1,721,071 research outputs found
Replication Data for: Pearl millet (Pennisetum glaucum) couscous breaks down faster than wheat couscous in the Human Gastric Simulator, though has slower starch hydrolysis
No full textThis data is for a study on millet couscous gastric (stomach) simulation and emptying. The basis for this research was a previous human crossover study we did in Mali showing that traditional starchy foods made from millet and sorghum (millet and sorghum thick porridges, and millet couscous) had gastric half-emptying times that were about twice as long as other non-traditional foods (white rice, boiled white potato, well-cooked wheat-based pasta). Here, we investigated the reasons for the slow gastric emptying of millet couscous. The dataset is an Excel spreadsheet containing simulated gastric data on different couscous samples as described in the publication cited below. The data spreadsheet also includes viscosity data ("RVA" tab) and chromatography molecular size data for starch ("HPSEC" tab)
Development and functional characterization of new antioxidant dietary fibers from pomegranate, olive and artichoke by-products
No full textA novel ingredient acting as a slow digestible dietary fiber (DF) was developed by including native corn starch in calcium alginate microspheres (MS). In this study three types of antioxidant DF-rich ingredients were designed and developed by including in the MS, polyphenol-rich vegetable by-product extracts (obtained from pomegranate peels, olive leaves and artichoke leaves) and their potential functionality was assessed in vitro.
Specifically, the physico-chemical properties of the new MS were compared with those of six commercially available DF concentrates and with wheat and oat brans. To evaluate the potential efficacy to release PPs along the gastrointestinal tract (GiT), pomegranate peels-microspheres (PPe-MS) were subjected to in vitro simulated gastrointestinal digestion. Results showed that the newly developed MS had higher free antioxidant capacity (free-TAC) than commercial DF rich products, and the bound antioxidant capacity (bound-TAC) of PPe-MS was comparable to that of wheat bran and 4.4 folds higher than that of oat-bran. Furthermore, it was shown that the release of ellagitannins from cooked PPe-MS along in vitro simulated gastro-intestinal digestion decreased from the salivary to the small intestine phase whereas gallic acid, ellagic acid and its derivatives had an opposite trend. A certain amount of PPs was found in the spent pellet obtained from the in vitro digestion, which was mimicking the residue reaching the colon in vivo. In conclusion data showed that the new antioxidant MS have physical-chemical properties like those of wheat and oat brans, mainly including the bound antioxidant capacity. This open to new possibilities of functional utilization of vegetable by-products for obtaining valuable and healthy food ingredients
Fabrication of Model Plant Cell Wall Materials to Probe Gut Microbiota Use of Dietary Fiber
No full textThe cell wall provides a complex and rigid structure to the plant for support, protection from environmental factors, and transport. It is mainly composed of polysaccharides, proteins, and lignin. Arabinoxylan (AX), pectin (P), and cellulose (C) are the main components of cereal cell walls and are particularly concentrated in the bran portion of the grain. Cereal arabinoxylans create networks in plant cell walls in which other cell wall polysaccharides are imbedded forming complex matrices. These networks give an insolubility profile to plant cell wall. A previous study in our lab showed that soluble crosslinked arabinoxylan with relatively high residual ferulic acid from corn bran provided advantageous in vitro human fecal fermentation products and promoted butyrogenic gut bacteria. In the present work, arabinoxylan was isolated from corn bran with a mild sodium hydroxide concentration to keep most of its ferulic acid content. Highly ferulated corn bran arabinoxylan was crosslinked to create an insoluble network to mimic the cereal grain cell wall matrices. Firstly, arabinoxylan film (Cax-F), pectin film (P-F), the film produced by embedding pectin into arabinoxylan networks (CaxP-F), and cellulose embedding arabinoxylan matrices (CaxC-F), and embedding the mixture of cellulose and pectin into arabinoxylan networks (CaxCP-F) were fabricated into simulated plant cell wall materials. Water solubility of films in terms of monosaccharide content was examined and revealed that Cax-F was insoluble, and P-F was partially insoluble, and nanosized pectin and cellulose were partially entrapped inside the crosslinkedarabinoxylan matrices. In a further study, these films were used in an in vitro human fecal fermentation assay to understand how gut microbiota access and utilize the different simulated plant cell walls to highlight the role of each plant cell wall component during colonic fermentation. In vitro fecal samples, obtained from three healthy donors were used to ferment the films (Cax-F, P-F, CaxP-F, CaxC-F, and CaxCP-F) and controls (free form of cell wall components -Cax, P and C). The fabricated films that were compositionally similar to cell walls were fermented more slowly than the free polysaccharides (Cax and P). Besides, CaxP-F produced the highest short chain fatty acids (SCFA) amount among the films after 24 hour in vitrofecal fermentation. Regarding specific SCFA, butyrate molar ratio of all films was significantly higher than the free, soluble Cax and P. 16S rRNA gene sequencing explained the differences of the butyrate proportion derived from specific butyrogenic bacteria. Particularly, some bacteria, especially in a butyrogenic genera from Clostridium cluster XIVa, were increased in arabinoxylan films forms compared to the native free arabinoxylan polysaccharide. However, no changes were observed between P and P-F in terms of both end products (SCFA) and microbiota compositions. Moreover, CaxP-F promoted the butyrogenic bacteria in fecal samples compared with pectin alone, arabinoxylan alone, and the arabinoxylan film. Differences in matrix insolubility of the film, which was high for the covalently linked arabinoxylan films, but low for the non-covalent ionic-linked pectin film, appears to play an important role in targeting Clostridial bacterial groups. Overall, the cell wall-like films were useful to understand which bacteria degrade them related to their physical form and location of the fiber polymers. This study showed how fabricated model plant cell wall films influence specificity and competitiveness of some gut bacteria and suggest that fabricated materials using natural fibers might be used for targeted support of certain gut bacteria and bacterial groups
Structural features of cereal bran arabinoxylans related to colon fermentation rate
No full textSoluble and fermentable fibers provide numerous benefits to host health due to the production of short chain fatty acids. Gas produced during fermentation is a concern of fermentable fiber intake, causing bloating and flatulence in commercial prebiotics such as fructooligosaccharides. Alkali-extractable arabinoxylans from various cereal brans have shown different fermentation patterns. Fiber with initial slow and complete fermentation is desirable both to overcome the problem of gas production and to provide fermentable substrate to the mid and distal colon. In this study, three different types of modifications have been conducted to investigate the factors that slow initial rate of fermentation, as well as provide some extent of extended fermentation. First, enzymatic modification with endoxylanase and graded ethanol precipitation were used to obtain alkali-extractable arabinoxylans in varying molecular size, degree of substitution, and degree of branching indicated by the arabinose:xylose ratio. Molecular size, degree of substitution, and arabinose:xylose ratio of highly branched arabinoxylans showed no relationship to fermentation patterns. The linkage-type of the branches was the major structural feature of highly branched arabinoxylans that promoted slow fermentation. Branches containing single xylose units were the most significant in this regard, followed by oligosaccharide side chains with two second level sugars linked at O-2,3 of the arabinose residues. Oligosaccharide side chains with the second sugar (xylose, arabinose, or galactose) linked at O-2, O-3, and O-5 of the arabinose residues were the least important with respect to slow fermentation. Second, chemical modification by acid and graded ethanol precipitation was performed to produce arabinoxylooligosaccharides hypothesized to have slow fermenting linkages identified above. However, all acid-hydrolyzate fractions were fermented rapidly, caused by the loss of all single arabinose unit side chains and some di/trisaccharides side chains. In this case, the degree of substitution and type of linkage of the branched constituents affected the rate of fermentation more than the degree of polymerization. Third, mechanical modification (ball milling) was applied to obtain smaller arabinoxylan structures, and confirmed that fermentation rate is influenced by the quantity and type of linkage of the branched constituents rather than molecular size and showed that smaller arabinoxylan polymers retained both branch linkages and the slow fermentation property. The application of alkali-extractable corn arabinoxylan and its hydrolyzate in foods was also tested. Only corn xylanase-treated hydrolyzate had both a high pH and heat stability, low shear thinning viscosity and only slightly discolored solutions, giving it the potential to be used in high fiber drinks while retaining beneficial initial low gas production and extended fermentation
Traditional and modern oat-based foods
No full textOats have traditionally been used mainly as oatmeal, bran or flakes, which are used to produce porridge, bread and breakfast cereals. Apart from porridge, which can be made from 100% oats, in most consumer products oats are added as an ingredient, to provide increased customer value. Most of the novel oat ingredients are bran or β-glucan-enriched oat fractions. Furthermore, in addition to the health-promoting and technologically versatile fiber fraction, oats contains high amount of fats with nutritionally beneficial fatty acid and lipid class composition, proteins rich in valuable amino acids, and unique phenolic compounds, such as avenanthramides, among other minor nutrients. However, only a small minority of oat crops is processed to food and other valuable products, and most of the harvested oats are used for animal feeding purposes. The kinetics of β-glucan solubility and the tendency to form very viscous shear thinning gels varies in different oat products. Thus, modern oat ingredients are suitable for various types of food applications without the adverse effects that were evident in conventional oat products. These novel ingredients are available in various forms with different composition, appearance and taste, and different technological functionality. This chapter introduces oats as a food raw material, its composition and its technological properties. It presents different types of oat products and some examples of production technologies, summarizes current knowledge on the health-promoting effects of oats, and discusses the future trends for oat products. Oat products are divided into traditional and novel oat products.<br/
Manipulation of zein structure with co-protein addition for application in dough systems
No full textGluten, wheat storage protein, exhibits unique ability of forming a viscoelastic dough upon hydration and mixing. It is composed of alcohol soluble proteins, gliadins, and polymeric glutenins. The interactions between gluten proteins, gliadins and glutenins, are responsible for the formation of viscoelastic protein network. Gliadins are recognized as the protein fractions responsible for viscous nature of gluten and, glutenins for the elasticity. High molecular weight subunits of glutenin (HMW-GS) have been found particularly important in imposing elasticity to gluten structure. The mechanism involves the structural transitions between β-sheet and β-turns and is related to the long repeat regions of HMW-GS and their interactions. On the other hand, corn protein, zein, is relatively small protein and does not demonstrate viscoelastic properties at room temperature. However, α-zein was shown to form viscoelastic dough at moisture contents larger than 20% when hold and mixed at 35°C, which is above its glass transition temperature. Here, it is speculated that gliadin, which comprises significant portion of wheat gluten, is not only simply a filler imparting viscosity to wheat gluten, but also an important functional protein fraction that goes through structural transformation with addition of HMW-GS to the system. Therefore, it is hypothesized that, zein, which shows similarities to wheat gliadin in number of aspects, can attain viscoelastic properties at room temperature with addition of co-protein similar to that of HMW-GS in wheat gluten. Wheat and corn proteins were utilized in this study to investigate and compare their viscoelastic properties. Fundamental rheological techniques and Fourier Transform InfraRed (FT-IR) spectroscopic studies were performed to understand the structure-function relationship in these proteins. Improved viscoelastic properties were obtained for zein with addition of co-protein at room temperature. The transformation of gliadin with the addition of HMW-GS and glutenin was also shown. However, gliadin and zein were found to gain structural functionality through different mechanisms. In gliadin, structural transformation took place through transitions between β-sheet and β-turns. On the other hand, main transition in zein was found to be from α-helix to β-sheet
Physicochemical properties of corn flour and starch and their relation to gel texture of two dry-milled fractions
No full textTen corn cultivars with different kernel density and hardness scored were dry-milled to separate the grit and flour fractions. Causal relationships between physicochemical properties of corn flour and starch and their respective gel textural attributes were investigated. Texture profile analysis revealed that substantial differences were found in gel texture among ten corn Cultivars. Also, both flour and starch gels in the grit fraction had much higher values for hardness, guminess and chewiness than their flour counterparts. Starch gels were positively correlated with flour gel hardness in both dry-milled fractions implying that starch is a major determinant of gel texture. The influence of starch on the texture characteristics of starch and flour gels from the dry-milled grit and flour fractions appeared to be related to the fine structural differences of amylopectins. Starch from the grit fraction with higher amount of long chain amylopectin (DPn 70-75) was shown to significantly and positively correlate with stronger flour and starch gels from this fraction. Among the ten corn cultivars, amylose content determined from size exclusion chromatography was significantly correlated with textural parameters of starch gels from both two dry-milled fractions. We found that the thermal parameters of gelatinization and retrogradation revealed by differential scanning calorimetry (DSC) were also related to amylopectin structure. Both the onset temperature (To) and enthalpy (H) of gelatinization were positively correlated with the amount of the long chains (DPn 70-75) and negatively correlated with the extent of chain branching of the amylopectin. The enthalpy (H) of retrogradation was positively correlated with the proportion of the long chains and average chain length of the amylopectin among the ten corn cultivars. This study also showed that gelatinization and retrogradation properties of starch and flour correlated to some aspects of gel texture, particularly gel hardness. The findings suggest that fine structure of amylopectin, including chain length distribution, chain branching and average chain length, affects the crystalline structure of native starch and retrogradation of gelatinized starch. These genotypic and kernel spatial differences in starch structure have not been shown prior to this report and could have significant impact on those trying to tailor make corn flours and starches for precise applications in the food industry
Influence of the structural complexity of cereal arabinoxylans on human fecal fermentation and their degradation mechanism by gut bacteria
No full textCereal arabinoxylans from different sources have been found to possess a large structural heterogeneity and generate different fermentation profiles. Among them, corn arabinoxylan is a relatively homogeneous polymer group and has an initial slow fermentation property. A high level of complex branches containing terminal xylose and terminal galactose, other than the commonly existing terminal arabinose, have been identified in corn arabinoxylan and correlated to its slow fermentation property. Structural models of corn arabinoxylan relating to fermentation were previously proposed, but without considering possible distribution patterns of the various branches that may play an important role in determining its fermentation property. Therefore, the first objective of this study was to establish a more accurate structural model for corn arabinoxylan to explain its slow fermentation property. A highly organized structural feature of multiple layers was revealed for corn arabinoxylan for the first time, in which the complex branches assemble to form regions that are connected by simply-branched parts, and the complex-branched regions containing further sub-layers. The structural subunits containing high levels of complex branches were found to act as the functional parts of corn arabinoxylan with different slow fermentation properties. Based on the new structural model, a range of corn arabinoxylan-based fiber molecules (14 fractions) were produced by different enzymatic treatments and were fermented using human fecal microbiota. Differences in fermentation rates revealed a sensitive response of gut microbiota to subtly different structural features within one fiber polymer. To investigate the involved mechanisms of digestion, an idealized experimental model was designed using Bacteroides pure strains. Specific molecular regions of dietary fibers were found to differentiate xylanolytic Bacteroides growth and influence their competition patterns. While a most complex corn arabinoxylan structural region made one strain of B. cellulosylitcus (DSM 14830) outcompete a strain of B. ovatus (3-1-23), a more generalized lightly branched structure favored the latter strain. It is speculated that each bacteria type in the colon may have a substrate structure specific for itself, whereby it can be utilized to specifically favor its growth in the competitive environment of the colon. Moreover, different degradation mechanisms were found within one Bacteroides strain using four substrates by monitoring the targeted gene expression profiles and structural changes of the remaining substrate and were based on the structural composition of fiber molecules. In conclusion, the slow fermentation property of corn arabinoxylan was caused by molecular regions consisting of high structural complexity. A subtle manipulation of the structural complexity of fiber molecules resulted in a considerable change in human colon fermentation property. Gut bacteria compete for the different regions of fiber molecules and are equipped with different enzyme degrading systems that target unique structural features, which were revealed in different degradation mechanisms for fiber molecules according to their structural compositions. This work furthers our knowledge of substrate specificity for gut bacteria, and suggests the possibility for more specific manipulation of the colon microbiota composition and fermentation property in a designed way
Amylopectin fine structure: Mechanism of the long chain function
No full textThe sole impact of amylopectin long chains and internal structure on its functional properties was the research topic of this thesis. Greater and broader enthalpic transitions, greater increase in storage modulus and a denser and tighter gel microstructure after retrogradation were found in waxy rice starches with slightly higher proportion of long chains, indicating that more extensive intermolecular interactions were formed. The internal long chains of amylopectin are suspected to contribute to these intermolecular interactions. As a prerequisite to this hypothesis, the ability of internal chains to accommodate iodine as a turned or helical structure is regarded as an indication that internal chains either naturally exist in a helical form or have the flexibility to move around and form helices. Waxy and ae waxy corn starches were hydrolyzed by β-amylase for varied periods of time and the resulting β-dextrins, and the native structure, were exposed to iodine solution. The absorbance and the maximum wavelength of the absorbance were recorded. Two possible scenarios were proposed for the iodine internal chain complexation: (1) only external chains of native amylopectin bind iodine and hydrolyzed external chains allow internal iodine binding and (2) both external and internal chains of native amylopectin bind iodine. From the viewpoints of both chain length and helical conformational structure, the internal chains have the ability to bind iodine either because they are naturally synthesized in a turned helical form or they assume the helical structure under certain conditions, i.e. the removal of the external chains of amylopectin. Detailed fine structure information was obtained on waxy and ae waxy corn starches by varied time β-amylolysis followed by full β-amylolysis and debranching. This provided an explanation of the iodine binding results from the fine structure perspective. The “backbone” model was discussed as possibly a better explanation of the influence of the long chains of amylopectin on its functional properties, because they would provide more flexibility to the chains for the intermolecular interconnections on retrogradation. Gain in a mechanistic understanding of amylopectin structure related to its functional properties, in this case the role of the long internal chains of amylopectin on functionality, provides further information on tailoring structures to fit desired textural and nutritional starch functions
Identification of novel starch and protein structures related to corn masa texture
No full textProduction of corn tortillas and tortilla chips first involves alkaline cooking of the kernels, followed by steeping and rinsing to yield smooth kernels known as nixtamal. Stone-milling the nixtamal generates the dough-like material known as mass, which is then sheeted and cut into the characteristic tortilla shapes. Masa should be adequately cohesive to resist breakage during rolling and sheeting, but not excessively adhesive so as to become sticky. The objective of this study was to identify specific chemical components within masa that are responsible for its cohesive/adhesive texture. Lime-concentration dependent complexation of proteins from heated lime:corn flour suspensions were observed using SDS-PAGE at concentrations above the saturation point of lime in solution. Another divalent ion-containing alkali, strontium hydroxide, produced a similar effect, while the effect of a monovalent ion-containing alkali was not as pronounced. Similar protein complexes were not readily apparent in masa. Gelatinized starch in nixtamal, estimated by β-amylase/pullulanase digestion, increased due to lime cooking from 11% to 16%. Intermediate pressure high-performance liquid chromatography (HPSEC) analysis of the water-soluble starch component from mass indicated that it increased in amount and molecular weight as cook time increased. This soluble fraction was similar to amylopectin with regard to λmax and isoamylase debranched profile, though of lower MW. It was termed “intermediate MW amylopectin-like component.” The amount of this component was highly correlated with masa adhesiveness (r = 0.890, P \u3c 0.01) and with cook time (r = 0.957, P \u3c 0.01). Amount of the intermediate MW amylopectin-like component was directly related to gap width of the stones in the masa mill and was concluded to be caused by amylopectin fragmentation due to shear force. Rapid detection of the intermediate MW amylopectin-like component can be achieved by using an iodine complexation assay. The results of this study strongly imply that the intermediate MW amylopectin-like component is the major determinant of masa texture and that its measurement can be used as a process control parameter
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