Publications by authors named "Bruce R Hamaker"

149 Publications

Atomistic Modeling of Peptide Aggregation and β-Sheet Structuring in Corn Zein for Viscoelasticity.

Biomacromolecules 2021 Apr 12. Epub 2021 Apr 12.

Whistler Center for Carbohydrate Research, Purdue University, 745 Agricultural Mall Drive, West Lafayette, Indiana 47907, United States.

The structure-function relationships of plant-based proteins that give rise to desirable texture attributes in order to mimic meat products are generally unknown. In particular, it is not clear how to engineer viscoelasticity to impart cohesiveness and proper mouthfeel; however, it is known that intermolecular β-sheet structures have the potential to enhance the viscoelastic property. Here, we investigated the propensity of selected peptide segments within common corn α-zein variants to maintain stable aggregates and β-sheet structures. Simulations on dimer systems showed that stability was influenced by the initial orientation and the presence of contiguous small hydrophobic residues. Simulations using eight-peptide β-sheet oligomers revealed that peptide sequences without proline had higher levels of β-sheet structuring. Additionally, we identified that sequences with a dimer hydrogen-bonding density of >22% tended to have a larger percent β-sheet conformation. These results contribute to understanding how the viscoelasticity of zein can be increased for use in plant-based meat analogues.
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http://dx.doi.org/10.1021/acs.biomac.0c01558DOI Listing
April 2021

Effects of different storage temperatures on the intra- and intermolecular retrogradation and digestibility of sago starch.

Int J Biol Macromol 2021 Apr 5;182:65-71. Epub 2021 Apr 5.

Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, IN 47907, USA. Electronic address:

Three different storage temperatures including room temperature (RT), 4 °C and -20 °C were investigated in this study, with respects to their effects on the retrogradation property and in vitro digestibility of gelatinized sago starch. Storage at -20 °C resulted in the highest amount of both intra- and intermolecular double helices and a fracture-like structure under scanning electron microscopy (SEM). These crystallites were more homogenous while less thermally stable than that from RT and 4 °C storage conditions. Storage at RT significantly increased the stability and heterogeneity of the formed crystallites, resulting in a sponge-like structure under SEM. Causally, the digestion rate of retrograded sago starch by α-amylase was significantly lowered after storage at -20 °C compared to that at RT and 4 °C. The crystallite heterogeneity, thermal stability, and ratio of inter- to intramolecular double helices were possibly the main driven factors for the observed digestion rates instead of the amount and micro-morphology of the crystallites. These results supply potential tools for the manufacture of food products with slower starch digestibility.
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http://dx.doi.org/10.1016/j.ijbiomac.2021.03.195DOI Listing
April 2021

A Unique Gut Microbiome-Physical Function Axis Exists In Older People With HIV: An Exploratory Study.

AIDS Res Hum Retroviruses 2021 Mar 31. Epub 2021 Mar 31.

University of Colorado , Medicine/ID, Mail Stop B168, 12700 E. 19th Ave, Aurora, Colorado, United States, 80045;

Impairments in physical function and increased systemic levels of inflammation have been observed in middle-aged and older persons with HIV (PWH). We previously demonstrated that in older persons, associations between gut microbiota and inflammation differed by HIV serostatus. To determine whether relationships between the gut microbiome and physical function measurements would also be distinct between older persons with and without HIV, we re-analyzed existing gut microbiome and short chain fatty acid (SCFA) data in conjunction with previously collected measurements of physical function and body composition from the same cohorts of older (51-74yrs), non-frail PWH receiving effective antiretroviral therapy (N=14) and age-balanced uninfected controls (N=22). Associations between relative abundance (RA) of the most abundant bacterial taxa or stool SCFA levels with physical function and body composition were tested using HIV-adjusted linear regression models. In older PWH, but not in controls, greater RA of Alistipes, Escherichia, Prevotella, Megasphaera, and Subdoligranulum were associated with reduced lower extremity muscle function, decreased lean mass, or lower Short Physical Performance Battery (SPPB) scores. Conversely, greater RA of Dorea, Coprococcus, and Phascolarctobacterium in older PWH were associated with better muscle function, lean mass, and SPPB scores. Higher levels of the SCFA butyrate associated with increased grip strength in both PWH and controls. Our findings indicate that in older PWH, both negative and positive associations exist between stool microbiota abundance and physical function. Different relationships were observed in older uninfected persons, suggesting features of a unique gut-physical function axis in PWH.
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http://dx.doi.org/10.1089/AID.2020.0283DOI Listing
March 2021

Integrating end-user preferences into breeding programmes for roots, tubers and bananas.

Int J Food Sci Technol 2021 Mar 3;56(3):1071-1075. Epub 2021 Mar 3.

Bill & Melinda Gates Foundation Discovery/Crop R&D Global Growth & Opportunity Agriculture Seattle WA USA.

"" special issue, brings together new knowledge about quality traits required for roots, tubers and bananas (RTB) varieties to successfully meet diverse user preferences and expectations, along the variety development and RTB value chains (production, processing, marketing, food preparation, consumption). Key RTB crops in sub-Saharan Africa are cassava, yams, sweetpotatoes, potatoes and bananas/plantains. They are mainly consumed directly as boiled pieces or pounded in the form of smooth, not sticky, and stretchable dough. They are also stewed, steamed or fried. Cassava, the most widely grown RTB, is generally boiled, stewed or steamed in Eastern and Southern Africa, and in West and Central Africa is usually processed directly into derivative products, e.g. whole root fermentation through retting or heap fermentation; fermentation/dewatering of the mash. Biophysical and social knowledge presented in this issue help elaborate goals for both the processing unit operations (food scientist control) and variety traits (breeder control).
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http://dx.doi.org/10.1111/ijfs.14911DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7986057PMC
March 2021

Heavy metal contamination and health risk assessment in grains and grain-based processed food in Arequipa region of Peru.

Chemosphere 2021 Jan 28;274:129792. Epub 2021 Jan 28.

Whistler Center for Carbohydrate Research and Department of Food Science, Purdue University, West Lafayette, IN, USA. Electronic address:

Heavy metals (HMs) in crops and processed foods are a concern and pose a potential serious health hazard. This study investigated possible presence of HMs in grains and processed products in the Region of Arequipa in Peru. Concentrations of Cd, As, Sn, Pb, and Hg were determined for commonly consumed grains in 18 districts of the region and processed products from 3 popular markets of Arequipa city, using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Cold Vapor Atomic Absorption Spectroscopy (CVAAS). HM concentrations above the Codex General Standard limits were found for As (0.17 mg kg) and Cd (0.11 mg kg) in cereal grains. Elevated Pb concentrations of 0.55, 0.75, and 5.08 mg kg were found for quinoa, maize, and rice products, respectively; and attributed to processing conditions. The Total Hazard Index (HI) for polished rice and rice products had values between 1 and 10, showing non-carcinogenic adverse effects. Total Target Cancer Risk (TR) and uncertainty analysis of percentile P for polished rice and quinoa products gave values above permissible limit of 10, indicating an unacceptable cancer risk. The Nemerow Composite Pollution Index method (NCPI) showed that processed products had a significant pollution level due to the presence of Pb. While most crops grains had acceptable low HM levels, this is the first report of concerning HM concentrations in some consumed grains and processed products in southern Peru and indicates the necessity to find ways to decrease certain toxic metals in foods.
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http://dx.doi.org/10.1016/j.chemosphere.2021.129792DOI Listing
January 2021

High arabinoxylan fine structure specificity to gut bacteria driven by corn genotypes but not environment.

Carbohydr Polym 2021 Apr 16;257:117667. Epub 2021 Jan 16.

Whistler Center for Carbohydrate Research and Department of Food Science, Purdue University, West Lafayette, IN, 47907, USA. Electronic address:

While gut bacteria have different abilities to utilize dietary fibers, the degree of fiber structural alignment to bacteria species is not well understood. Corn bran arabinoxylan (CAX) was used to investigate how minor polymer fine structural differences at the genotype × environment level influences the human gut microbiota. CAXs were extracted from 4 corn genotypes × 3 growing years and used in in vitro fecal fermentations. CAXs from different genotypes had varied contents of arabinose/xylose ratio (0.46-0.54), galactose (58-101 mg/g), glucuronic acid (18-32 mg/g). There was genotype- but not environment-specific differences in fine structures. After 24 h fermentation, CAX showed different acetate (71-86 mM), propionate (35-44 mM), butyrate (7-10 mM), and total short chain fatty acid (SCFA) (117-137 mM) production. SCFA profiles and gut microbiota both shifted in a genotype-specific way. In conclusion, the study reveals a very high specificity of fiber structure to gut bacteria use and SCFA production.
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http://dx.doi.org/10.1016/j.carbpol.2021.117667DOI Listing
April 2021

Structure and binding ability of self-assembled α-lactalbumin protein nanotubular gels.

Biotechnol Prog 2021 Jan 19:e3127. Epub 2021 Jan 19.

Carl E. Haas Endowed Chair in Food Industries, Department of Food Science and Technology, The Ohio State University, Columbus, Ohio, USA.

Partial hydrolysis of whey-based α-lactalbumin (α-La) with Bacillus licheniformis protease (BLP) induces the formation of nanotubular structures in the presence of calcium ions by a self-assembly process. α-La nanotubes (α-LaNTs) exist in the form of regular hollow strands with well-defined average dimensions. The growth of nanotubes induces the formation of stiff transparent protein gels due to the well-arranged networks that the strands can form; these gels can be used for entrapment, transportation, and target delivery of bioactive agents in the industry. High purity of α-La (free of other whey protein fractions) is desirable for nanotube formation; however, pure proteins are very expensive and not practically obtained for industrial applications. Thus, the purpose of this research was to construct α-LaNTs from an α-La preparation with lower purity and to study the gelation phenomena triggered by the self-assembled nanotubes. Some structural features of nanotube gels and their active agent-binding abilities were also investigated. A lower amount of α-LaNTs was observed when low purity α-La was used for nanotube formation. Nanotube growth induced gel formation and higher gel stiffness was obtained when compared to α-La hydrolysates. α-La was denatured after hydrolysis and self-assembly, and remarkable changes were observed in the α-helix and β-sheet domains of α-La structure. Increased intensity in Amide I and II regions indicated potential locations for binding of active agents to α-LaNTs. Whey-based α-La without much purification can be used to produce nanotubular gels and these gels can be considered carrying matrices for active agents in various industrial applications.
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http://dx.doi.org/10.1002/btpr.3127DOI Listing
January 2021

Food Matrix Effects for Modulating Starch Bioavailability.

Annu Rev Food Sci Technol 2021 03 4;12:169-191. Epub 2021 Jan 4.

State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu 214122, China; email:

As the prevalence of obesity and diabetes has continued to increase rapidly in recent years, dietary approaches to regulating glucose homeostasis have gained more attention. Starch is the major source of glucose in the human diet and can have diverse effects, depending on its rate and extent of digestion in the small intestine, on postprandial glycemic response, which over time is associated with blood glucose abnormalities, insulin sensitivity, and even appetitive response and food intake. The classification of starch bioavailability into rapidly digestible starch, slowly digestible starch, and resistant starch highlights the nutritional values of different starches. As starch is the main structure-building macroconstituent of foods, its bioavailability can be manipulated by selection of food matrices with varying degrees of susceptibility to amylolysis and food processing to retain or develop new matrices. In this review, the food factors that may modulate starch bioavailability, with a focus on food matrices, are assessed for a better understanding of their potential contribution to human health. Aspects affecting starch nutritional properties as well as production strategies for healthy foods are also reviewed, e.g., starch characteristics (different type, structure, and modification), food physical properties (food form, viscosity, and integrity), food matrix interactions (lipid, protein, nonstarch polysaccharide, phytochemicals, organic acid, and enzyme inhibitor), and food processing (milling, cooking, and storage).
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http://dx.doi.org/10.1146/annurev-food-070620-013937DOI Listing
March 2021

Some pearl millet-based foods promote satiety or reduce glycaemic response in a crossover trial.

Br J Nutr 2020 Dec 14:1-11. Epub 2020 Dec 14.

Whistler Center for Carbohydrate Research & Department of Food Science, Purdue University, West Lafayette, IN, USA.

In a previous trial in Mali, we showed that traditional pearl millet couscous and thick porridge delayed gastric emptying (about 5 h half-emptying times) in a normal-weight population compared with non-traditional carbohydrate-based foods (pasta, potatoes, white rice; about 3 h half-emptying times), and in a gastric simulator we showed millet couscous had slower digestion than wheat couscous. In light of these findings, we tested the hypothesis in a normal-weight US population (n 14) that millet foods would reduce glycaemic response (continuous glucose monitor), improve appetitive sensations (visual analogue scale ratings), as well as reduce gastric emptying rate (13C-octanoic acid breath test). Five carbohydrate-based foods (millet couscous - commercial and self-made, millet thick porridge, wheat couscous, white rice) were fed in a crossover trial matched on available carbohydrate basis. Significantly lower overall glycaemic response was observed for all millet-based foods and wheat couscous compared with white rice (P ≤ 0·05). Millet couscous (self-made) had significantly higher glycaemic response than millet couscous (commercial) and wheat couscous (P < 0·0001), but as there were no differences in peak glucose values an extended glycaemic response was indicated for self-made couscous. Millet couscous (self-made) had significantly lower hunger ratings and higher fullness ratings (P < 0·05) than white rice, millet thick porridge and millet couscous (commercial). A normal gastric emptying rate (<3 h half-emptying times) was observed for all foods, with no significant differences among them. In conclusion, some traditionally prepared pearl millet foods show the potential to reduce glycaemic response and promote satiety.
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http://dx.doi.org/10.1017/S0007114520005036DOI Listing
December 2020

Investigating the potential of slow-retrograding starches to reduce staling in soft savory bread and sweet cake model systems.

Food Res Int 2020 12 24;138(Pt A):109745. Epub 2020 Sep 24.

Whistler Center for Carbohydrate Research, Purdue University, 745 Agriculture Mall Drive, West Lafayette, IN 47907, USA; Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, IN 47907, USA. Electronic address:

The potential anti-staling property of starches with slow-retrograding amylopectin was studied in soft wheat bread and cake model systems. Normal rice, waxy rice, and wheat starches were processed by drum drying or extrusion, and native starch was used as a comparator. Extrusion processing causing amylopectin fragmentation can reduce intermolecular retrogradation of rice starch. Starches were incorporated into model breads and cakes as partial replacements for flour on a dry weight basis (3 and 6% for cakes, 5 and 15% for breads). Starches pregelatinized by extrusion had moderate molecular fragmentation, as indicated by RVA and HPSEC-MALLS-RI. Starches previously shown to have lower intermolecular retrograding amylopectin (normal rice, waxy rice) resulted in minor to moderate reductions in hardness and other textural properties as indicated by texture profile analysis (TPA) in breads and cakes upon storage for up to 12 wk. A higher degree of starch fragmentation is suggested to produce lower staling. Incorporation of normal and waxy rice starches resulted in softer breads and cakes than wheat starch, which could be attributed to the shorter external and internal amylopectin chains of rice starch. Higher inclusion (15%) of slow-retrograding waxy rice in the bread model system showed the most potential for anti-staling property.
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http://dx.doi.org/10.1016/j.foodres.2020.109745DOI Listing
December 2020

Gut microbiota modulation with long-chain corn bran arabinoxylan in adults with overweight and obesity is linked to an individualized temporal increase in fecal propionate.

Microbiome 2020 08 19;8(1):118. Epub 2020 Aug 19.

Department of Agricultural, Food & Nutritional Science, University of Alberta, Edmonton, AB, T6G 2E1, Canada.

Background: Variability in the health effects of dietary fiber might arise from inter-individual differences in the gut microbiota's ability to ferment these substrates into beneficial metabolites. Our understanding of what drives this individuality is vastly incomplete and will require an ecological perspective as microbiomes function as complex inter-connected communities. Here, we performed a parallel two-arm, exploratory randomized controlled trial in 31 adults with overweight and class-I obesity to characterize the effects of long-chain, complex arabinoxylan (n = 15) at high supplementation doses (female: 25 g/day; male: 35 g/day) on gut microbiota composition and short-chain fatty acid production as compared to microcrystalline cellulose (n = 16, non-fermentable control), and integrated the findings using an ecological framework.

Results: Arabinoxylan resulted in a global shift in fecal bacterial community composition, reduced α-diversity, and the promotion of specific taxa, including operational taxonomic units related to Bifidobacterium longum, Blautia obeum, and Prevotella copri. Arabinoxylan further increased fecal propionate concentrations (p = 0.012, Friedman's test), an effect that showed two distinct groupings of temporal responses in participants. The two groups showed differences in compositional shifts of the microbiota (p ≤ 0.025, PERMANOVA), and multiple linear regression (MLR) analyses revealed that the propionate response was predictable through shifts and, to a lesser degree, baseline composition of the microbiota. Principal components (PCs) derived from community data were better predictors in MLR models as compared to single taxa, indicating that arabinoxylan fermentation is the result of multi-species interactions within microbiomes.

Conclusion: This study showed that long-chain arabinoxylan modulates both microbiota composition and the output of health-relevant SCFAs, providing information for a more targeted application of this fiber. Variation in propionate production was linked to both compositional shifts and baseline composition, with PCs derived from shifts of the global microbial community showing the strongest associations. These findings constitute a proof-of-concept for the merit of an ecological framework that considers features of the wider gut microbial community for the prediction of metabolic outcomes of dietary fiber fermentation. This provides a basis to personalize the use of dietary fiber in nutritional application and to stratify human populations by relevant gut microbiota features to account for the inconsistent health effects in human intervention studies.

Trial Registration: Clinicaltrials.gov, NCT02322112 , registered on July 3, 2015. Video Abstract.
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http://dx.doi.org/10.1186/s40168-020-00887-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7439537PMC
August 2020

Formulation of Orange Juice with Dietary Fibers Enhances Bioaccessibility of Orange Flavonoids in Juice but Limits Their Ability to Inhibit Glucose Transport.

J Agric Food Chem 2020 Sep 24;68(35):9387-9397. Epub 2020 Aug 24.

PepsiCo R&D, Barrington, Illinois 60010, United States.

The effect of formulating orange juice (OJ) with dietary fibers (DFs) on bioaccessibility of flavonoids and their ability to inhibit glucose transport in Caco-2 cells were investigated on Valencia orange fruit (OF), OJ, and OJ formulated with 1 and 2.8% DFs. DFs were either orange pomace (P) or commercial pulverized citrus pulp fiber (CF). Juice extraction and formulation with CF led to minimal loss of flavonoids compared to formulation with P (474 μmol/100 g for OF vs 315-368 μmol/100 g for OJ and OJ with CF, and 266-280 μmol/100 g for OJ with P). Addition of DFs led to similar or improved flavonoid bioaccessibility compared to OJ (9.5% in OJ vs 7.9-33.4% with DFs) but higher glucose transport in Caco-2 cells (0.45 μmol/min in OJ alone vs 0.64-0.94 μmol/min with DFs). This paradoxical effect was attributed to potential complexation of flavonoids and DFs, preventing flavonoids from interfering with glucose transport.
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http://dx.doi.org/10.1021/acs.jafc.0c03334DOI Listing
September 2020

Quantitative approach to study secondary structure of proteins by FT-IR spectroscopy, using a model wheat gluten system.

Int J Biol Macromol 2020 Dec 8;164:2753-2760. Epub 2020 Aug 8.

Whistler Carbohydrate Research Center, Purdue University, 745 Agricultural Mall Drive, West Lafayette, IN 47907, USA; Department of Food Science and Technology, The Ohio State University, 2015 Fyffe Road, Columbus, OH 43210-1007, USA. Electronic address:

Amide I and Amide III vibrational modes are frequently used to study protein secondary structure with Fourier transform infrared (FT-IR) spectroscopy. However, for protein mixtures, neither the sole Amide I nor Amide III region provides sufficient information for structural quantitation because of overlapping peaks, especially in the Amide I region. Here, an improved quantitative approach is proposed to estimate secondary structure of protein systems using resolution enhancement and curve-fitting data processing techniques on a gluten model system to investigate structure-function relationships. Twelve different scenarios were prepared to assign bands in the Amide I region. Frequency ranges of 1660-1640 cm and 1665-1660 cm were found to highly contribute to variability in secondary structure contents of samples. Utilization of the Amide III region as a conducive tool to assign bands in the Amide I region led to a better differentiation of some secondary structural motifs and a more accurate quantitation of protein secondary structure. The study presents an understanding of FT-IR data analysis for a quick technique to assess secondary structures of protein mixtures.
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http://dx.doi.org/10.1016/j.ijbiomac.2020.07.299DOI Listing
December 2020

On the role of the internal chain length distribution of amylopectins during retrogradation: Double helix lateral aggregation and slow digestibility.

Carbohydr Polym 2020 Oct 13;246:116633. Epub 2020 Jun 13.

School of Engineering, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada; Department of Food Science, iFOOD Multidisciplinary Center, Aarhus University, Agro Food Park 48, Aarhus N, 8200, Denmark. Electronic address:

A structure-digestion model is proposed to explain the formation of α-amylase-slowly digestible structures during amylopectin retrogradation. Maize and potato (normal and waxy) and banana starch (normal and purified amylopectin through alcohol precipitation), were analyzed for amylose ratio and size (HPSEC) and amylopectin unit- and internal-chain length distribution (HPAEC). Banana amylopectin (BA), like waxy potato (WP), exhibited a larger number of B3-chains, fewer BS- and B-chains and lower S:L and BS:BL ratios than maize, categorizing BA structurally as type-4. WP exhibited a significantly greater tendency to form double helices (DSC and C-NMR) than BA, which was attributed to its higher internal chain length (ICL) and fewer DP6-12-chains. However, retrograded BA was remarkably more resistant to digestion than WP. Lower number of phosphorylated B-chains, more S- and B-chains and shorter ICL, were suggested to result in α-amylase-slowly digestible structures through further lateral packing of double helices (suggested by thermo-rheology) in type-4 amylopectins.
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http://dx.doi.org/10.1016/j.carbpol.2020.116633DOI Listing
October 2020

Conditioning with slowly digestible starch diets in mice reduces jejunal α-glucosidase activity and glucogenesis from a digestible starch feeding.

Nutrition 2020 10 15;78:110857. Epub 2020 May 15.

Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, IN, United States. Electronic address:

Objectives: Maltase-glucoamylase (Mgam) and sucrase-isomaltase (Si) are mucosal α-glucosidases required for the digestion of starch to glucose. We hypothesized that a dietary approach to reduce Mgam and Si activities can reduce glucose generation and absorption, and improve glucose control.

Methods: Rice starch was entrapped in alginate microspheres to moderate in vitro digestion properties. Three groups of 8-wk old mice (n = 8) were conditioned for 7 d with low C-starch-based materials differing in digestion rates (fast, slow, and slower), and then given a digestible C-labeled cornstarch test feeding to determine its digestion to glucose.

Results: Conditioning of the small intestine with the slowly digestible starches for 7 d reduced jejunal α-glucosidase and sucrase activities, as well as glucose absorption for the slowly digestible starch slower group (P < 0.01). A correlative relationship was found between glucose absorption from a cornstarch test feeding given at d 7 and jejunal α-glucosidase and sucrase activities (R = 0.64; 0.67). However, total prandial glucose levels during the 2-h feeding period did not differ.

Conclusions: Decreased glucogenesis from a digestible starch feeding was found in mice conditioned on slowly digestible starch diets, suggesting that a dietary approach incorporating slowly digestible starches may change α-glucosidase activities to moderate glucose absorption rate.
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http://dx.doi.org/10.1016/j.nut.2020.110857DOI Listing
October 2020

Fecal microbiota responses to rice RS3 are specific to amylose molecular structure.

Carbohydr Polym 2020 Sep 26;243:116475. Epub 2020 May 26.

Whistler Center for Carbohydrate Research and Department of Food Science, Purdue University, West Lafayette, IN, 47907, USA; Institute of Food and Nutraceutical Science, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, 200240, PR China. Electronic address:

Resistant starch type 3 (RS3) benefits colon health, but the molecular structural reasons for this effect are unclear. Five rice starches with varied amylose content (19.1 %-40.6 %) were used to investigate their effect on gut microbiota. Size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis were used to characterize whole starch molecular size distributions and chain length distributions. It was found that RS3 with more chains of degree of polymerization (DP) 36-100 and smaller molecular size can promote the relative abundance of some classes of gut bacteria, while other classes were promoted by RS3 with fewer chains of DP 36-100 and larger molecular size. X-ray diffraction and scanning electron microscopy showed that crystallinity types B or C and differences in physical surface affected the microbiota. This study shows that RS3s with different fine structures are utilized differently by gut microbiota, which may be applied to develop functional foods for gut health.
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http://dx.doi.org/10.1016/j.carbpol.2020.116475DOI Listing
September 2020

Maize Bran Particle Size Governs the Community Composition and Metabolic Output of Human Gut Microbiota in Fermentations.

Front Microbiol 2020 25;11:1009. Epub 2020 May 25.

Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, IN, United States.

Differences in the chemical and physical properties of dietary fibers are increasingly known to exert effects on their fermentation by gut microbiota. Here, we demonstrate that maize bran particle size fractions show metabolic output and microbial community differences similar to those we previously observed for wheat brans. As for wheat brans, maize bran particles varied in starch and protein content and in sugar composition with respect to size. We fermented maize bran particles varying in size with human fecal microbiota as inocula, measuring their metabolic fate [i.e., short-chain fatty acids (SCFAs)] and resulting community structure (via 16S rRNA gene amplicon sequencing). Metabolically, acetate, propionate and butyrate productions were size-dependent. 16S rRNA sequencing revealed that the size-dependent SCFA production was linked to divergent microbial community structures, which exerted effects at fine taxonomic resolution (the genus and species level). These results further suggest that the physical properties of bran particles, such as size, are important variables governing microbial community compositional and metabolic responses.
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http://dx.doi.org/10.3389/fmicb.2020.01009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7261838PMC
May 2020

Discrete Fiber Structures Dictate Human Gut Bacteria Outcomes.

Trends Endocrinol Metab 2020 11 21;31(11):803-805. Epub 2020 May 21.

Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, IN 47906, USA.

Supplementation with resistant starches of different structures led to divergent shifts in key bacterial taxa abundance and distinct butyrate or propionate outcomes. A recent randomized controlled trial (RCT) reported by Deehan et al. showed similar responses within treatment groups and dose-response plateauing at 35 g/d. These results support a proposed alignment of discrete dietary fiber (DF) structures with gut bacteria.
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http://dx.doi.org/10.1016/j.tem.2020.05.002DOI Listing
November 2020

Subtle Variations in Dietary-Fiber Fine Structure Differentially Influence the Composition and Metabolic Function of Gut Microbiota.

mSphere 2020 05 6;5(3). Epub 2020 May 6.

Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, Indiana, USA

The chemical structures of soluble fiber carbohydrates vary from source to source due to numerous possible linkage configurations among monomers. However, it has not been elucidated whether subtle structural variations might impact soluble fiber fermentation by colonic microbiota. In this study, we tested the hypothesis that subtle structural variations in a soluble polysaccharide govern the community structure and metabolic output of fermenting microbiota. We performed fecal fermentation studies using arabinoxylans (AXs) from different classes of wheat (hard red spring [AX], hard red winter [AX], and spring red winter [AX]) with identical initial microbiota. Carbohydrate analyses revealed that AX was characterized by a significantly shorter backbone and increased branching compared with those of the hard varieties. Amplicon sequencing demonstrated that fermentation of AX resulted in a distinct community structure of significantly higher richness and evenness than those of hard-AX-fermenting cultures. AX favored OTUs within , whereas AX and AX favored Accordingly, metabolic output varied between hard and soft varieties; higher propionate production was observed with AX and higher butyrate and acetate with AX and AX This study showed that subtle changes in the structure of a dietary fiber may strongly influence the composition and function of colonic microbiota, further suggesting that physiological functions of dietary fibers are highly structure dependent. Thus, studies focusing on interactions among dietary fiber, gut microbiota, and health outcomes should better characterize the structures of the carbohydrates employed. Diet, especially with respect to consumption of dietary fibers, is well recognized as one of the most important factors shaping the colonic microbiota composition. Accordingly, many studies have been conducted to explore dietary fiber types that could predictably manipulate the colonic microbiota for improved health. However, the majority of these studies underappreciate the vastness of fiber structures in terms of their microbial utilization and omit detailed carbohydrate structural analysis. In some cases, this causes conflicting results to arise between studies using (theoretically) the same fibers. In this investigation, by performing fecal fermentation studies using bran arabinoxylans obtained from different classes of wheat, we showed that even subtle changes in the structure of a dietary fiber result in divergent microbial communities and metabolic outputs. This underscores the need for much higher structural resolution in studies investigating interactions of dietary fibers with gut microbiota, both and .
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http://dx.doi.org/10.1128/mSphere.00180-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7203452PMC
May 2020

Corn zein undergoes conformational changes to higher β-sheet content during its self-assembly in an increasingly hydrophilic solvent.

Int J Biol Macromol 2020 Aug 25;157:232-239. Epub 2020 Apr 25.

Whistler Center for Carbohydrate Research, Purdue University, 745 Agricultural Mall Drive, West Lafayette, IN 47907, USA; Department of Food Science, Purdue University, 745 Agricultural Mall Drive, West Lafayette, IN 47907, USA. Electronic address:

Viscoelasticity of corn zein is associated with the formation of β-sheet secondary structures; however, studies of the fundamentals of this conformational change are limited due to zein insolubility and poor analytical resolution. Here, changes in soluble zein conformation were evaluated as the protein self-assembles in increasingly hydrophilic solvents to the concentration just before aggregation and precipitation. Circular dichroism spectra of zein showed that α-helix structures decrease in favor of random coil and β-sheets with increases in water content in an ethanol-water system, similar to observations of zein when it becomes viscoelastic in dough systems. This was further supported by changes in Thioflavin T fluorescence emission spectra and intrinsic viscosity measurements. Two widely recognized molecular models for α-zein (hairpin and superhelical conformations) were tested at 75 and 45% ethanol concentration using molecular dynamics simulation for agreement with experimental results. Increase in solvent hydrophilicity increased β-sheets and reduced distance between backbone anomeric carbons only for hairpin model, suggesting it to be the more valid of the two. These findings emphasize the importance of transformation to β-sheets during zein self-assembly and provide further insight into the mechanisms by which the protein is functionalized into viscoelastic systems.
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http://dx.doi.org/10.1016/j.ijbiomac.2020.04.169DOI Listing
August 2020

African fruit pulp (baobab) modifies provitamin A carotenoid bioaccessibility from composite pearl millet porridges.

J Food Sci Technol 2020 Apr 22;57(4):1382-1392. Epub 2019 Nov 22.

2Department of Food, Bioprocessing and Nutrition Science, Plants for Human Health Institute, North Carolina State University, Kannapolis, NC USA.

Food-to-food fortification of staple cereal products using nutrient-dense plants shows promise to address multiple micronutrient deficiencies including vitamin A, iron and zinc in Sub-Saharan Africa. However, there is limited information on the potential interaction effects that such food-to-food fortified strategies may have on individual micronutrient bioavailability. The main objective of the current study was to investigate the impact of incorporating (baobab fruit pulp), a mineral-rich plant material, on the delivery of carotenoids from a composite cereal porridge. Formulations of native fruit/vegetable-cereal composites were screened for interactions which could influence both bioaccessibility and subsequent intestinal uptake of provitamin A carotenoids. Proportions of pearl millet flour and plant materials were dry blended to provide composite cereal porridges with total provitamin A carotenoid concentrations ranging from 3590.7 ± 23.4 to 3698.5 ± 26.5 μg/100 g (fw) and baobab concentrations ranging from 0 to 25% (dw).While there were no significant differences in provitamin A carotenoid bioaccessibility from porridge formulations containing 5 or 15% baobab, inclusion of 25% baobab resulted in a significant ( < 0.05) decrease in bioaccessibility (13.3%) as compared to the control (23.8%). Despite the reduced bioaccessibility, 6 h uptake efficiency of provitamin A carotenoids by Caco-2 human intestinal cells was not significantly altered by 25% baobab inclusion. These findings suggest that the inhibitory effects on carotenoid micellarization (bioaccessibility) observed with increased baobab addition may not ultimately limit the bioavailability of carotenoids.
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http://dx.doi.org/10.1007/s13197-019-04173-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7054500PMC
April 2020

Consumer Acceptance and Willingness to Pay for Instant Cereal Products With Food-to-Food Fortification in Eldoret, Kenya.

Food Nutr Bull 2020 06 16;41(2):224-243. Epub 2020 Mar 16.

International Maize and Wheat Improvement Centre (CIMMYT), Nairobi, Kenya.

Background: Maize is the major food staple in East and Southern Africa, where food-processing industries are emerging fast. New low-cost extrusion cookers allow small enterprises to enter the market for processed cereals, including instant, fortified, and flavored products.

Objective: Assess consumers' interest and preferences for the new products.

Methods: Consumers (n = 220) in Eldoret, Kenya, were invited to evaluate 4 new cereal products: (1) sifted maize flour mixed with sorghum, (2) instant sifted mixed flour, (3) instant whole flour, and (4) instant whole flour fortified with natural ingredients and to compare them to conventional sifted maize flour, using 2 preparations: stiff porridge () and soft porridge (). These were followed by economic experiments to estimate consumers' willingness to pay (WTP) for the new products and traits.

Results: For , consumers preferred conventional sifted maize flour, while for , they appreciated the new products, especially sifted mixed flour (with sorghum) and instant whole mixed flour. Fortification with food-to-food sources was not appreciated, especially for . Comparing WTP for the traits with their production cost showed that mixed, whole, and instant flours were economical, but not fortification. Maize/sorghum mixtures realized a benefit of 24% over conventional maize flour, whole meal 11%, and instant mixtures 5%.

Conclusions: There is a potential market for improved cereal products in Kenya, but more for than for , especially with instant, mixed, and whole flour. Acceptable and affordable products, fortified with other foods that are locally available, however, still need to be developed, especially for .
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http://dx.doi.org/10.1177/0379572119876848DOI Listing
June 2020

Stored Gelatinized Waxy Potato Starch Forms a Strong Retrograded Gel at Low pH with the Formation of Intermolecular Double Helices.

J Agric Food Chem 2020 Apr 19;68(13):4036-4041. Epub 2020 Mar 19.

Whistler Center for Carbohydrate Research, Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana 47906, United States.

Waxy potato amylopectin has longer internal and external linear chains than rice or corn amylopectin that are capable of retrograding to a higher degree, but its molecular recrystallization is impeded by unprotonated phosphate groups. Here, we studied whether retrogradation and gel properties of waxy potato starch can be enhanced by lowering pH. The gel strength of waxy potato starch was strongly inversely correlated with pH, going from 10 to 4, and its magnitude was higher at pH values in which the ζ potential of the system was low. Waxy potato starch formed a strong aggregate gel driven by the formation of intermolecular double helices (' drop ≈ 1358 Pa, melting Δ = 9.5 J/g) when conditions that reduce electrostatic repulsion (pH 4, ζ = -1.7) are used, a phenomenon that was not observed in low-phosphorylated waxy cereal starches (i.e., waxy rice and corn).
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http://dx.doi.org/10.1021/acs.jafc.9b08268DOI Listing
April 2020

Carbohydrates designed with different digestion rates modulate gastric emptying response in rats.

Int J Food Sci Nutr 2020 Nov 11;71(7):839-844. Epub 2020 Mar 11.

Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, IN, USA.

We sought to determine whether design of carbohydrate-based microspheres to have different digestion rates, while retaining the same material properties, could modulate gastric emptying through the ileal brake. Microspheres made to have three slow digestion rates and a rapidly digested starch analogue (maltodextrin) were administrated to rats by gavage and starch contents in the stomach, proximal and distal small intestine, and caecum were measured 2 h post-gavage. A stepwise increase in the amount of starch retained in the stomach was found for microspheres with incrementally slower rates of digestion. Postprandial glycaemic and insulinaemic responses were incrementally lower for the different microspheres than for the rapidly digestible control. A second-meal effect was observed for slowly digestible starch (SDS) microspheres compared to glucose. Thus, dietary slowly digestible carbohydrates were designed to elicit incremental significant changes in gastric emptying, glycaemic and insulinaemic responses, and they may be a means to trigger the ileal brake.
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http://dx.doi.org/10.1080/09637486.2020.1738355DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7895304PMC
November 2020

Long-term low shear-induced highly viscous waxy potato starch gel formed through intermolecular double helices.

Carbohydr Polym 2020 Mar 31;232:115815. Epub 2019 Dec 31.

Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, IN 47907, USA. Electronic address:

We previously reported that waxy potato and corn starch amylopectin pastes undergo a shear-thickening behavior that occurs at a low shear rate range of 5 to 25 s, and that the effect did not occur for waxy rice starch. Here, we show that the same gelatinized potato amylopectin subjected to a prolonged shear rate of 20 s for 24 h at 5 °C forms a highly viscous gel having a 4-fold higher number of double helices than without shear. Shear-induced starch retrograded aggregates began forming within 20 min of treatment. Amylopectin double helices melted between 40-75 °C resulting in a steep decrease in the storage modulus, indicating that gel formation was caused by intermolecular double helices. Thus, a new phenomenon is reported whereby a waxy potato amylopectin paste, in the presence of long-term low shear, forms double-helical aggregated structures that considerably affects the material's rheological properties.
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http://dx.doi.org/10.1016/j.carbpol.2019.115815DOI Listing
March 2020

A Ribose-Scavenging System Confers Colonization Fitness on the Human Gut Symbiont Bacteroides thetaiotaomicron in a Diet-Specific Manner.

Cell Host Microbe 2020 01 31;27(1):79-92.e9. Epub 2019 Dec 31.

Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA. Electronic address:

Efficient nutrient acquisition in the human gut is essential for microbial persistence. Although polysaccharides have been well-studied nutrients for the gut microbiome, other resources such as nucleic acids and nucleosides are less studied. We describe several ribose-utilization systems (RUSs) that are broadly represented in Bacteroidetes and appear to have diversified to access ribose from a variety of substrates. One Bacteroides thetaiotaomicron RUS variant is critical for competitive gut colonization in a diet-specific fashion. We used molecular genetics to probe the required functions of the system and the nature of the nutrient source(s) underlying this phenotype. Two RUS-encoded ribokinases were the only components required for this effect, presumably because they generate ribose-phosphate derivatives from products of an unlinked but essential nucleoside phosphorylase. Our results underscore the extensive mechanisms that gut symbionts have evolved to access nutrients and the potential for unexpected dependencies among systems that mediate colonization and persistence.
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http://dx.doi.org/10.1016/j.chom.2019.11.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7031954PMC
January 2020

Pearl millet (Pennisetum glaucum) couscous breaks down faster than wheat couscous in the Human Gastric Simulator, though has slower starch hydrolysis.

Food Funct 2020 Jan;11(1):111-122

Whistler Center for Carbohydrate Research & Department of Food Science, Purdue University, West Lafayette, USA.

Consumption of traditional West African pearl millet (Pennisetum glaucum) couscous delayed gastric emptying in our recent human study compared to other starch-based foods (white rice, boiled potatoes, pasta). The objective of this study was to determine whether physical properties of pearl millet couscous affect particle breakdown and starch hydrolysis during simulated gastric digestion to understand the basis of the slow gastric emptying. Starch fine structure and viscosity were analyzed for initial millet and wheat couscous samples by high performance size-exclusion chromatography and the Rapid Visco Analyzer, respectively. Couscous samples were subjected to simulated gastric digestion using the Human Gastric Simulator (HGS), a dynamic model of human gastric digestion. Digesta was collected from the HGS at 30 min intervals over 180 min. Particle size and percent starch hydrolysis of couscous in the digesta were evaluated at each time point. The number of particles per gram of dry mass substantially increased over digestion time for millet couscous (p < 0.05), while changed little for the wheat couscous samples. Millet couscous showed lower starch hydrolysis per unit surface area of particles than wheat couscous (p < 0.05). Slower starch hydrolysis was associated with smaller (p < 0.05) amylose chain length for millet (839-963 DP) than for wheat (1225-1563 DP), which may enable enable a denser packing of millet starch molecules that impedes hydrolysis. We hypothesize that the slow gastric emptying rate of millet couscous observed in humans may be explained by its slow starch hydrolysis property that could activate the ileal brake system, independent of high particle breakdown rate in the stomach.
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http://dx.doi.org/10.1039/c9fo01461fDOI Listing
January 2020

Phenolic compounds are less degraded in presence of starch than in presence of proteins through processing in model porridges.

Food Chem 2020 Mar 23;309:125769. Epub 2019 Oct 23.

Department of Food Science, Purdue University, West Lafayette, IN, United States; Whistler Center for Carbohydrate Research, Purdue University, West Lafayette, IN, United States; School of Chemistry and Biomolecular Sciences, Faculty of Sciences, University of Ottawa, Canada; School of Nutrition Sciences, Faculty of Health Sciences, University of Ottawa, Canada. Electronic address:

Phenolic compounds are known to bind non-covalently with starch, but the impact of this interaction on the stability of the phenolic compounds through processing and digestion has received little attention. In this study, we examined the recovery of intact phenolic compounds (gallic acid-GA, catechin-CAT and epigallocatechin gallate-EGCG) from processed and digested porridges with different formulations (starch or starch/protein). We observed that phenolics were less degraded in presence of starch only than in presence of starch + proteins. This protection seemed to be linked to the ability of the phenolic compounds to form V-type inclusion complexes with starch, with GA, CAT and EGCG in decreasing order of protection. This work could influence formulation of functional cereal-based foods containing phenolic compounds in order to maximize their retention.
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http://dx.doi.org/10.1016/j.foodchem.2019.125769DOI Listing
March 2020

Abnormal Eating Patterns Cause Circadian Disruption and Promote Alcohol-Associated Colon Carcinogenesis.

Cell Mol Gastroenterol Hepatol 2020 2;9(2):219-237. Epub 2019 Nov 2.

Department of Immunology, Mayo Clinic, Rochester, Minnesota. Electronic address:

Background & Aims: Alcohol intake with circadian rhythm disruption (CRD) increases colon cancer risk. We hypothesized that eating during or around physiologic rest time, a common habit in modern society, causes CRD and investigated the mechanisms by which it promotes alcohol-associated colon carcinogenesis.

Methods: The effect of feeding time on CRD was assessed using B6 mice expressing a fusion protein of PERIOD2 and LUCIFERASE (PER2::LUC) were used to model colon polyposis and to assess the effects of feeding schedules, alcohol consumption, and prebiotic treatment on microbiota composition, short-chain fatty acid levels, colon inflammation, and cancer risk. The relationship between butyrate signaling and a proinflammatory profile was assessed by inactivating the butyrate receptor GPR109A.

Results: Eating at rest (wrong-time eating [WTE]) shifted the phase of the colon rhythm in PER2::LUC mice. In TS4Cre × APC mice, a combination of WTE and alcohol exposure (WTE + alcohol) decreased the levels of short-chain fatty acid-producing bacteria and of butyrate, reduced colonic densities of regulatory T cells, induced a proinflammatory profile characterized by hyperpermeability and an increased mucosal T-helper cell 17/regulatory T cell ratio, and promoted colorectal cancer. Prebiotic treatment improved the mucosal inflammatory profile and attenuated inflammation and cancer. WTE + alcohol-induced polyposis was associated with increased signal transducer and activator of transcription 3 expression. Decreased butyrate signaling activated the epithelial signal transducer and activator of transcription 3 in vitro. The relationship between butyrate signaling and a proinflammatory profile was confirmed in human colorectal cancers using The Cancer Genome Atlas.

Conclusions: Abnormal timing of food intake caused CRD and interacts with alcohol consumption to promote colon carcinogenesis by inducing a protumorigenic inflammatory profile driven by changes in the colon microbiota and butyrate signaling. Accession number of repository for microbiota sequence data: raw FASTQ data were deposited in the NCBI Sequence Read Archive under project PRJNA523141.
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http://dx.doi.org/10.1016/j.jcmgh.2019.10.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6957855PMC
November 2019