1,721,102 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)
Structural and Functional Properties of Enzymatically Modified Slow Digesting α-Glucans
No full textModerating glycemic response to foods is important for the potential to control or prevent hyperglycemia-related diseases, such as diabetes and cardiovascular disease. The importance of slowly digestible carbohydrates (SDC) lies in their health effects: moderated blood glucose response, and a potential for increased satiety and reduced intake, and weight management. The research presented is on structural properties of novel, mostly soluble, α-glucans (glucosecontaining oligomers and polymers with different linkage types and combinations) that are required for slow yet full digestion, and how they behave in food systems. Up to this point, little has been known regarding what structural properties of glucose-containing carbohydrates result in slow digestion, although starch structure has been well investigated and it is known that raw starch has a slowly digestible property. In addition to the structure-function aspect of the thesis work, this research contributes information about how α-glucan SDCs can be incorporated into food products that undergo heat treatment in the presence of moisture. The α-glucans maintain their SDC property while raw starch is gelatinized and becomes rapidly digestible. The rate of hydrolysis of a large number of novel α-glucans was studied using a simulated upper gastrointestinal in vitro digestion utilizing porcine pancreatic α-amylase and α-glucosidases from the rat intestine, and a subset was then evaluated in a crossover design clinical trial with blood glucose monitoring. Linkage and molecular weight analysis using gas chromatography of partially methylated alditol acetates and multi-angle light scattering and refractive index (MALS-RI) detection at time points during in vitro digestion were used to elucidate the relative rate of digestion of different linkage types in new and known α-glucan carbohydrates. Clinical results showed that resistant maltodextrin and reuteran had low initial glycemic profiles with no extended digestion, indicating rapid and resistant fractions; dextran and raw wheat starch had low initial glycemia and extended profiles, indicating a true SDC property; isomaltooligosaccharides and alternanooligosaccharides had high glycemic profiles; and alternan, as a larger polymer, was essentially undigested with a flat at-baseline glycemic profile. It was found that larger molecules with α-1,6, 1,3, and 1,2 linkages are generally more slowly digestible, though not always fully hydrolyzed within a 6 h upper GI in vitro digestion. Static and dynamic light scattering (SLS and DLS) showed the dextran sample to have a secondary structural conformation of branched or associated coils, and the Kratky plot confirmed this finding, indicating a molecular configuration of polydisperse coils likely contributing to a slow digestion rate.Rheological, turbidity, and SLS and DLS analyses were used to examine ingredient interaction between novel, enzymatically-modified α-glucans with slow digesting properties found most promising for inclusion in food products. A model nutritional beverage system was utilized containing proteins and salts. It was found that solvent and ion concentration of solutions were important for dictating aggregation formation with highly branched alternans and oligosaccharides in solution alone, or in the presence of soluble protein aggregates. Further, salts in solution proved to influence rheological and turbidity measures of all four α-glucans examined in the model system, indicating they may affect aggregation and structural conformation of such large carbohydrates. However, only tapioca maltodextrins showed in vitro rate of digestion affected by aggregation
Experimental and Clinical Investigations of Slowly Digestible Carbohydrates for Improved Physiological Outcomes and Metabolic Health
No full textThe world has experienced an unprecedented change in the systems responsible for food production, distribution, and commercialization with concurrent changes in diets. In developed and developing countries, the shift in consumption patterns has moved towards a Western diet pattern which has been linked to negative health outcomes including obesity, diabetes and associated non-communicable diseases. Traditional African diets have previously been associated with protective effects against the development of the above-mentioned conditions. Yet, the underlying reasons for this is not clear. One dietary factor that may contribute to its protective effect is the principal available carbohydrate, starch, which in traditional African staples is considered to contain slowly digestible carbohydrates (SDCs) and some amount of resistant starch (RS). We reported that traditional African staple starchy foods (sorghum and millet) had markedly slower gastric emptying than introduced modern starchy foods (rice, pasta and potatoes). This response was attributed to activation of enteroendocrine cells of the small intestine (L-cells) with potential to trigger physiological, hormonal, and neurological processes that affect digestion time and perception of hunger; effect known as the ileal brake. Moreover, at least in mice models, consumption of SDCs has shown to have beneficial effects on the rate and type of fuel (e.g. carbohydrate vs fat) used for metabolic processes.The first thesis study compared the effect of diets (cohorts in the USA and Kenya) on gastric half-emptying time and metabolic fuel utilization in healthy adults. Our findings showed that gastric emptying time was not different between cohorts and that diet did not influence gastric emptying time; however, calculated respiratory exchange ratio (RER) (which is a measure of metabolic fuel utilization at the cellular level, e.g. carbohydrate vs fat) and metabolic flexibility (which is the ability to switch between metabolic fuel sources upon demand or need) was higher for the Kenyan cohort. Multivariant models were developed and corrected for multicollinearity of some diet variables. Carbohydrate and protein in multivariate model 1; total fiber, added sugars and starch in multivariate model 2; and diet quality (measured as the Healthy Eating Index based on 2015-2020 dietary guidelines, or HEI-2015) in multivariate model 3, were significantly and independently correlated with RER and metabolic flexibility.The second study assessed if slow gastric emptying and improve metabolic fuel utilization could be induced through SDC supplementation. The objective of this study was to determine if continual consumption of SDC for 21 days delayed the rate of gastric emptying, moderated postprandial glycemic response, decreased hunger, and/or improved metabolic fuel utilization in subjects with low diet quality (HEI-2015\u3c65). Our results indicated that supplementation with SDC did not slow gastric emptying time or acute measures of metabolic fuel utilization; however, continuous consumption of SDC had a modest but significant effect on improving metabolic flexibility and decreasing hunger scores.The last two chapters of this thesis focused on the use of a low-cost, high-pressure, high temperature extruder suitable for processing in Africa of whole grain pearl millet (Pennisetum glaucum). In Africa, emerging, entrepreneurial companies are increasingly gaining share of local markets by manufacturing and distributing high-quality locally sourced processed foods made with indigenous grains. Whole pearl millet is particularly susceptible to development of rancidity
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Physical and Chemical Treatements of Zein to Improve Gluten-Free Bread Quality
No full textGluten is a complex mixture of proteins imparting unique viscoelastic properties to doughs. However, despite its outstanding role in producing high quality baked goods, gluten is also associated with health disorders such as celiac disease or gluten sensitivity. This generated an increased demand of gluten-free products as individuals suffering of gluten-related disorder need to follow a strict gluten-free diet. Zein is a gluten-free storage protein from corn possessing promising features for gluten replacement in breadmaking. Although numerous studies attempted to improve zein dough rheological properties to improve its breadmaking performance, zein bread making potential remain inferior if compared to gluten. When it is incorporated into a dough, zein can form fibrils which confers extensibility, however, it does not possess a strain hardening behavior, a fundamental feature to produce high quality bread.To improve zein dough strain hardening we hypothesize that structures formed by zein are not large enough to generate an elastic response, however the application of physicochemical treatment can induce the formation of broader structures better suited to store energy and therefore generate elasticity. Thus, the objective of this dissertation is to determine if dough viscoelastic properties essential for bread production can be obtained through the application of treatment favoring the formation of larger zein structures.Zein was electrospun using aqueous ethanol or acetic acid as solvent to form nanofibrils. Several additives were tested to enhance fibrils mechanical properties. Zein electrospun fibers were then incorporated into a dough and the extensional properties of the resulting dough were assessed with a texture analyzer. Results indicated that, the addition of electrospun fibrils into dough did not improve the generation of elasticity, suggesting that fibrillar morphology is not an essential feature for the generation of elasticity.The effect of extrusion and thermal treatment on zein were tested. The formation of zein large assemblies has been assessed with the use of SDS-PAGE, showing the formation of larger aggregates for either treatment. FTIR and a texture profile analysis were performed to assess the secondary structure and elasticity of zein viscoelastic masses. Results indicated an increased amount of β-sheet structure together with increase of springiness and cohesiveness from 0.56±0.01 and 0.43±0.01 of untreated zein to 0.87±0.01 and 0.77±0.01 of samples treated at 190℃. Treated zein was then added to a dough which was tested for extensional properties with a texture analyzer. Results indicated the generation of strain hardening behavior in dough, a fundamental property for dough gas retention, both in extruded zein and thermally treated samples at 160℃. Finally, extruded zein and thermally treated zein were incorporated into a dough and baked into a loaf of bread. Despite improvement in rheological properties, incorporation into bread did not show improvement in bread quality.The findings of this dissertation showed that the use of zein extrusion and thermal treatment is an effective tool to improve the elasticity and strain hardening behavior of zein dough, potentially finding application as a substitute of gluten. Furthermore, this study showed that it is possible to form a gluten-free dough which is extensible and possess a strain hardening behavior
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
Understanding the basis of the slow starch digestion characteristic of sorghum porridges and how to manipulate starch digestion rate
No full textThe overall goal of this project was to determine the factors causing low starch digestibility or slow starch digestion characteristic of cooked sorghum porridges as opposed to other cereal porridges and their mode of action. First, the roles of major non-starch flour components (protein, fat, dietary fiber) in reduced starch digestibility were investigated by removal of individual components followed by estimation of increase in starch digestibility. All the components contributed somewhat to low starch digestibility, but protein was found to be the single largest contributor. The second study was designed to determine the mode of action by which protein affects starch digestibility. α-Amylase inhibitor assays revealed presence of inhibition activity that diminished with cooking suggesting that the inhibitors are heat-labile and inconsequential to the low digestibility characteristic. Microstructural analysis of flour samples using confocal laser scanning microscopy revealed profound changes in protein microstructure due to cooking. Sorghum proteins formed extended web-like and rigid sheet-like structures that entrapped the starch while maize and rice proteins formed large aggregate structures that seemed to collapse to release gelatinized starch. These results suggest that encapsulation of starch within the sheet-like and web-like structures results in reduced accessibility of starch to degrading enzymes, hence the lower starch digestibility and slow starch digestion characteristic in sorghum porridges. Addition of reducing agent to sorghum during cooking resulted in disruption of the protein structures and increased starch digestibility. These results suggest that the sorghum protein structures formed during cooking are partly due to formation of disulfide bonds, hence the possibility of an oxidizing environment in sorghum flour. To investigate this hypothesis, an oxidizing agent was added to maize and rice flour during cooking. The result was formation of protein structures similar to those observed in cooked sorghum and lower starch digestibility values than those of samples cooked in water. Overall, these studies show that sorghum proteins form resilient web-like and sheet-like structures that interfere with accessibility of gelatinized starch for digestion and that these structures may be as a result of formation of intermolecular disulfide bonds forming large polymeric structures from a potentially oxidizing environment in sorghum
Slowly fermentable dietary fibers for colonic health
No full textDietary fiber refers to a broad class of nutrients that have differing physiological effects; the ideal dietary fiber is likely to: (1) have a low, steady rate of gas production to minimize bloating; (2) produce high levels of short chain fatty acids to prevent the growth of pathogenic bacteria and reduce inflammation; (3) ferment slowly to deliver beneficial fermentation products to all regions of the colon and prevent the production of putrefactive metabolites (e.g., ammonia, phenol); and (4) promote the maintenance of a healthy colonic microbiota by selectively stimulating the growth of beneficial bacteria or preventing the growth of undesirable bacteria. We have undertaken 3 research projects to identify such dietary fibers. First, the fermentation profiles of various dietary fiber fractions from corn, rice, and wheat bran were determined using an in vitro method. An alkali-soluble fraction from corn bran, consisting mainly of arabinoxylans, fermented slowly and produced the highest level of short chain fatty acids. Monosaccharide disappearance data suggested that corn and rice bran arabinoxylans ferment by a debranching mechanism, while wheat bran arabinoxylans contain large unsubstituted xylose regions that are utilized by bacteria first, before fermenting the more difficult to digest highly branched regions. In the second study, starch-entrapped microspheres, composites of starch and alginate, showed potential as a novel source of dietary fiber with slow fermentation characteristics, high butyrate production, and the ability to change the microbiota pattern during in vitro fermentation. The final study compared the fermentation profiles of fecal microbiota obtained from people with inflammatory bowel disease to that of healthy individuals after exposure to starch-entrapped microspheres, waxy corn starch, or fructooligosaccharides. Starch-entrapped microspheres produced more total short chain fatty acids and were more butyrogenic than fructooligosaccharides. Starch-entrapped microspheres were also superior to fructooligosaccharides with respect to preventing the growth of putative undesirable bacteria in inflammatory bowel disease
Starch fragmentation in relation to processing conditions and sensory quality of conventional processed grit corn flakes
No full textA study is presented on the influence of processing conditions on tempering grit rheology and the resulting molecular fragmentation of starch that occurs during the milling of conventional processed grit corn flakes. Corn grits were tempered and milled under a range of combinations of processing conditions which included low and high percent moistures and tempering temperatures. Starch fragmentation was determined using hot and cold water-soluble fractionation methods and an intermediate-pressure size-exclusion chromatograph with multi-angle laser light scattering and refractive index detection. Rheology of the tempered grits was obtained using a broad band frequency squeezing flow technique. Results showed that tempered grit moisture content and tempering temperature and time directly influence the rheology of the tempered corn grits. Rheology of the tempered corn grits was shown to directly influence mill gap width and roll vibrations. Corn grits processed under low moisture-low tempering temperatures were significantly harder. Generally, moisture content was the principal component governing final grit hardness and milled flake thickness in experiments using the same flaking roll setting. Processing conditions resulting in increased shear forces at the flaking mill produced increased amounts of fragmented amylopectin with decreasing average molecular weights. Overall, thinner flakes produced a higher degree of starch fragmentation, yet processing conditions can be modified to yield a range of starch fragmentation for any given milled flake thickness. Characterization of the fragmented starch occurring during milling is presented. Depending on processing conditions, the average molecular weight of the branched polymer was 1.5 × 10 6 to 1.1 × 107 Da. Resulting starch fragmentation was shown to strongly impact bowl life and overall sensory quality of the finished corn flakes. Corn flake samples containing high amounts of starch fragmentation were positively correlated to increased water uptake and increased leaching of starch fragments into water. Processing conditions resulting in corn flakes of the same milled flake thickness, but containing different amounts of starch fragmentation, further corresponded to different bowl lives with the flake sample containing the highest amount of starch fragmentation yielding the poorest bowl life
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