences were not reflected in the resulting wort composition after mashing, using three isothermal phases of 30 min at 45 °C, 62 °C and 72 °C with intermediate heating by 1 °C/min. Thermal inactivation kinetics parameters determined for α- and ß-amylases of an industrially relevant malt variety in a diluted system showed that enzymes were inactivated at lower temperatures than expected. The obtained kinetic parameters could predict α-amylase, but not ß-amylase inactivation in real mashing conditions, suggesting that ß-amylase stability is enhanced during mashing by components present or formed in the mash.

Asunto(s)

RESUMEN

While arabinoxylans (AX), an important dietary fiber fraction of wheat-based broiler diets, are known for exerting antinutritional effects in the gastrointestinal (GI) tract of broilers, the prebiotic potential of arabinoxylan-oligosaccharides (AXOS) is also well-documented. However, inconsistent performance responses as well as the effectiveness of low amounts of AXOS used in diets of previously conducted experiments put into question the classical prebiotic route being the sole mode of action of AXOS. The objective of this study was to investigate the effects of dietary AXOS addition on the rate of AX digestion in the gastrointestinal tract of broilers as a function of broiler age to gain more insight into the mode of action of these oligosaccharides. A feeding trial was performed on 480 one-day-old chicks (Ross 308) receiving a wheat-based diet supplemented with or without 0.50% AXOS, containing no endoxylanases. Digesta samples from ileum and caeca and fecal samples were analyzed for AX content, AX digestibility, intestinal viscosity, and microbial AX-degrading enzyme activities at 6 different ages (day 5, 10, 15, 21, 28, 35). Chicks fed from hatching with 0.50% AXOS demonstrated a higher ileal viscosity (P < 0.05). Also higher levels of AX solubilization and fermentation compared to control birds at 10 D were observed. This was noted by the higher total tract AX digestibility of water-extractable AX (WE-AX) and total AX (TOT-AX) at this age (P < 0.05). Although no significant difference in AX-degrading enzyme activities was observed among the dietary treatments, AXOS supplementation in young broilers was shown to stimulate or "kick-start" dietary AX digestion, thereby speeding up the development of a fiber-fermenting microbiome in the young broiler. This stimulation effect of AXOS could enable greater functional value to be extracted from dietary fiber in broiler feeds.

Asunto(s)

RESUMEN

The proportion of small and large starch granules in barley and malt is often neglected, leading to underestimation of their importance in processes in which they are used. This study aimed to accurately determine the volume and number based percentages of small and large starch granules for three barley varieties, their micro-malted malts and three commercial malts. Quantitative starch isolation was performed and starch granule proportions were estimated using microscopic and image analysis, taking the non-sphericity of the large starch granules into account. Results show that barley starch consists of 32-39 volume% of small starch granules. Upon malting, this percentage is reduced to 17-27 volume%, showing that small granules are hydrolyzed faster than large granules during this process. The analyzed commercial malt samples have a small starch granule content of 22-25 volume%. Malt hence still contains a substantial amount of small starch granules, which can be expected to impact processing.

Asunto(s)

RESUMEN

Endoxylanases are frequently used in cereal-based broiler feeds to improve the nutritional quality of the feed. It is hypothesized that the age of broilers and the age-related development of their intestinal microbiota influence the efficacy of these enzymes. Hence, the objective of this study was to identify possible age-related changes in arabinoxylan (AX) digestion in the different parts of the gastrointestinal (GI) tract of broilers. A feeding trial was performed with 240 1-day-old chicks (Ross 308) receiving a wheat-based feed containing no supplemented endoxylanase. Digesta samples from every section of the GI tract were collected at 5, 10, 15, 21, 28, and 35 d of age and analyzed for AX content, AX digestibility, intestinal viscosity, and microbial endoxylanase and arabinofuranosidase activities. In the first 2 wk, the microbiota were able to solubilize a part of the water-unextractable arabinoxylan (WU-AX), thereby increasing intestinal viscosity and water-extractable arabinoxylan (WE-AX) concentrations in the GI tract. In these young birds, WU-AX and WE-AX with low arabinose to xylose ratios were able to enter the caeca but were not yet extensively fermented by the caecal microbiota as indicated by the high caecal AX concentrations at 5 and 10 d (P < 0.01). Establishment of a more mature microbial community at 3 wk of age resulted in a further increase in both the solubilization of WU-AX and fermentation of WE-AX at the ileum and caecum (P < 0.10). Furthermore, the increase in AX degrading enzyme activities with age denotes the high AX degrading capacity of the caecal microbiota. Finally, a total tract AX digestion of 24% was achieved at slaughter age (day 35). Our results clearly indicate that the capacity of intestinal microbiota to degrade AX in the hindgut increases as the broiler ages. This suggests that the benefits of endoxylanase supplementation of broiler feeds depend on the interaction of the intestinal microbiota and AX present in the GI tract at specific broiler ages.

Asunto(s)

RESUMEN

This study investigates the effect of the physical presence and water binding of wheat bran during bread making, and the possible mechanisms behind this effect. Regular bran, pericarp-enriched bran and synthetic bran-like particles with different water binding capacities and particle sizes were used. Incorporation of regular and pericarp-enriched bran in dough (15% dm) led to a lower oven rise than the control dough. Bread volumes decreased with 11% and 30%, respectively. Dough with synthetic bran, having a low water binding capacity, displayed a near to normal leavening and oven rise and resulted in a bread volume decrease of only 5% compared to the control. Particle size reduction of regular bran and synthetic bran to an average size of 200 µm did not affect final bread quality. Results indicate that water binding by bran affects bread quality the most, whereas steric hindrance by physical presence of bran particles is less determinative.

Asunto(s)

RESUMEN

In this study, the molecular mobility of water and biopolymers in coarse, ground, and pericarp-enriched (PE) wheat bran and refined flour was investigated using time-domain proton nuclear magnetic resonance relaxometry, and related to their hydration properties. Several specific proton populations were present in the bran samples but not in flour. These populations were mainly assigned to protons of bran-related compounds such as arabinoxylan, cellulose, and lipids. All bran samples showed similar proton distributions at a 44% moisture level, although the chemical composition of coarse/ground bran and PE bran differed. When bran was further moistened up to 80%, an additional, more mobile water peak was noticed in coarse and PE bran, but not in ground bran. This can be explained by the fact that coarse and PE bran hold more weakly bound water than ground bran, which is most probably water entrapped in between bran particles.

Asunto(s)

RESUMEN

Water binding is suggested to be key in the deleterious effect of wheat bran on bread quality. This study investigates water mobility and biopolymer behavior during bran-rich bread making and storage, using 1H NMR. Coarse, ground, and pericarp-enriched bran were incorporated in bread dough, and their impact on freshly baked and stored bread properties was assessed. Compared to wheat flour control dough, bran incorporation resulted in a progressive immobilization of water during dough resting, which could be linked to changes in evolution of dough height during fermentation and oven rise. This, together with modified starch gelatinization behavior upon baking, can be related with the inferior quality of bran-rich breads. The impact was most pronounced with pericarp-enriched bran. Textural quality during storage was less affected for coarse or ground bran-rich bread compared to wheat flour bread, which could be principally attributed to retardation of amylopectin retrogradation in the presence of bran.

Asunto(s)

RESUMEN

Feed additives, including prebiotics, are commonly used alternatives to antimicrobial growth promoters to improve gut health and performance in broilers. Wheat bran is a highly concentrated source of (in)soluble fiber which is partly degraded by the gut microbiota. The aim of the present study was to investigate the potential of wheat bran as such to reduce colonization of the cecum and shedding of Salmonella bacteria in vivo. Also, the effect of particle size was evaluated. Bran with an average reduced particle size of 280µm decreased levels of cecal Salmonella colonization and shedding shortly after infection when compared to control groups and groups receiving bran with larger particle sizes. In vitro fermentation experiments revealed that bran with smaller particle size was fermented more efficiently, with a significantly higher production of butyric and propionic acid, compared to the control fermentation and fermentation of a larger fraction. Fermentation products derived from bran with an average particle size of 280µm downregulated the expression of hilA, an important invasion-related gene of Salmonella. This downregulation was reflected in an actual lowered invasive potential when Salmonella bacteria were pretreated with the fermentation products derived from the smaller bran fraction. These data suggest that wheat bran with reduced particle size can be a suitable feed additive to help control Salmonella infections in broilers. The mechanism of action most probably relies on a more efficient fermentation of this bran fraction and the consequent increased production of short chain fatty acids (SCFA). Among these SCFA, butyric and propionic acid are known to reduce the invasion potential of Salmonella bacteria.

Asunto(s)

RESUMEN

Liquid reductive processing of birch wood in the presence of commercial Ru/C or Pd/C catalysts yields about 50% of a select set of phenolic monomers and a variety of phenolic di- and oligomers, next to a solid carbohydrate pulp. Changing the catalyst from Ru/C to Pd/C drastically increases the OH-content of the lignin-derived products, in particular for the phenolic monomers.

Asunto(s)

RESUMEN

About 70% of the protein for human consumption is derived from plants, with cereals as the most important source. Wheat bran protein has a more balanced amino acid profile than that of flour. We here for the first time report the amino acid, size exclusion, and SDS-PAGE profiles of bran Osborne protein fractions (OPFs). Moreover, we also investigated how OPFs are affected when physical barriers which entrap proteins in bran tissues are removed. Albumin/globulin is the most abundant OPF. It is richer in lysine and asparagine/aspartic acid than other OPF. Most bran albumin/globulin proteins have a molecular weight (MW) lower than 30 k and their chromatographic profiles differ from those of flour. The prolamin has high levels of proline and glutamine/glutamic acid. It is rich in proteins with a MW of 30 to 45 k and about 66 k reflecting contamination with gliadin from endosperm. The glutelin has high levels of glycine, proline, and glutamine/glutamic acid. Its protein is of intermediate and high MW with little protein with MW lower than 30 k. The high (MWs from 80 to 120 k) and low (MW around 45 k) MW glutenin subunits of flour are also present in bran. The glutelin of wheat endosperm is named glutenin. Ball milling releases albumin/globulin and glutelin but not prolamin. Not all glutelin was endosperm glutenin as a substantial part was entrapped in the aleurone cells.

Asunto(s)

RESUMEN

Moisture migration largely impacts cake crumb firmness during storage at ambient temperature. To study the importance of phenomena other than crumb to crust moisture migration and to exclude moisture and temperature gradients during baking, crustless cakes were baked using an electrical resistance oven (ERO). Cake crumb firming was evaluated by texture analysis. First, ERO cakes with properties similar to those baked conventionally were produced. Cake batter moisture content (MC) was adjusted to ensure complete starch gelatinisation in the baking process. In cakes baked conventionally, most of the increase in crumb firmness during storage was caused by moisture migration. Proton nuclear magnetic resonance ((1)H NMR) showed that the population containing protons of crystalline starch grew during cake storage. These and differential scanning calorimetry (DSC) data pointed to only limited amylopectin retrogradation. The limited increase in amylopectin retrogradation during cake storage cannot solely account for the significant firming of ERO cakes and, hence, other phenomena are involved in cake firming.

Asunto(s)

RESUMEN

Based on a model system approach, five different proton populations were distinguished in pound cake crumb using one dimensional low resolution (1)H NMR spectroscopy. In free induction decay (FID) measurements, proton populations were assigned to (i) non-exchanging CH protons of crystalline starch, proteins and crystalline fat and (ii) non-exchanging CH protons of amorphous starch and gluten, which are in little contact with water. In Carr-Purcell-Meiboom-Gill (CPMG) measurements, three proton populations were distinguished. The CPMG population with the lowest mobility and the FID population with the highest mobility represent the same proton population. The two CPMG proton populations with the highest mobility were assigned to exchanging protons (i.e., protons of water, starch, gluten, egg proteins and sugar) and protons of lipids (i.e., protons of egg yolk lipids and amorphous lipid fraction of margarine) respectively. Based on their spin-lattice relaxation times (T1), two dimensional (1)H NMR spectroscopy further resolved the two proton populations with the highest mobility into three and two proton populations, respectively.

Asunto(s)

RESUMEN

Maltogenic α-amylase from Bacillus stearothermophilus (BStA) is widely used as bread crumb anti-firming enzyme. A maltotetraose-forming α-amylase from Pseudomonas saccharophila (PSA) was recently proposed as alternative, hence the need to compare both exo-acting enzymes with some endo-action component. A purely exo-acting thermostable ß-amylase from Clostridium thermosulfurogenes (CTB) was included for reference purposes. Under the experimental conditions used, temperature optima of the enzymes are rather similar (60-65 °C), but temperature stability decreased in the order BStA, PSA and CTB. The action of the enzymes on different substrates and their impact on the rheological behaviour of maize starch suspensions demonstrated that, while CTB acts exclusively through an exo-action mechanism, BStA displayed limited endo-action which became more pronounced at higher temperatures. PSA has more substantial endo-action than BStA, which is rather temperature independent. This is important for their impact in processes such as breadmaking, where temperature is gradually increased.

Asunto(s)

RESUMEN

AIMS: To search for nondigestible but fermentable (NDF) carbohydrates and prebiotics with a potency to promote the growth of selected bacteria in vitro. METHODS AND RESULTS: The growth of three reference bacteria strains Bacillus subtilis LMG 7135(T), Carnobacterium piscicola LMG 9839, Lactobacillus plantarum LMG 9211 and one candidate probiotic bacteria Lactobacillus delbrueckii subsp. lactis was investigated over a minimum period of 48 h in the presence of beta-glucan, xylo-oligosaccharide, arabinoxylo-oligosaccharide, inulin, oligofructose and glucose. Besides the capability to grow on inulin and oligofructose containing media, a distinct high growth in beta-glucan based substrates and a low growth in (arabino)xylooligosaccharide containing media were evident for most bacteria tested. With the exception of B. subtilis and L. plantarum, other bacteria grew equally well or even better on different substrates than on glucose. The fermentation of studied carbohydrates by these micro-organisms was dominated by the production of acetic acid as the main short chain fatty acid. CONCLUSIONS: Selected bacteria are able to ferment and grow on NDF and prebiotic carbohydrates but in a substrate dependent manner. SIGNIFICANCE AND IMPACT OF THE STUDY: This study delivers a first screening of which NDF or prebiotic carbohydrates are the most promising for aquaculture feed supplementations.

Asunto(s)

RESUMEN

Arabinoxylan-oligosaccharides (AXOS) are a recently newly discovered class of candidate prebiotics as - depending on their structure - they are fermented in different regions of gastrointestinal tract. This can have an impact on the protein/carbohydrate fermentation balance in the large intestine and, thus, affect the generation of potentially toxic metabolites in the colon originating from proteolytic activity. In this study, we screened different AXOS preparations for their impact on the in vitro intestinal fermentation activity and microbial community structure. Short-term fermentation experiments with AXOS with an average degree of polymerization (avDP) of 29 allowed part of the oligosaccharides to reach the distal colon, and decreased the concentration of proteolytic markers, whereas AXOS with lower avDP were primarily fermented in the proximal colon. Additionally, prolonged supplementation of AXOS with avDP 29 to the Simulator of Human Intestinal Microbial Ecosystem (SHIME) reactor decreased levels of the toxic proteolytic markers phenol and p-cresol in the two distal colon compartments and increased concentrations of beneficial short-chain fatty acids (SCFA) in all colon vessels (25-48%). Denaturant gradient gel electrophoresis (DGGE) analysis indicated that AXOS supplementation only slightly modified the total microbial community, implying that the observed effects on fermentation markers are mainly caused by changes in fermentation activity. Finally, specific quantitative PCR (qPCR) analysis showed that AXOS supplementation significantly increased the amount of health-promoting lactobacilli as well as of Bacteroides-Prevotella and Clostridium coccoides-Eubacterium rectale groups. These data allow concluding that AXOS are promising candidates to modulate the microbial metabolism in the distal colon.

Asunto(s)

RESUMEN

The objective of this in vivo experiment was to evaluate the influence of arabinoxylooligosaccharides (AXOS) on shedding and colonization of Salmonella Enteritidis in broilers. Arabinoxylooligosaccharides, which are oligosaccharides derived from arabinoxylans by partial hydrolysis, have a beneficial effect on feed conversion ratios when added to broiler diets. Additionally, AXOS have been shown to promote the growth of bifidobacteria in the cecocolonic compartment of the gastrointestinal tract. To investigate the impact of AXOS on colonization of broilers with Salmonella, 224 one-day-old chicks were divided into 4 groups and given either unsupplemented feed or feed supplemented with 0.2% AXOS-3-0.25, 0.2% AXOS-9-0.25, or 0.4% AXOS-9-0.25 throughout the experiment. The AXOS-3-0.25 and AXOS-9-0.25 both have an ara-binose-to-xylose ratio of 0.25 and have an average degree of polymerization of 3 and 9, respectively. At 14 d posthatch, each animal was orally inoculated with 2.5 x 10(9) cfu of Salmonella Enteritidis. Cloacal swabs, taken at regular times, showed a significant reduction of Salmonella presence in the group given 0.4% AXOS-9-0.25 compared with the control group. This reduction was observed in the 1- to 11-d postinfection period. Colonization of the ceca as well as the translocation of Salmonella to the spleen was significantly reduced at 3 and 7 d postinfection in the 0.4% AXOS-9-0.25 group. A similar, although more moderate, decrease in colonization was observed in the group given 0.2% AXOS-9-0.25. It was concluded that dietary addition of AXOS provides dose-dependent protection against oral infections with Salmonella Enteritidis in poultry.

Asunto(s)