Browsing by Author "Sims IM"

Now showing 1 - 3 of 3
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    A protocol combining breath testing and ex vivo fermentations to study the human gut microbiome
    (Elsevier Inc, 2021-03-19) Payling L; Roy NC; Fraser K; Loveday SM; Sims IM; Janssen PH; Hill SJ; Raymond LG; McNabb WC
    This protocol describes the application of breath testing and ex vivo fermentations to study the association between breath methane and the composition and functionality of the gut microbiome. The protocol provides a useful systems biology approach for studying the gut microbiome in humans, which combines standardized methods in human breath testing and fecal sampling. The model described is accessible and easy to repeat, but its relative simplicity means that it can deviate from human physiological conditions.
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    Does harvesting age matter? Changes in structure and rheology of a shear-thickening polysaccharide from Cyathea medullaris as a function of age
    (Elsevier Ltd, 2024-04-01) Bisht A; Goh KKT; Sims IM; Edwards PJB; Matia-Merino L
    A shear-thickening polysaccharide from the New Zealand Black tree fern (Cyathea medullaris, commonly known as mamaku) extracted from different age fronds (stage 1: young, stage 2: fully grown and stage 3: old) was characterised in terms of structure and rheological properties. Constituent sugar analysis and 1H and 13C NMR revealed a repeating backbone of −4)-β-D-GlcpA-(1 → 2)-α-D-Manp-(1→, for all mamaku polysaccharide (MP) samples from different age fronds without any alterations in molecular structure. However, the molecular weight (Mw) was reduced with increasing age, from ~4.1 × 106 to ~2.1 × 106 Da from stage 1 to stage 3, respectively. This decrease in Mw (and size) consequently reduced the shear viscosity (ηs-Stage 1 > ηs-Stage 2 > ηs-Stage 3). However, the extent of shear-thickening and uniaxial extensional viscosity of MP stage 2 was greater than MP stage 1, which was attributed to a greater intermolecular interaction occurring in the former. Shear-thickening behaviour was not observed in MP stage 3.
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    Shear and temperature sensitivity of a shear-thickening biopolymer from the New Zealand black tree fern
    (Elsevier Ltd, 2023-12-01) Bisht A; Goh KKT; Sims IM; Edwards PJB; Matia-Merino L
    Mamaku polysaccharide (MP) is a water-soluble shear-thickening biopolymer that has shown potential to be used in the design of novel food products targeting satiety management and weight loss. During the processing of MP at industrial scale, the polymer may be exposed to high temperature and shear, which could affect its rheological behaviour. Thus, herein we subjected extracted MP to high shear (between 1000–8000 rpm at various times, using a lab-scale high-shear mixer) and temperature treatment (between 65 and 115 °C, for 30 min) and investigated the changes in molecular structure and rheological properties. The temperature treatment disintegrated the backbone of MP into smaller fragments (molecular weight-Mw, reduced from ∼3.9 × 106 Da with no heat, to ∼0.6 × 106 Da at 115 °C), which caused a reduction in viscosity and in the extent of shear-thickening as well as an increase in the damping factor (Gʹʹ/Gʹ). Similar rheological trends were observed post-shear treatment, however, there was no evidence of depolymerisation, with the Mw, constituent sugar composition and NMR spectra (1H and 13C) being unaffected. It is suggested that the changes in rheological behaviour after shear treatment could be due to changes in the re-arrangement of MP molecules, which led to a compact and folded structure due to increased intra-molecular interactions. The results, therefore, indicate that modification of MP molecules during the industrial process such as shearing and heating should be considered as it may adversely affect the rheological properties of the product where MP is incorporated and the expected physiological benefits in the gastrointestinal tract.