Publications by authors named "Michael J Gidley"

156 Publications

Molecular-structure evolution during in vitro fermentation of granular high-amylose wheat starch is different to in vitro digestion.

Food Chem 2021 May 25;362:130188. Epub 2021 May 25.

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

This study investigates the evolution of the distributions of whole molecular size and of chain length of granular wheat starches (37 ~ 93% amylose content), subjected to in vitro fermentation with a porcine faecal inoculum or digestion with pancreatic enzymes. The results showed that the molecular structures of high-amylose starch (HAS) unfermented residues largely remained unchanged during the fermentation process, while wild-type starch (37% amylose content) showed a preferential degradation of the amylopectin fraction. In contrast, under simulated digestion conditions, the undigested residues of HAS showed structural changes, including a decrease in amylose content, a shift of amylose peak position towards lower degrees of polymerisation, and an enzyme-resistant fraction. These changes of starch structure are likely to be dependent on the different starch-degrading enzyme activities present in pancreatic vs. microbial systems. Molecular changes in response to fermentation metabolism revealed by size-exclusion chromatography can help understand the microbial utilization of resistant starch.
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http://dx.doi.org/10.1016/j.foodchem.2021.130188DOI Listing
May 2021

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

Towards personalised saliva spectral fingerprints: Comparison of mid infrared spectra of dried and whole saliva samples.

Spectrochim Acta A Mol Biomol Spectrosc 2021 May 9;253:119569. Epub 2021 Feb 9.

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

The aims of this study were to compare two sample presentations (dry and whole) as well as the effects of both gender and age on the mid infrared (MIR) fingerprint spectra of human saliva. Unstimulated saliva was collected from 52 Female (31 subjects, aged 40.9 ± 14.6 year) and Male (21 subjects, aged 34 ± 11.8 year) participants, stored frozen, and subsequently thawed and analysed by MIR spectroscopy as whole and dried saliva, respectively. Data were analysed by means of principal components analysis (PCA) and partial least squares (PLS) to interpret and compare the effects of presentation (dry vs whole), age and gender on the MIR spectra of saliva. Interpretation of the MIR spectra of both whole and dried samples revealed specific characteristic and different spectral signals when gender and age were compared in the amide I and amide II of proteins (e.g. albumin) and DNA. While whole saliva analysis might be more convenient for rapid test, dried saliva spectra were more consistent across replicates, demonstrating greater ability to distinguish individual differences. The interpretation of the PCA and PLS loadings of both whole and dried saliva samples allowed identification of specific MIR regions associated with age and gender of participants between 1000 cm and 1800 cm. In particular, the MIR regions associated with the absorption of polysaccharides, glycosylated proteins, and nucleic acid phosphate groups present in saliva were the most dominant. This paper demonstrates that MIR spectroscopy can be used to measure saliva samples and to interpret individual differences in participants due to age in either dry or whole samples. No clear trends were observed in the MIR spectra of the samples associated with gender when all samples were analysed together. However, PLS regression models were able to predict gender in a subset of samples having similar age. The approach described in this study shows promise for potentially using saliva as a tool in food studies (e.g. saliva interactions between food and consumers).
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http://dx.doi.org/10.1016/j.saa.2021.119569DOI Listing
May 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

Nutritional, anti-nutritional, antioxidant, physicochemical and functional characterization of Australian acacia seed: effect of species and regions.

J Sci Food Agric 2021 Jan 25. Epub 2021 Jan 25.

Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Coopers Plains, QLD, Australia.

Background: Acacia seed (AS) is an underutilized legume widely distributed in the world, with majority of the species (>70%) found in Australia. Generally, the seeds are not only rich in protein, dietary fibre and potassium, but also possess anti-nutritional compounds. In recent years, there have been an increase in the cultivation of some Australian acacia species such as Acacia victoriae, Acacia cowleana and Acacia coriacea from different regions. However, there is limited information on the composition, anti-nutrients, antioxidant and functional properties of flour from these widely grown Australian AS species. Thus, the present study aimed to assess the properties of these Australian AS species from different geographical regions.

Results: The A. cowleana and A. coriacea were characterized by high protein, fat, potassium and soluble carbohydrate. However, higher starch and fibre contents were present in A. victoriae. Greater amounts of anti-nutrients, total phenolics and flavonoids were found in A. cowleana and A. coriacea seeds, whereas A. victoriae had higher 2,2-diphenyl-1-picrylhydrazyl radical-scavenging capacity. A. victoriae and A. coriacea demonstrated the highest water absorption and solubility index, respectively. However, A. cowleana showed the highest oil absorption index. There was less variation in the composition and properties within species from different regions.

Conclusion: All samples showed promising nutritional characteristics, although with sufficient diversity to indicate that Australian acacia seeds can be utilized to develop a range of new (functional) food products. Overall, the information obtained will help the food industries with the selection of AS species for food application.
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http://dx.doi.org/10.1002/jsfa.11113DOI Listing
January 2021

Depletion and bridging flocculation of oil droplets in the presence of β-glucan, arabinoxylan and pectin polymers: Effects on lipolysis.

Carbohydr Polym 2021 Mar 13;255:117491. Epub 2020 Dec 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, Brisbane, Queensland, 4072, Australia. Electronic address:

The aim of this study was to investigate the influence of food polysaccharides from different sources on microstructural and rheological properties, and in vitro lipolysis of oil-in-water emulsions of canola oil stabilised by whey protein isolate. The polysaccharides used were β-glucan (BG) from oat, arabinoxylan (AX) from wheat, and pectin (PTN) from apple. All polysaccharides added at 1 % w/v increased the viscosity of emulsions and promoted flocculation but with different mechanisms, BG and AX by depletion flocculation and PTN by bridging flocculation. Depletion flocculation was associated with an increase in viscosity of BG or AX-stabilised emulsions compared with BG/AX alone, whereas bridging flocculation with PTN caused a decrease in viscosity. All three polysaccharides reduced lipid digestion rate and extent, but the bridging flocculation induced by PTN had the greatest effect. This study has implications for better understanding the influence of carbohydrate polymers from cereals and fruits on lipid digestibility.
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http://dx.doi.org/10.1016/j.carbpol.2020.117491DOI Listing
March 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

Wood hemicelluloses exert distinct biomechanical contributions to cellulose fibrillar networks.

Nat Commun 2020 09 17;11(1):4692. Epub 2020 Sep 17.

Wallenberg Wood Science Centre, Department of Fibre and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden.

Hemicelluloses, a family of heterogeneous polysaccharides with complex molecular structures, constitute a fundamental component of lignocellulosic biomass. However, the contribution of each hemicellulose type to the mechanical properties of secondary plant cell walls remains elusive. Here we homogeneously incorporate different combinations of extracted and purified hemicelluloses (xylans and glucomannans) from softwood and hardwood species into self-assembled networks during cellulose biosynthesis in a bacterial model, without altering the morphology and the crystallinity of the cellulose bundles. These composite hydrogels can be therefore envisioned as models of secondary plant cell walls prior to lignification. The incorporated hemicelluloses exhibit both a rigid phase having close interactions with cellulose, together with a flexible phase contributing to the multiscale architecture of the bacterial cellulose hydrogels. The wood hemicelluloses exhibit distinct biomechanical contributions, with glucomannans increasing the elastic modulus in compression, and xylans contributing to a dramatic increase of the elongation at break under tension. These diverging effects cannot be explained solely from the nature of their direct interactions with cellulose, but can be related to the distinct molecular structure of wood xylans and mannans, the multiphase architecture of the hydrogels and the aggregative effects amongst hemicellulose-coated fibrils. Our study contributes to understanding the specific roles of wood xylans and glucomannans in the biomechanical integrity of secondary cell walls in tension and compression and has significance for the development of lignocellulosic materials with controlled assembly and tailored mechanical properties.
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http://dx.doi.org/10.1038/s41467-020-18390-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7499266PMC
September 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

Protein-starch matrix plays a key role in enzymic digestion of high-amylose wheat noodle.

Food Chem 2021 Jan 1;336:127719. Epub 2020 Aug 1.

The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia; Department of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia. Electronic address:

Wheat flour, consisting of a complex matrix of starch and protein, is used as a representative model of whole food here to investigate the binary interaction in relation to amylose level and hydrothermal treatment in noodles as a food exemplar. Noodle made of high-amylose wheat (HAW) flour showed an eight-fold higher resistant starch content, compared to the wild type. Protein removal under simulated intestinal digestion conditions resulted in higher starch digestion rate coefficients in raw and cooked flours. In cooked flours, the substrate becomes similarly accessible to digestive enzymes regardless of protein removal. The results indicate that the increased protein content in native HAW flour and thermal stability of starch in HAW noodles lead to higher food integrity and consequently enhance the resistance against α-amylase digestion. Overall, the study suggests that a diversity of starch-protein interactions in wheat-based food products underlies the nutritional value of natural whole foods.
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http://dx.doi.org/10.1016/j.foodchem.2020.127719DOI Listing
January 2021

High-amylose wheat starch: Structural basis for water absorption and pasting properties.

Carbohydr Polym 2020 Oct 4;245:116557. Epub 2020 Jun 4.

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

High-amylose wheat starch (HAWS) and flour (HAWF) have the potential to deliver food products with enhanced nutritional functionality, but structure/function relationships are not well understood. We report the structural bases for differences in water absorption and pasting properties for HAWS and HAWF (amylose contents 71-84 %) compared with wild-type (WTWS/WTWF). With higher amylose content, the proportion of longer amylopectin chains with DP > 25 increased. Both the degree of branching and the branch lengths of amylose were lower for HAWS than WTWS. Compared with WTWF, HAWF contained less total starch, more protein, had lower peak viscosity by high-temperature RVA, lower dough development time and stability time and higher water absorption by Farinograph. Water absorption by HAWS was ∼1.5 times greater than for WTWS, suggesting loose packing of polymers within HAWS granules. Consistent with this, crystallinity and birefringence of starch granules were lower in HAWS.
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http://dx.doi.org/10.1016/j.carbpol.2020.116557DOI Listing
October 2020

Formation of Cellulose-Based Composites with Hemicelluloses and Pectins Using Komagataeibacter Fermentation.

Methods Mol Biol 2020 ;2149:73-87

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, Brisbane, QLD, Australia.

Komagataeibacter xylinus synthesizes cellulose in an analogous fashion to plants. Through fermentation of K. xylinus in media containing cell wall polysaccharides from the hemicellulose and/or pectin families, composites with cellulose can be produced. These serve as general models for the assembly, structure, and properties of plant cell walls. By studying structure/property relationships of cellulose composites, the effects of defined hemicellulose and/or pectin polysaccharide structures can be investigated. The macroscopic nature of the composites also allows composite mechanical properties to be characterized.The method for producing cellulose-based composites involves reviving and then culturing K. xylinus in the presence of desired hemicelluloses and/or pectins. Different conditions are required for construction of hemicellulose- and pectin-containing composites. Fermentation results in a floating mat or pellicle of cellulose-based composite that can be recovered, washed, and then studied under hydrated conditions without any need for intermediate drying.
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http://dx.doi.org/10.1007/978-1-0716-0621-6_5DOI Listing
March 2021

Starch granular protein of high-amylose wheat gives innate resistance to amylolysis.

Food Chem 2020 Nov 12;330:127328. Epub 2020 Jun 12.

The University of Queensland, Center for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia; Department of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia. Electronic address:

Granular protein is an important structural feature in determining starch digestibility. High-amylose wheat starch (HAWS) with >80% amylose content contains more granular protein than wild-type starch. As analyzed by mass spectrometry-based proteomics, granular-bound starch synthase (GBSS) is the major granular protein in isolated starch materials. GBSS content increases with amylose content (Spearman's correlation, p < 0.05), whereas the abundance relative to other proteins is similar among starches. Multiple amylase inhibitors were also identified. From Michaelis-Menten analysis, HAWS has a similar K (Michaelis constant) as wild type, suggesting initial enzymatic binding is similar. After the pre-digestion of proteins, wild type had a greater change in starch digestibility than HAWS, probably due to the latter having 'thicker' granular-protein layers and higher enzymatic resistance of substrate per se. Overall, the study suggests that the greater granular protein content in HAWS is a factor that contributes to slower amylolysis compared to wild type.
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http://dx.doi.org/10.1016/j.foodchem.2020.127328DOI Listing
November 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

The contribution of β-glucan and starch fine structure to texture of oat-fortified wheat noodles.

Food Chem 2020 Sep 21;324:126858. Epub 2020 Apr 21.

Queensland Alliance for Agriculture and Food Innovation (QAAFI), Centre for Nutrition and Food Sciences, The University of Queensland, Qld 4067, Australia; Department of Food Science and Technology, University of California Davis, CA 95616, USA.

Wheat flour noodles are sometimes fortified with β-glucan for nutritional value, but this can decrease eating quality. The contributions of β-glucan and starch molecular fine structure to physicochemical properties of wholemeal oat flour and to the texture of oat-fortified white salted noodles were investigated here. Hardness of oat-fortified noodles was controlled by the longer amylopectin chains (DP ≥ 26) and amount of longer amylose chains (DP ≥ 1000). Higher levels of β-glucan, in the range from 3.1 to 5.2%, result in increased noodle hardness. Pasting viscosities of wholemeal oat flour positively correlate with the hardness of oat-fortified noodles. The swelling power of oat flour is not correlated with either pasting viscosities of oat flour or noodle hardness. Longer amylopectin chains and the amount of longer amylose chains both control the pasting viscosities of oat flour, which in turn affect noodle texture. This provides new means, based on starch and β-glucan molecular structure, to choose oats with optimal starch structure and β-glucan content for targeted oat-fortified noodle quality.
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http://dx.doi.org/10.1016/j.foodchem.2020.126858DOI Listing
September 2020

Functional Genomic Validation of the Roles of in Rice Endosperm.

Front Genet 2020 2;11:289. Epub 2020 Apr 2.

CSIRO Agriculture and Food, Canberra, ACT, Australia.

The enzyme starch synthase IIa (SSIIa) in cereals has catalytic and regulatory roles during the synthesis of amylopectin that influences the functional properties of the grain. Rice endosperm SSIIa is more active in accessions compared to lines due to functional SNP variations in the coding region of the structural gene. In this study, downregulating the expression of -type SSIIa in Nipponbare endosperm resulted in either shrunken or opaque grains with an elevated proportion of A-type starch granules. Shrunken seeds had severely reduced starch content and could not be maintained in succeeding generations. In comparison, the opaque grain morphology was the result of weaker down-regulation of which led to an elevated proportion of short-chain amylopectin (DP 6-12) and a concomitant reduction in the proportion of medium-chain amylopectin (DP 13-36). The peak gelatinization temperature of starch and the estimated glycemic score of cooked grain as measured by the starch hydrolysis index were significantly reduced. These results highlight the important role of medium-chain amylopectin in influencing the functional properties of rice grains, including its digestibility. The structural, regulatory and nutritional implications of down-regulated -type in rice endosperm are discussed.
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http://dx.doi.org/10.3389/fgene.2020.00289DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7142255PMC
April 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

In Vitro Digestion of Apple Tissue Using a Dynamic Stomach Model: Grinding and Crushing Effects on Polyphenol Bioaccessibility.

J Agric Food Chem 2020 Jan 31;68(2):574-583. Epub 2019 Dec 31.

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 , Queensland 4072 , Australia.

Food structure is a key determinant for the release of phenolic compounds during gastric and intestinal digestion. We evaluated the bioaccessibility of polyphenols from apple tissue during gastric digestion in vitro from bio-mechanical perspectives including the effects of gastric juice and mucin on the apple tissue matrix under simulated stomach peristalsis. The gastric model system was effective in releasing polyphenols because of simultaneous compression and extrusion, with 3 times higher release from coarse than from fine particles. However, bioaccessibility of polyphenols was reduced up to 44% in the presence of both cell walls and gastric mucin. Most individual phenolic molecules were gradually released and were stable in the gastric environment, except for procyanidin B2. The study suggests that the bioaccessibility of polyphenols from apples in the upper digestive tract is dependent on mechanical disintegration and the residual matrix present in the swallowed bolus.
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http://dx.doi.org/10.1021/acs.jafc.9b05649DOI 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

A more general approach to fitting digestion kinetics of starch in food.

Carbohydr Polym 2019 Dec 24;225:115244. Epub 2019 Aug 24.

Joint International Research Laboratory of Agriculture and Agri-Product Safety, College of Agriculture, Yangzhou University, Yangzhou, 225009, Jiangsu Province, China; The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia. Electronic address:

Two models for the digestion of starch in foods are considered: sequential, where two or more reactions follow one another, and parallel, where they occur simultaneously. Each reaction is assumed to be first-order, and to be characterized by a rate coefficient and a digestible fraction. For parallel kinetics, a new fitting method is developed; methods for sequential reactions are already available, based on the "logarithm of slopes" technique. Least-squares fitting methods for each are set out, which identify the uncertainties associated with each rate parameter, so that one can see if one has assumed too many or too few processes. The methods gave robust results with synthetic data, and were applied to real in vitro digestion data for wheat starches with up to 93% amylose. The combination of parallel and sequential models provides a general approach to investigating the kinetics of starch digestion in food.
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http://dx.doi.org/10.1016/j.carbpol.2019.115244DOI Listing
December 2019

Starch branching enzymes contributing to amylose and amylopectin fine structure in wheat.

Carbohydr Polym 2019 Nov 10;224:115185. Epub 2019 Aug 10.

The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia; Joint International Research Laboratory of Agriculture and Agri-Product Safety, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu Province, China. Electronic address:

Starch branching enzymes (SBEs) play a major role in determining starch molecular structure in cereal endosperm. This study investigates how SBEIIs contribute to the chain-length distributions (CLDs) of both amylopectin and amylose, obtained by enzymatic debranching of native starch. Wheat starches with low (37%) to high (93%) amylose content were obtained through altering SBEII in planta. Multiple components were detected in both amylose and amylopectin CLDs. Model fitting of these CLDs reveals a quantitative association between the enzyme activities in amylopectin and amylose. SBEIIa modifies shorter branches (degree of polymerization DP ≲ 12) in amylopectin and longer amylose chains with a CLD peak at ˜3000 DP. SBEIIb acts on longer branches (DP≲ 32) in amylopectin, while its effect on amylose fine structure is not significant. Using both the amylose and amylopectin models to analyze the CLD reveals connections between amylose and amylopectin in wheat starch biosynthesis.
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http://dx.doi.org/10.1016/j.carbpol.2019.115185DOI Listing
November 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

Cellular barriers in apple tissue regulate polyphenol release under different food processing and in vitro digestion conditions.

Food Funct 2019 May;10(5):3008-3017

Key Laboratory of Plant Cell Walls & Plant Resistance, Molecular Analysis & Genetic Improvement Center, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.

Polyphenol released from food matrices is the first stage for their potential beneficial effects on human health. To better understand how natural barriers such as plant cell membranes and cell walls modulate polyphenol release, the major phenolic compounds within cells in apple pieces were directly localized, and their release under different thermal processing and acidic digestion conditions measured. The plasma membrane was found to be more thermally stable than the tonoplast, with membrane disruption occurring above 60 °C after processing for more than 10 min, acting as an efficient trigger for increased polyphenol release from 15% to more than 50%. Confocal microscopy of phenolic compounds in apple cells after thermal processing showed a clear relocation from uniform distribution in vacuoles to localization around cell walls, suggesting that the non-released polyphenols were cell wall associated. No additional polyphenols were released as a result of acidic conditions (pH 2-5) likely to be encountered in the stomach. Processing (thermal, pH) promoted polyphenol release by disrupting intracellular barriers, thus increasing the contact with cell walls and modulating bioaccessibility by controlling the interactions between cell walls and polyphenols.
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http://dx.doi.org/10.1039/c8fo02528bDOI Listing
May 2019

High-Amylose Starches to Bridge the "Fiber Gap": Development, Structure, and Nutritional Functionality.

Compr Rev Food Sci Food Saf 2019 Mar 28;18(2):362-379. Epub 2019 Jan 28.

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

Although high-amylose starches are not a recent innovation, their popularity in recent years has been increasing due to their unique functional properties and enhanced nutritional values in food applications. While high-amylose maize, barley, and potato are commercially available, high-amylose variants of other main crops such as wheat and rice have once been developed more recently and will be available commercially in the near future. This review summarizes the development, structure, and nutritional functionality of high-amylose starches developed and reported so far. The range of biotechnological strategies utilized are reviewed, as are the consequent effects on structural properties at different length scales, as well as sensory aspects of foods containing high-amylose starch (HAS). This review identifies the molecular and microstructural features contributing to digestive enzyme resistance not only in native HAS but also in forms of relevance to food processing. During heat treatment, HAS tends to retain or form dense molecular structures that resist amylase degradation through the retention of the granular structure as well as helices (type-2 resistant starch [RS]), reassociation of glucan chains (type-3 RS), and formation of lipid-amylose complexes (type-5 RS). The review also identifies opportunities for food manufacturers and consumers to incorporate HAS in food products and diets for better nutritional outcomes.
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http://dx.doi.org/10.1111/1541-4337.12416DOI Listing
March 2019

Mechanism of binding interactions between young apple polyphenols and porcine pancreatic α-amylase.

Food Chem 2019 Jun 19;283:468-474. Epub 2019 Jan 19.

State Key Laboratory of Food Science & Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, PR China. Electronic address:

The binding interactions between young apple polyphenols and porcine pancreatic α-amylase were investigated through isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC) and molecular docking. The results obtained were compared with those obtained through inhibition kinetics and fluorescence quenching. It was found that binding of tannic acid, chlorogenic acid, caffeic acid and epicatechin with α-amylase is an exothermal process, with the binding constants in the order of tannic acid > chlorogenic acid > caffeic acid > epicatechin. This is consistent with the orders of reciprocal of competitive inhibition constant and fluorescence quenching constant. The binding energy obtained through molecular docking showed the same order, except for epicatechin. These results are consistent with the inhibition of α-amylase being caused by the binding of the polyphenols with the enzyme. In addition, from the fluorescence quenching and DSC data, total polyphenols, tannic acid, chlorogenic acid and caffeic acid were found to partially unfold the enzyme structure.
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http://dx.doi.org/10.1016/j.foodchem.2019.01.087DOI Listing
June 2019

Adsorption isotherm studies on the interaction between polyphenols and apple cell walls: Effects of variety, heating and drying.

Food Chem 2019 Jun 4;282:58-66. Epub 2019 Jan 4.

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, Brisbane, QLD 4072, Australia. Electronic address:

The adsorption capacity of principal phenolic compounds onto cell walls from three apple varieties was investigated. Isothermal adsorption modelled with Langmuir, Freundlich and Redlich-Peterson equations were carried out over a range of concentrations from 0.5 to 30 mM before and after cell walls were subjected to boiling, oven-drying or freeze-drying. The isotherm data were best fitted by the Langmuir model in all cases. Polyphenols selectively adsorbed onto cell walls with maximum binding capacities ranging from 140 to 580 µg/mg cell walls depending on surface charge. Increased pectin in apple cell walls caused a 129%-311% decrease in the adsorption of negatively charged polyphenols, presumably due to electrostatic repulsive forces. Boiling had limited effect on cell wall polysaccharides and polyphenol-cell wall interactions. However, more than twofold reduction in binding capacities of polyphenols was induced after drying by altering the structural (i.e. binding sites) and compositional (i.e. pectin degradation) characteristics of cell walls.
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http://dx.doi.org/10.1016/j.foodchem.2018.12.098DOI Listing
June 2019

Probing adhesion between nanoscale cellulose fibres using AFM lateral force spectroscopy: The effect of hemicelluloses on hydrogen bonding.

Carbohydr Polym 2019 Mar 18;208:97-107. Epub 2018 Dec 18.

Australian Research Council Centre of Excellence in Plant Cell Walls, The University of Queensland, Brisbane, QLD 4072, Australia; School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia. Electronic address:

Inter-fibre adhesion is a key contributing factor to the mechanical response and functionality of cellulose-based biomaterials. 'Dip-and-Drag' lateral force atomic force microscopy technique is used here to evaluate the influence of arabinoxylan and xyloglucan on interactions between nanoscale cellulose fibres within a hydrated network of bacterial cellulose. A cohesive zone model of the detachment event between two nano-fibres is used to interpret the experimental data and evaluate inter-fibre adhesion energy. The presence of xyloglucan or arabinoxylan is found to increase the adhesive energy by a factor of 4.3 and 1.3, respectively, which is consistent with these two hemicellulose polysaccharides having different specificity of hydrogen bonding with cellulose. Importantly, xyloglucan's ability to strengthen adhesion between cellulose nano-fibres supports emergent models of the primary plant cell walls (Park & Cosgrove, 2012b), which suggest that xyloglucan chains confined within cellulose-cellulose junctions play a key role in cell wall's mechanical response.
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http://dx.doi.org/10.1016/j.carbpol.2018.12.052DOI Listing
March 2019

Wall porosity in isolated cells from food plants: Implications for nutritional functionality.

Food Chem 2019 May 12;279:416-425. Epub 2018 Dec 12.

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:

Macronutrients in whole plant foods are enclosed inside cells. The metabolic response from these entrapped nutrients may depend on cell-wall porosity, by controlling the passage of digestive enzymes. As non-interacting size mimics of digestive enzymes, we investigated the diffusion of fluorescently-labelled probes across the walls of isolated plant cells from potato tuber, red kidney bean and banana. Diffusion properties of permeable probes, dextran (20-kDa and 70-kDa) and albumin, were quantified, using fluorescence recovery after photobleaching. The consistent reduction of diffusion rate in the presence of cell walls (around 40%) compared to free-diffusion rate was attributed to the limiting porosity of the wall matrix. A combination of the physical barrier effects demonstrated here and non-catalytic binding of enzymes to cell walls limits the hydrolysis of intracellular macronutrients. This and further understanding of the structural basis for the physical barrier properties would help to design foods from plant materials with enhanced nutrition.
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http://dx.doi.org/10.1016/j.foodchem.2018.12.024DOI Listing
May 2019

Molecular brewing: Molecular structural effects involved in barley malting and mashing.

Carbohydr Polym 2019 Feb 15;206:583-592. Epub 2018 Nov 15.

Joint International Research Laboratory of Agriculture and Agri-Product Safety, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu Province, China; The University of Queensland, Center for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia. Electronic address:

Ten barley samples containing varied protein contents were subject to malting followed by mashing to investigate molecular effects of both barley starch and starch- protein interactions on malting and mashing performances, and the underlying mechanism. Starch granular changes were examined using differential scanning calorimetry and scanning electron microscopy. The molecular fine structures of amylose and amylopectin from unmalted and malted grain were obtained using size-exclusion chromatography. The results showed that both amylose and amylopectin polymers were hydrolyzed at the same time during malting. Protein and amylose content in both unmalted and malted barley significant negatively correlated with fermentable sugar content after mashing. While protein content is currently the main criterion for choosing malting varieties, this study shows that information about starch molecular structure is also useful for determining the release of fermentable sugars, an important functional property. This provides brewers with some new methods to choose malting barley.
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http://dx.doi.org/10.1016/j.carbpol.2018.11.018DOI Listing
February 2019