Publications by authors named "Barbara A Williams"

40 Publications

Interplay between grain digestion and fibre in relation to gastro-small-intestinal passage rate and feed intake in pigs.

Eur J Nutr 2021 May 5. Epub 2021 May 5.

Australian Research Council, Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, Australia.

Purpose: The combined effects of grain digestibility and dietary fibre on digesta passage rate and satiety in humans are poorly understood. Satiety can be increased through gastric distention, reduced gastric emptying rate and when partially digested nutrients reach the terminal ileum to stimulate peptide release through the ileal/colonic brakes to slow the rate of digesta passage. This study determined the effects of grain digestibility and insoluble fibre on mean retention time (MRT) of digesta from mouth-to-ileum, feed intake (FI), starch digestion to the terminal ileum and faecal short chain fatty acids (SCFA) in a pig model.

Method: Twelve grain-based [milled sorghum (MS), steam-flaked-sorghum, milled wheat, and steam-flaked-wheat (SFW)] diets with different intrinsic rates of starch digestion, assessed by apparent amylase diffusion coefficient (ADC), and fibre from oat hulls (OH) at 0, 5 and 20% of the diet were fed to ileal-cannulated pigs.

Result: MRT was affected by grain-type/processing (P < 0.05) and fibre amount (P < 0.05). An approximate tenfold increase in ADC showed a limited decline in MRT (P = 0.18). OH at 20% increased MRT (P < 0.05) and reduced FI (P < 0.05). Ileal digestibility of starch increased and faecal SCFA concentration decreased with ADC; values for MS being lower (P < 0.001) and higher (P < 0.05), respectively, than for SFW.

Conclusions: Lower ileal digestibility of starch, higher faecal SCFA concentration and longer MRT of MS than SFW, suggest the ileal/colonic brakes may be operating. FI appeared to decrease with increasing MRT. MRT increased and intake decreased with grain-based foods/feeds that have low starch digestibility and substantial amounts of insoluble fibre.
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http://dx.doi.org/10.1007/s00394-021-02567-3DOI Listing
May 2021

An Illustrative Analysis of Atypical Gas Production Profiles Obtained from In Vitro Digestibility Studies Using Fecal Inoculum.

Animals (Basel) 2021 Apr 9;11(4). Epub 2021 Apr 9.

Department of Animal BioSci.s, University of Guelph, Guelph, ON N1G 2W1, Canada.

Gas production profiles typically show a monotonically increasing monophasic pattern. However, atypical gas production profiles exist whereby at least two consecutive phases of gas production or additional extraneous features that distort the typical profile are present. Such profiles are more likely to occur with the use of a fecal inoculum and are much less well described. The presence of multiple phases or non-descript extraneous features makes it difficult to apply directly recommended modeling approaches such as standard response functions or classical growth functions. To overcome such difficulties, extensions of the Mitscherlich equation and a numerical modeling option also based on the Mitscherlich are explored. The numerical modeling option uses an estimate of relative rate obtained from the smoothed data profile and an estimate of maximum gas produced together with any lag time information drawn from the raw data to construct a simple Mitscherlich equation. In summary, this article illustrates the analysis of atypical gas production profiles obtained using a fecal inoculum and explores the methodology of numerical modeling to reconstruct equivalent typical growth-like trends.
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http://dx.doi.org/10.3390/ani11041069DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8069660PMC
April 2021

Interaction of cellulose and xyloglucan influences in vitro fermentation outcomes.

Carbohydr Polym 2021 Apr 27;258:117698. Epub 2021 Jan 27.

Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD, 4072, Australia. Electronic address:

To investigate the effects of interactions between cellulose and xyloglucan (XG) on in vitro fermentation, a composite of bacterial cellulose (BC) incorporating XG during pellicle formation (BCXG), was fermented using a human faecal inoculum, and compared with BC, XG and a mixture (BC&XG) physically blended to have the same BC to XG ratio of BCXG. Compared to individual polysaccharides, the fermentation extent of BC and fermentation rate of XG were promoted in BC&XG. XG embedded in the BCXG composite was degraded less than in BC&XG, while more cellulose in BCXG was fermented than in BC&XG. This combination explains the similar amount of short chain fatty acid production noted throughout the fermentation process for BCXG and BC&XG. Microbial community dynamics for each substrate were consistent with the corresponding polysaccharide degradation. Thus, interactions between cellulose and XG are shown to influence their fermentability in multiple ways.
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http://dx.doi.org/10.1016/j.carbpol.2021.117698DOI Listing
April 2021

Wheat cell walls and constituent polysaccharides induce similar microbiota profiles upon fermentation despite different short chain fatty acid end-product levels.

Food Funct 2021 Feb;12(3):1135-1146

Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072, Australia.

Plant cell walls as well as their component polysaccharides in foods can be utilized to alter and maintain a beneficial human gut microbiota, but it is not known whether the architecture of the cell wall influences the gut microbiota population. In this study, wheat flour cell walls (WCW) were isolated and compared with their major constituents - arabinoxylan (AX), mixed linkage (1,3)(1,4)-β-glucan (MLG) and cellulose - both separately and as a physical mixture of polysaccharides (Mix) equivalent in composition to WCW. These samples underwent in vitro fermentation with a faecal inoculum from pigs fed a diet free of cereals and soluble-fibre to avoid prior adaptation to substrates. During fermentation, samples were collected for DNA extraction and 16S rRNA gene amplicon sequencing. Bioinformatics analyses revealed that the microbial communities promoted during fermentation by AX, MLG, Mix and WCW were similar at the genus level, but differed from the microbiota observed for the cellulose substrate. Differences in proportions of propionate and butyrate end-products were associated with differences in the relative levels of genera. These findings show that, in this experiment, the microbes that flourished were able to utilize diverse WCW polysaccharides alone, in mixtures or in intact cell walls in a similar way, but that different fermentation end-products were associated with AX (propionate) or MLG (butyrate) polysaccharides.
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http://dx.doi.org/10.1039/d0fo02509gDOI Listing
February 2021

Metabolism of Black Carrot Polyphenols during In Vitro Fermentation is Not Affected by Cellulose or Cell Wall Association.

Foods 2020 Dec 21;9(12). Epub 2020 Dec 21.

Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland-St. Lucia Campus, Brisbane, QLD 4072, Australia.

Fruit and vegetable polyphenols are associated with health benefits, and those not absorbed could be fermented by the gastro-intestinal tract microbiota. Many fermentation studies focus on "pure" polyphenols, rather than those associated with plant cell walls (PCW). Black carrots (BlkC), are an ideal model plant food as their polyphenols bind to PCW with minimal release after gastro-intestinal digestion. BlkC were fractionated into three components-supernatant, pellet after centrifugation, and whole puree. Bacterial cellulose (BCell) was soaked in supernatant (BCell&S) as a model substrate. All substrates were fermented in vitro with a pig faecal inoculum. Gas kinetics, short chain fatty acids, and ammonium production, and changes in anthocyanins and phenolic acids were compared. This study showed that metabolism of BlkC polyphenols during in vitro fermentation was not affected by cellulose/cell wall association. In addition, BCell&S is an appropriate model to represent BlkC fermentation, suggesting the potential to examine fermentability of PCW-associated polyphenols in other fruits/vegetables.
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http://dx.doi.org/10.3390/foods9121911DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7766557PMC
December 2020

fermentation outcomes of arabinoxylan and galactoxyloglucan depend on fecal inoculum more than substrate chemistry.

Food Funct 2020 Sep;11(9):7892-7904

Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, 4072, Australia.

Using in vitro fermentation conditions, this study investigated the fermentation characteristics of arabinoxylan (AX) and xyloglucan (XG) with a fecal inoculum that was collected either from humans consuming unrestricted diets or pigs fed a semi-defined diet with cellulose being the sole non-starch polysaccharide for 10 days prior to fecal collection. Metagenomic analysis revealed that microbial communities in the two types of inoculum were distinctively different, which led to distinct fermentation characteristics with the polysaccharides. The microbial communities fermented with the porcine fecal inoculum were clustered according to the fermentation time, while those fermented with the human fecal inoculum were differentiated by the substrates. Using the porcine fecal inoculum, irrespective of the substrates, Prevotella copri and the unclassified lineage rc4-4 were the dominant operational taxonomic units (OTUs) promoted during fermentation. Fermentation of wheat AX (WAX) and galacto-XG (GXG) with the human fecal inoculum, however, promoted different OTUs, except for a shared OTU belonging to Lachnospiraceae. Specifically, WAX promoted the growth of Bacteroides plebeius and a Blautia sp., while GXG promoted an unclassified Bacteroidales, Parabacteroides distasonis, Bacteroides uniformis and Bacteroides sp. 2. These changes in bacterial communities were in accordance with the short chain fatty acid (SCFA) production, where comparable SCFA profiles were obtained from the porcine fecal fermentation while different amounts and proportions of SCFA were acquired from fermentation of WAX and GXG with the human fecal inoculum. Altogether, this study indicated that the starting inoculum composition had a greater effect than polysaccharide chemistry in driving fermentation outcomes.
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http://dx.doi.org/10.1039/d0fo01103gDOI Listing
September 2020

High amylose wheat starch structures display unique fermentability characteristics, microbial community shifts and enzyme degradation profiles.

Food Funct 2020 Jun;11(6):5635-5646

Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, Brisbane, Australia.

A slower rate of starch digestion in the small intestine increases the amount of resistant starch (RS) entering the large intestine, which is associated with health benefits. Although increasing the amylose (AM) content of dietary starch intake is one way to increase RS, the processes involved in gut microbial hydrolysis and fermentation of high AM-RS substrates are poorly understood. In this study, five high AM wheat (HAW) starches ranging from 47% AM to 93% AM and a wild type (37% AM), in both native granular and cooked forms, were subjected to in vitro fermentation with a porcine faecal inoculum. Fermentation kinetics, temporal microbial changes, amylolytic enzyme activities and residual starch were determined. All granular starches showed similar fermentation characteristics, independent of AM level, whereas cooking accelerated fermentation of lower AM but slowed fermentation of high AM starches. HAW starches with a very high AM content (>85%) all had similar fermentation kinetics and short-chain fatty acid end-product profiles. Microbial α-amylase, β-amylase, pullulanase and amyloglucosidase enzymatic activities were all detected and followed fermentation kinetics. HAW starch promoted shifts in the microbial community, with increases of the family Lachnospiraceae and the genus Treponema observed, while the genera Prevotella and Streptococcus were reduced in comparison to 37% AM. Overall, these findings suggest that any HAW starch incorporated into high RS food products would be expected to have beneficial microbiota-mediated effects in terms of fermentation kinetics and end products.
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http://dx.doi.org/10.1039/d0fo00198hDOI Listing
June 2020

Purified plant cell walls with adsorbed polyphenols alter porcine faecal bacterial communities during in vitro fermentation.

Food Funct 2020 Jan;11(1):834-845

Centre of Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD 4072, Australia.

A substantial fraction of ingested polyphenols accumulate in the large intestine (LI), attached to undigested plant cell walls (PCW) (dietary fibre). Yet, whether these PCW-bound polyphenols alter the structure and function of the resident microbiota remains unclear. This study characterised bacterial populations during the in vitro fermentation of three standard polyphenols: ferulic acid (FER), (±)-catechin (CAT), and cyanidin-3-glucoside (CYAN), adsorbed individually or in combination to apple cell walls (ACW). During fermentation with porcine faeces, samples were collected at regular time-points (up to 72 hours) for bacterial 16S rRNA gene amplicon sequencing and fermentation end-product analyses (short-chain fatty acids and ammonium). The metabolic end-products differed to only a small extent between substrates, though significantly for propionate (P < 0.0001). Significant differences in microbial populations were noted between substrates tested (P < 0.0001). The presence of cyanidin-3-glucoside resulted in the most significant differences between bacterial communities during fermentation of the ACW substrate. Key microbes identified to be associated with the ACW with adsorbed polyphenols as well as individual polyphenols were: Phascolarctobacterium with ACW + FER and FER, the Lachnospiraceae family with ACW + CYAN, Parabacteroides with ACW + CYAN and CYAN, Collinsella and Coprococcus with ACW + CAT, and the Clostridiales order with ACW + CAT and CAT. This study has demonstrated the use of a simplified model to indicate any microbial effects of polyphenols associated with dietary fibre in whole fruits. This work has shown that individual polyphenols, or those adsorbed to PCW, have potentially very different effects on the gut bacteria. Future work could examine further polyphenols associated with a range of fresh fruits.
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http://dx.doi.org/10.1039/c9fo02428jDOI Listing
January 2020

Wheat bran and oat hulls have dose-dependent effects on ad-libitum feed intake in pigs related to digesta hydration and colonic fermentation.

Food Funct 2019 Dec;10(12):8298-8308

Australian Research Council, Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, 4072, Australia.

Undigested nutrients and fermentable fibre in the distal ileum and colon stimulate intestinal brakes, which reduce gastric-emptying and digesta-passage-rate, and subsequently limit feed/food-intake. Fibre can also stimulate passage rate potentially increasing feed intake (FI). In order to experimentally determine the relationships between these two hypothesised actions of fibre, five levels of wheat-bran (WB) or oat-hulls (OH) were added to a highly digestible starch-based diet fed to pigs ad-libitum for three weeks. Average-daily-feed-intake (ADFI), faecal short-chain-fatty-acids (SCFA) and related parameters were determined at 7, 14 and 21d. A linear mixed model was fitted to FI and fermentation parameters. Overall, WB diets showed 8-11% lower ADFI (7-14d: p < 0.05; 7-21 & 0-21d: p = 0.053) than OH diets. WB diets produced over 20% more (21d: p < 0.01) SCFA than OH or Control diets. WB at 25% produced 22% more (7d: p < 0.05) SCFA than any other diet. Diets with WB at 25 and 35%, showed higher hydration capacity than any other diet (p < 0.001). OH at 10% had an unusually low FI and a markedly higher hydration capacity. With increasing levels of OH, intake of base diet was 7% more than control at 5% OH, but 8% less than control at 20% OH. With increasing WB content, intake of base diet decreased. From these results, we propose that three mechanisms control the effects of fibre on FI: initial increase in passage rate and feed intake at low concentrations of non-swelling fibres; a depression in FI from high fibre bulk; and reduced feed intake from stimulation of ileal and colonic brakes.
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http://dx.doi.org/10.1039/c8fo02496kDOI Listing
December 2019

"Dietary fibre": moving beyond the "soluble/insoluble" classification for monogastric nutrition, with an emphasis on humans and pigs.

J Anim Sci Biotechnol 2019 24;10:45. Epub 2019 May 24.

The University of Queensland, QAAFI Centre for Nutrition and Food Sciences, St. Lucia campus, Brisbane, Qld 4070 Australia.

This review describes dietary fibres originating from a range of foods, particularly in relation to their plant cell walls. It explores the categorization of dietary fibres into "soluble" or "insoluble". It also emphasizes dietary fibre fermentability, in terms of describing how the gastro-intestinal tract (GIT) microbiota respond to a selection of fibres from these categories. Food is categorized into cereals, legumes, fruits and vegetables. Mention is also made of example whole foods and why differences in physico-chemical characteristics between "purified" and "non-purified" food components are important in terms of health. Lastly, recommendations are made as to how dietary fibre could be classified differently, in relation to its functionality in terms of fermentability, rather than only its solubility.
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http://dx.doi.org/10.1186/s40104-019-0350-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6537190PMC
May 2019

Extracellular depolymerisation triggers fermentation of tamarind xyloglucan and wheat arabinoxylan by a porcine faecal inoculum.

Carbohydr Polym 2018 Dec 24;201:575-582. Epub 2018 Aug 24.

ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD, 4072, Australia. Electronic address:

Arabinoxylan (AX) and xyloglucan (XG) are important components of primary cell walls of cereal grains and vegetables/fruits, respectively. Despite the established health benefits of these non-starch polysaccharides, the mechanisms of their utilisation by the gut microbiota are poorly understood. In this study, the mechanisms of solubilised wheat AX and tamarind XG degradation were investigated under in vitro fermentation conditions using a porcine faecal inoculum. Through structural analysis of the polymers, we demonstrate that depolymerisation by microbial surface accessible endo-degrading enzymes occurs prior to active fermentation of AX or XG. Breakdown products are released into the medium and potentially utilised cooperatively by other microbes. Acetate and propionate are the main fermentation products and are produced concurrently with polysaccharide depletion. Butyrate, however, is produced more slowly consistent with it being a secondary metabolite.
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http://dx.doi.org/10.1016/j.carbpol.2018.08.089DOI Listing
December 2018

Food Starch Structure Impacts Gut Microbiome Composition.

mSphere 2018 May-Jun;3(3). Epub 2018 May 16.

Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, Queensland, Australia

Starch is a major source of energy in the human diet and is consumed in diverse forms. Resistant starch (RS) escapes small intestinal digestion and is fermented in the colon by the resident microbiota, with beneficial impacts on colonic function and host health, but the impacts of the micro- and nanoscale structure of different physical forms of food starch on the broader microbial community have not been described previously. Here, we use a porcine fermentation model to establish that starch structure dramatically impacts microbiome composition, including the key amylolytic species, and markedly alters both digestion kinetics and fermentation outcomes. We show that three characteristic food forms of starch that survive digestion in the small intestine each give rise to substantial and distinct changes in the microbiome and in fermentation products. Our results highlight the complexity of starch fermentation processes and indicate that not all forms of RS in foods are degraded or fermented in the same way. This work points the way for the design of RS with tailored degradation by defined microbial communities, informed by an understanding of how substrate structure influences the gut microbiome, to improve nutritive value and/or health benefits. Dietary starch is a major component in the human diet. A proportion of the starch in our diet escapes digestion in the small intestine and is fermented in the colon. In this study, we use a model of the colon, seeded with porcine feces, in which we investigate the fermentation of a variety of starches with structures typical of those found in foods. We show that the microbial community changes over time in our model colon are highly dependent on the structure of the substrate and how accessible the starch is to colonic microbes. These findings have important implications for how we classify starches reaching the colon and for the design of foods with improved nutritional properties.
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http://dx.doi.org/10.1128/mSphere.00086-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5956147PMC
October 2018

Mechanisms of utilisation of arabinoxylans by a porcine faecal inoculum: competition and co-operation.

Sci Rep 2018 03 14;8(1):4546. Epub 2018 Mar 14.

ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD, 4072, Australia.

Recent studies show that a single or small number of intestinal microbes can completely degrade complex carbohydrates. This suggests a drive towards competitive utilisation of dietary complex carbohydrates resulting in limited microbial diversity, at odds with the health benefits associated with a diverse microbiome. This study investigates the enzymatic metabolism of wheat and rye arabinoxylans (AX) using in vitro fermentation, with a porcine faecal inoculum. Through studying the activity of AX-degrading enzymes and the structural changes of residual AX during fermentation, we show that the AX-degrading enzymes are mainly cell-associated, which enables the microbes to utilise the AX competitively. However, potential for cross-feeding is also demonstrated to occur by two distinct mechanisms: (1) release of AX after partial degradation by cell-associated enzymes, and (2) release of enzymes during biomass turnover, indicative of co-operative AX degradation. This study provides a model for the combined competitive-co-operative utilisation of complex dietary carbohydrates by gut microorganisms.
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http://dx.doi.org/10.1038/s41598-018-22818-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5852058PMC
March 2018

Male grower pigs fed cereal soluble dietary fibres display biphasic glucose response and delayed glycaemic response after an oral glucose tolerance test.

PLoS One 2018 1;13(3):e0193137. Epub 2018 Mar 1.

Queensland Alliance for Agriculture and Food Innovation, Centre for Nutrition and Food Sciences, The University of Queensland, St Lucia Brisbane, Australia.

Acute and sustained soluble dietary fibre (SDF) consumption are both associated with improved glucose tolerance in humans and animal models (e.g. porcine). However, the effects on glucose tolerance in grower pigs, adapted to diets with a combination of SDF have not been studied previously. In this experiment, cereal SDF wheat arabinoxylan (AX) and oat β-glucan (BG) were fed individually and in combination to determine the effect on glucose tolerance in jugular vein catheterized grower pigs. Five groups of Large White male grower pigs were fed highly digestible diets containing either 10% AX, 10% BG, 5% AX with 5% BG, a model cereal whole wheat flour (WWF), or a control wheat starch diet (WS) with no SDF. Blood was collected via jugular vein catheters over 240 minutes following a feed challenge and an oral glucose tolerance test (OGTT) on two separate days. Postprandial blood samples were used to determine plasma glucose, insulin, non-esterified fatty acids (NEFA), glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), peptide tyrosine tyrosine (PYY), ghrelin, glucagon and cortisol concentrations. No dietary effects on glycaemic response were observed following the feed challenge or the OGTT as determined by the area under the curve (AUC). A biphasic glucose and insulin response was detected for all pigs following the OGTT. The current study showed male grower pigs have tight glycaemic control and glucose tolerance regardless of diet. In addition, pigs fed the combined SDF had a reduced GIP response and delayed insulin peak following the feed challenge. Incretin (GLP-1 and GIP) secretion appeared asynchronous reflecting their different enteroendocrine cell locations and response to nutrient absorption.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193137PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5832219PMC
June 2018

Dietary pectin and mango pulp effects on small intestinal enzyme activity levels and macronutrient digestion in grower pigs.

Food Funct 2018 Feb;9(2):991-999

ARC Centre of Excellence in Plant Cell Walls, Queensland Alliance for Agriculture and Food Innovation, Centre for Nutrition and Food Sciences, The University of Queensland, St Lucia Brisbane, 4072, Australia.

The effects of refined pectin and mango pulp on macronutrient digestion and small intestinal enzyme activity were studied in grower pigs. Diets based on wheat starch with and without apple pectin or dried mango fruit pulp were fed to 30 grower pigs for 21 days. Pigs were euthanized two hours postprandially, and their gastrointestinal contents recovered. Starch and protein digestion as well as α-amylase activity were all increased in pigs fed pectin. In contrast, fat digestion, lipase and protease (trypsin) activities were all significantly reduced in these pigs. Pigs fed the mango fruit pulp diet had intermediate effects compared with pigs fed refined pectin and control diets. The data suggests that pectin has a significant effect on digestive enzyme activity and subsequent influence on macronutrient digestion. The fact that pectin caused either an increase (α-amylase) or decrease (lipase, protease) in enzyme activity in digesta, which either did (starch, lipid) or did not (protein) associate with residual nutrient differences illustrates the complexity of small intestinal responses to added fibre in diets.
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http://dx.doi.org/10.1039/c7fo00602kDOI Listing
February 2018

In vitro fermentation gas kinetics and end-products of soluble and insoluble cereal flour dietary fibres are similar.

Food Funct 2018 Feb;9(2):898-905

The University of Queensland, Centre for Nutrition and Food Sciences, ARC Centre of Excellence in Plant Cell Walls, Queensland Alliance for Agriculture and Food Innovation, St Lucia, 4072, Australia.

Insoluble dietary fibre is often considered to be fermented slower and to a lesser extent in (models for) the colon than soluble dietary fibre. However these comparisons are typically made for fibre components of different composition. In the case of fibre from refined cereal flours, there is little difference in fibre composition between soluble and insoluble forms, so effects of solubility on fermentation can be tested without this confounding factor. For each of wheat, rye, and hull-less barley, soluble and insoluble fibre fractions from refined flour and models for baking and extrusion had comparable in vitro fermentation rates and extents, with similar levels of short chain fatty acid metabolites. This study suggests that there should be little difference in the large intestinal nutritional functionality of the soluble and insoluble fibre fractions from cereal grain flours, either unprocessed or after baking or extrusion processing.
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http://dx.doi.org/10.1039/c7fo01724cDOI Listing
February 2018

Gut Fermentation of Dietary Fibres: Physico-Chemistry of Plant Cell Walls and Implications for Health.

Int J Mol Sci 2017 Oct 20;18(10). Epub 2017 Oct 20.

ARC Centre of Excellence for Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia QLD 4072, Australia.

The majority of dietary fibre (DF) originates from plant cell walls. Chemically, DF mostly comprise carbohydrate polymers, which resist hydrolysis by digestive enzymes in the mammalian small intestine, but can be fermented by large intestinal bacteria. One of the main benefits of DF relate to its fermentability, which affects microbial diversity and function within the gastro-intestinal tract (GIT), as well as the by-products of the fermentation process. Much work examining DF tends to focus on various purified ingredients, which have been extracted from plants. Increasingly, the validity of this is being questioned in terms of human nutrition, as there is evidence to suggest that it is the actual complexity of DF which affects the complexity of the GIT microbiota. Here, we review the literature comparing results of fermentation of purified DF substrates, with whole plant foods. There are strong indications that the more complex and varied the diet (and its ingredients), the more complex and varied the GIT microbiota is likely to be. Therefore, it is proposed that as the DF fermentability resulting from this complex microbial population has such profound effects on human health in relation to diet, it would be appropriate to include DF fermentability in its characterization-a functional approach of immediate relevance to nutrition.
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http://dx.doi.org/10.3390/ijms18102203DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5666883PMC
October 2017

An updated method for the jugular catheterization of grower pigs for repeated blood sampling following an oral glucose tolerance test.

Lab Anim 2017 Aug 1;51(4):397-404. Epub 2016 Jan 1.

1 ARC Centre of Excellence in Plant Cell Walls, Queensland Alliance for Agriculture and Food Innovation, Centre for Nutrition and Food Sciences, University of Queensland, St Lucia, Brisbane, Australia.

Jugular catheterization is a common procedure used under experimental conditions. However, there is considerable variation in the reported techniques, particularly for grower pigs (>40 kg and <60 kg) when larger volumes of blood per sample (>10 mL) are required. This paper provides a complete methodology including the use of current equipment and anaesthetic regimen for grower pigs. This surgical jugular catheterization method was carried out in 30 large white grower pigs. Firstly, the pigs were habituated to human handling for at least two weeks prior to surgery. Animals were sedated and anesthetized. Following intubation, an incision was made in the jugular fossa, and the jugular vein was located. A catheter was then inserted and fixated. The wound was stapled and the catheter line secured to the back of the neck. The pigs recovered fully from the surgery and the catheters remained patent for the duration of the blood sampling period (min 72 h). Twenty millilitres of blood were collected every 15 min, taking approximately 2 min per pig. No haemolysis was detected in any samples. Jugular catheterization of pigs using this procedure proved successful both in terms of animal recovery and quality of samples. Catheters remained patent and pigs remained calm during sampling.
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http://dx.doi.org/10.1177/0023677216682772DOI Listing
August 2017

Optimizing Prednisolone Loading into Distiller's Dried Grain Kafirin Microparticles, and In vitro Release for Oral Delivery.

Pharmaceutics 2017 May 19;9(2). Epub 2017 May 19.

School of Pharmacy, University of Queensland, 4072 Brisbane, Australia.

Kafirin microparticles have potential as colon-targeted delivery systems because of their ability to protect encapsulated material from digestive processes of the upper gastrointestinal tract (GIT). The aim was to optimize prednisolone loading into kafirin microparticles, and investigate their potential as an oral delivery system. Response surface methodology (RSM) was used to predict the optimal formulation of prednisolone loaded microparticles. Prednisolone release from the microparticles was measured in simulated conditions of the GIT. The RSM models were inadequate for predicting the relationship between starting quantities of kafirin and prednisolone, and prednisolone loading into microparticles. Compared to prednisolone released in the simulated gastric and small intestinal conditions, no additional drug release was observed in simulated colonic conditions. Hence, more insight into factors affecting drug loading into kafirin microparticles is required to improve the robustness of the RSM model. This present method of formulating prednisolone-loaded kafirin microparticles is unlikely to offer clinical benefits over commercially available dosage forms. Nevertheless, the overall amount of prednisolone released from the kafirin microparticles in conditions simulating the human GIT demonstrates their ability to prevent the release of entrapped core material. Further work developing the formulation methods may result in a delivery system that targets the lower GIT.
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http://dx.doi.org/10.3390/pharmaceutics9020017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5489934PMC
May 2017

Addition of arabinoxylan and mixed linkage glucans in porcine diets affects the large intestinal bacterial populations.

Eur J Nutr 2017 Sep 11;56(6):2193-2206. Epub 2016 Jul 11.

ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences (CNAFS), Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, St. Lucia, QLD, 4072, Australia.

Purpose: To investigate the effects of two cereal soluble dietary fibres (SDF), wheat arabinoxylan (AX) and oat-mixed linkage glucans (MLG), on fermentative end-products and bacterial community profiles of the porcine caecum (Cae) and distal colon (DC). We hypothesised that feeding pigs these SDF would stimulate Cae and DC carbohydrate fermentation, resulting in a modification of the resident bacterial communities.

Methods: Five groups of six pigs were each fed one diet based on wheat starch (WS) only, or treatment diets in which some WS was replaced by 10 % AX, or 10 % MLG, a combination of 5 % AX:5 % MLG (AXMLG), or completely replaced with ground whole wheat. Post-euthanasia, Cae and DC digesta were collected for analysis of fermentative end-products, and bacterial community profiles were determined by 16S rRNA gene amplicon 454 pyrosequencing.

Results: Across all the SDF-containing diets, predominantly in the proximal region of the large intestine, Prevotella, Lactobacillus, Mitsuokella and Streptococcus were most significantly influenced (P < 0.05), while notable changes were observed for the Ruminococcaceae and Lachnospiraceae families in the Cae and DC. The addition of MLG or AXMLG had the greatest effect of influencing bacterial profiles, reducing sequence proportions assigned to the genus Clostridium, considered detrimental to gut health, with associated increases in short-chain fatty acid and reduced ammonia concentrations.

Conclusions: This study demonstrated how the cereal SDF AX and MLG altered the large intestinal bacterial community composition, particularly proximally, further giving insights into how diets rich in specific complex carbohydrates shift the bacterial population, by increasing abundance and promoting greater diversity of those bacteria considered beneficial to gut health.
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http://dx.doi.org/10.1007/s00394-016-1263-4DOI Listing
September 2017

Rheological and microstructural properties of porcine gastric digesta and diets containing pectin or mango powder.

Carbohydr Polym 2016 09 13;148:216-26. Epub 2016 Apr 13.

ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, 4072, QLD, Australia. Electronic address:

Hydrated polysaccharides and their assemblies are known to modulate gastric emptying rate due to their capacity to change the structural and rheological properties of gastric contents (digesta). In the present study, we investigated the rheological and microstructural properties of gastric digesta from pigs fed with diets incorporating mango powder or pectin, and compared results with those from hydrated diets of the same water content, in order to investigate the origins for rheological changes in the pig stomach. All of the hydrated diets and gastric digesta were particle-dominated suspensions, generally showing weak gel or more solid-like behavior with the storage modulus (G') always greater than loss modulus (G") under small deformation oscillatory measurements, and with small deformation viscosity greater than steady shear viscosity (i.e. non-Cox-Merz superposition). Although significant rheological differences were observed between the hydrated diets, rheological parameters for gastric digesta were similar for all diets, indicative of a rheological homeostasis in the pig stomach. Whilst the addition of gastric mucin (20mg/mL) to control and mango diets altered the rheology to match the gastric digesta rheology, the effect of mucin on the pectin-containing diet was negligible. The viscous effect of pectin also hindered the action of alpha amylase as observed from relatively less damaged starch granules in pectin digesta compared to mango and control digesta. Based on the experimental findings that the rheology of gastric digesta differs from hydrated diets of the same water content, the current study revealed composition-dependent complex behavior of gastric digesta in vivo, suggesting that the rheology of food products or ingredients may not necessarily reflect the rheological effect when ingested.
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http://dx.doi.org/10.1016/j.carbpol.2016.04.037DOI Listing
September 2016

Microbial biotransformation of polyphenols during in vitro colonic fermentation of masticated mango and banana.

Food Chem 2016 Sep 30;207:214-22. Epub 2016 Mar 30.

ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, 4072, Australia. Electronic address:

Mango and banana cell structures, which survived in vivo mastication and in vitro gastrointestinal digestion, were fermented in vitro for 48h. For both fruits, flavonoids and phenolic acids were liberated and underwent microbial metabolism involving ring fission, dehydroxylation and decarboxylation. UHPLC-PDA/Q-ToF-MS profiles revealed rapid degradation (72-78%) of most intact precursors (epicatechin and several unidentified compounds) within 10h, before the exponential phase of the cumulative gas production. Concomitant formation of catabolites (e.g. 4-hydroxyphenylacetic acid) occurred within 4-8h, while metabolism of catechin derivative and 3-(4-hydroxyphenyl)propanoic acid continued slowly for at least 48h, suggesting intact plant cell walls can be a controlling factor in microbial susceptibility. Untargeted PCA and OPLS-DA demonstrated clear classifications in the compositional fruit type and compound profiles as a function of time. Clusters and distinct discriminating compounds were recognised, which could lead to subsequent biomarker identification for establishing differences in polyphenol microbial metabolism of various fruit matrices.
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http://dx.doi.org/10.1016/j.foodchem.2016.03.108DOI Listing
September 2016

Soluble arabinoxylan enhances large intestinal microbial health biomarkers in pigs fed a red meat-containing diet.

Nutrition 2016 Apr 2;32(4):491-7. Epub 2015 Nov 2.

The University of Queensland, Australian Research Council Centre of Excellence in Plant Cell Walls, QAAFI Centre for Nutrition and Food Sciences, St. Lucia, Queensland, Australia.

Objectives: The aim of this study was to investigate how moderately increased dietary red meat combined with a soluble fiber (wheat arabinoxylan [AX]) alters the large intestinal microbiota in terms of fermentative end products and microbial community profiles in pigs.

Methods: Four groups of 10 pigs were fed Western-type diets containing two amounts of red meat, with or without a solubilized wheat AX-rich fraction for 4 wk. After euthanasia, fermentative end products (short-chain fatty acids, ammonia) of digesta from four sections of large intestine were measured. Di-amino-pimelic acid was a measure of total microbial biomass, and bacterial profiles were determined using a phylogenetic microarray. A factorial model determined effects of AX and meat content.

Results: Arabinoxylan was highly fermentable in the cecum, as indicated by increased concentrations of short-chain fatty acids (particularly propionate). Protein fermentation end products were decreased, as indicated by the reduced ammonia and branched-chain ratio although this effect was less prominent distally. Microbial profiles in the distal large intestine differed in the presence of AX (including promotion of Faecalibacterium prausnitzii), consistent with an increase in carbohydrate versus protein fermentation. Increased di-amino-pimelic acid (P < 0.0001) suggested increased microbial biomass for animals fed AX.

Conclusions: Solubilized wheat AX has the potential to counteract the effects of dietary red meat by reducing protein fermentation and its resultant toxic end products such as ammonia, as well as leading to a positive shift in fermentation end products and microbial profiles in the large intestine.
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http://dx.doi.org/10.1016/j.nut.2015.10.008DOI Listing
April 2016

Circulating triglycerides and bile acids are reduced by a soluble wheat arabinoxylan via modulation of bile concentration and lipid digestion rates in a pig model.

Mol Nutr Food Res 2016 Mar 19;60(3):642-51. Epub 2016 Jan 19.

ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland.

Scope: Soluble dietary fibres have shown to have lipid reducing properties. However, their mechanisms of action are still unclear. The present study investigated how a soluble wheat arabinoxylan-rich fraction (AXRF) fed to pigs used as a human model reduced blood triglycerides.

Methods And Results: After 4 weeks on the experimental diets, blood from the jugular (JV) and hepatic portal (HPV) veins, bile from the gall bladder, and digesta samples from four sites of the small intestine (SI) and cecum were collected. The results showed that the AXRF significantly decreased the concentrations of total bile acid (BA) in the HPV (p < 0.01), JV (p < 0.01), bile (p < 0.05) and SI (p < 0.05), but with no effect on ileal BAs excretion flux. Furthermore, blood triglyceride (TAG) levels were also lower with AXRF (p < 0.01) but with no significant effects on LDL-, HDL- or total cholesterol levels. The lower plasma TAG concentration was consistent with the reduced/delayed digestion and absorption of TAG with the AXRF (total fatty acid and MUFA p < 0.01; unsaturated fatty acid p < 0.05).

Conclusion: The results suggest that AXRF reduced the levels of circulating BAs which slowed down the digestion of TAG and absorption of free fatty acids, with consequent reduction in blood TAG. Reduction in circulating bile acids by arabinoxylan causes reduction in lipids digestion and absorption.
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http://dx.doi.org/10.1002/mnfr.201500686DOI Listing
March 2016

Soluble arabinoxylan alters digesta flow and protein digestion of red meat-containing diets in pigs.

Nutrition 2015 Sep 7;31(9):1141-7. Epub 2015 Apr 7.

The University of Queensland, ARC CoE Plant Cell Walls, Centre for Nutrition and Food Sciences, St. Lucia, Queensland, Australia; The University of Queensland, School of Agriculture and Food Sciences, Gatton, Queensland, Australia.

Objectives: The aim of this study was to investigate how a moderate increase in dietary meat content combined (or not) with soluble fibre would influence protein digestion as well as digesta characteristics and flow.

Methods: Four groups of pigs were fed Western-style diets (high-protein/high-fat) containing two types of barbecued red meat, one with and one without a wheat arabinoxylan-rich fraction. After 4 wk, digesta samples were collected from small and large intestinal sites and analyzed for protein, amino acids, dry matter, and acid-insoluble ash. Tissue samples were also collected from each site.

Results: Arabinoxylan consumption led to somewhat lower apparent protein digestibility within the small and large intestines as well as shorter mean retention times. This suggests that the lowered protein digestibility is due, at least partly, to shorter access time to digestive proteases and absorptive surfaces. Additionally, digesta mass was higher in pigs fed arabinoxylan while dry matter (%) was lower, indicating an increased digesta water-holding capacity due to the presence of a soluble dietary fiber.

Conclusion: Data showed that solubilized wheat arabinoxylan provides potential health benefits through decreased protein digestibility, increased digesta mass, and reduced mean retention time, even for diets with a moderately higher protein content. These factors are associated with efficiency of digestion and satiety, both of which have implications for prevention of obesity and other health disorders.
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http://dx.doi.org/10.1016/j.nut.2015.03.006DOI Listing
September 2015

In vitro fermentation of chewed mango and banana: particle size, starch and vascular fibre effects.

Food Funct 2015 Aug 28;6(8):2464-74. Epub 2015 Jul 28.

ARC Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, 4072, Australia.

Fruits (and vegetables) contain cellular structures that are not degraded by human digestive enzymes. Therefore, the structure of the insoluble fraction of swallowed fruits is mostly retained until intestinal microbial fermentation. In vitro fermentation of mango and banana cell structures, which survived in vivo mastication and in vitro gastrointestinal digestion, were incubated with porcine faecal inoculum and showed intensive metabolic activity. This included degradation of cell walls, leading to the release of encapsulated cell contents for further microbial metabolism. Production of cumulative gas, short chain fatty acids and ammonia were greater for mango than for banana. Microscopic and spectroscopic analyses showed this was due to a major fermentation-resistant starch fraction present in banana, that was absent in mango. This study demonstrated distinctive differences in the fermentability of banana and mango, reflecting a preferential degradation of (parenchyma) fleshy cell walls over resistant starch in banana, and the thick cellulosic vascular fibres in mango.
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http://dx.doi.org/10.1039/c5fo00363fDOI Listing
August 2015

Role of intestinal microbiota in the generation of polyphenol-derived phenolic acid mediated attenuation of Alzheimer's disease β-amyloid oligomerization.

Mol Nutr Food Res 2015 Jun 27;59(6):1025-40. Epub 2015 Apr 27.

Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NJ, USA.

Scope: Grape seed polyphenol extract (GSPE) is receiving increasing attention for its potential preventative and therapeutic roles in Alzheimer's disease (AD) and other age-related neurodegenerative disorders. The intestinal microbiota is known to actively convert many dietary polyphenols, including GSPE, to phenolic acids. There is limited information on the bioavailability and bioactivity of GSPE-derived phenolic acid in the brain.

Methods And Results: We orally administered GSPE to rats and investigated the bioavailability of 12 phenolic acids known to be generated by microbiota metabolism of anthocyanidins. GSPE treatment significantly increased the content of two of the phenolic acids in the brain: 3-hydroxybenzoic acid and 3-(3´-hydroxyphenyl)propionic acid, resulting in the brain accumulations of the two phenolic acids at micromolar concentrations. We also provided evidence that 3-hydroxybenzoic acid and 3-(3´-hydroxyphenyl)propionic acid potently interfere with the assembly of β-amyloid peptides into neurotoxic β-amyloid aggregates that play key roles in AD pathogenesis.

Conclusion: Our observation suggests important contribution of the intestinal microbiota to the protective activities of GSPE (as well as other polyphenol preparations) in AD. Outcomes from our studies support future preclinical and clinical investigations exploring the potential contributions of the intestinal microbiota in protecting against the onset/progression of AD and other neurodegenerative conditions.
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http://dx.doi.org/10.1002/mnfr.201400544DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4498582PMC
June 2015

Microbial metabolites, but not other phenolics derived from grape seed phenolic extract, are transported through differentiated Caco-2 cell monolayers.

Food Chem 2013 Jun 8;138(2-3):1564-73. Epub 2012 Nov 8.

University of Queensland, School of Agriculture and Food Sciences, Brisbane, Queensland 4072, Australia.

Grape seed phenolic extract (GSE) is predicted to have health benefits, even though its bioavailability, including digestibility, permeability and ultimate metabolism, are still poorly understood. In vitro gastric and pancreatic digestion and in vitro ileal and faecal fermentation were combined with Caco-2 cell permeability studies for GSE samples. Qualitatively, there was no change in type/number of GSE compounds following gastric and pancreatic digestion and LC-MS analysis. However, the monomers were significantly (P<0.05) increased after gastric digestion, along with a significant (P<0.05) decrease in polymers. In addition, all forms of phenolic compounds decreased following pancreatic digestion. However, none of the original GSE phenolic compounds passed the Caco-2 cell monolayer, since all were recovered in the apical compartment. In contrast, the two intestinal microbiota metabolites with deprotonated molecular weights of [M-H]-165/121 and 193/175, that were found both in the ileal and faecal fermented samples, passed the Caco-2 cell monolayer.
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http://dx.doi.org/10.1016/j.foodchem.2012.09.103DOI Listing
June 2013

Different concentrations of grape seed extract affect in vitro starch fermentation by porcine small and large intestinal inocula.

J Sci Food Agric 2013 Jan 6;93(2):276-83. Epub 2012 Jul 6.

School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland, Australia.

Background: Grape seed extract (GSE) phenolics have potential health-promoting properties, either from compounds present within the extract, or metabolites resulting from gastrointestinal tract (GIT) fermentation of these compounds. This study describes how GSE affected the kinetics and end-products of starch fermentation in vitro using pig intestinal and fecal inocula. Six GSE concentrations (0, 60, 125, 250, 500, and 750 µg ml⁻¹ were fermented in vitro by porcine ileal and fecal microbiota using starch as the energy source. Cumulative gas production, and end-point short chain fatty acids and ammonia were measured.

Results: GSE phenolics altered the pattern (gas kinetics, and end-products such as SCFA and NH₄⁺) of starch fermentation by both inocula, at concentrations above 250 µg ml⁻¹ . Below this level, neither inoculum showed any significant (P > 0.05) effect of the GSE.

Conclusion: The results show that GSE phenolics at a concentration over 250 µg ml⁻¹ can have measurable effects on microbial activity in an in vitro fermentation system, as evidenced by the changes in kinetics and end-products from starch fermentation. This suggests that fermentation patterns could be conceivably shifted in the actual GIT, though further evidence will be required from in vivo studies.
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http://dx.doi.org/10.1002/jsfa.5753DOI Listing
January 2013

Faster fermentation of cooked carrot cell clusters compared to cell wall fragments in vitro by porcine feces.

J Agric Food Chem 2012 Mar 19;60(12):3282-90. Epub 2012 Mar 19.

CSIRO Food and Nutritional Sciences, 671 Sneydes Road, Werribee, Victoria 3030, Australia.

Plant cell walls are the major structural component of fruits and vegetables, which break down to cell wall particles during ingestion (oral mastication) or food processing. The major health-promoting effect of cell walls occurs when they reach the colon and are fermented by the gut microbiota. In this study, the fermentation kinetics of carrot cell wall particle dispersions with different particle size and microstructure were investigated in vitro using porcine feces. The cumulative gas production and short-chain fatty acids (SCFAs) produced were measured at time intervals up to 48 h. The results show that larger cell clusters with an average particle size (d(0.5)) of 298 and 137 μm were more rapidly fermented and produced more SCFAs and gas than smaller single cells (75 μm) or cell fragments (50 μm), particularly between 8 and 20 h. Confocal microscopy suggests that the junctions between cells provides an environment that promotes bacterial growth, outweighing the greater specific surface area of smaller particles as a driver for more rapid fermentation. The study demonstrates that it may be possible, by controlling the size of cell wall particles, to design plant-based foods for fiber delivery and promotion of colon fermentation to maximize the potential for human health.
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http://dx.doi.org/10.1021/jf204974sDOI Listing
March 2012