Browsing by Author "Conn, CE"

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    Application of small angle scattering (SAS) in structural characterisation of casein and casein-based products during digestion
    (Elsevier, 2023-07) Bayrak, M; Mata, JP; Conn, CE; Floury, J; Logan, A
    In recent years, small and ultra-small angle scattering techniques, collectively known as small angle scattering (SAS) have been used to study various food structures during the digestion process. These techniques play an important role in structural characterisation due to the non-destructive nature (especially when using neutrons), various in situ capabilities and a large length scale (of 1 nm to ∼20 μm) they cover. The application of these techniques in the structural characterisation of dairy products has expanded significantly in recent years. Casein, a major dairy protein, forms the basis of a wide range of gel structures at different length scales. These gel structures have been extensively researched utilising scattering techniques to obtain structural information at the nano and micron scale that complements electron and confocal microscopy. Especially, neutrons have provided opportunity to study these gels in their natural environment by using various in situ options. One such example is understanding changes in casein gel structures during digestion in the gastrointestinal tract, which is essential for designing personalised food structures for a wide range of food-related diseases and improve health outcomes. In this review, we present an overview of casein gels investigated using small angle and ultra-small angle scattering techniques. We also reviewed their digestion using newly built setups recently employed in various research. To gain a greater understanding of micro and nano-scale structural changes during digestion, such as the effect of digestive juices and mechanical breakdown on structure, new setups for semi-solid food materials are needed to be optimised. © 2023 Elsevier Ltd
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    Investigating casein gel structure during gastric digestion using ultra-small and small-angle neutron scattering
    (Elsevier, 2021-07-15) Bayrak, M; Mata, JP; Ranynes, JK; Greaves, M; White, JF; Conn, CE; Floury, J; Logan, A
    An understanding of the structural factors that affect food digestion kinetics is important for establishing the relationship between their structure and function. To assess the effects of structure on mechanical breakdown and digestibility by pepsin enzyme during gastric digestion, casein gels with an identical composition, but differing by the coagulation mode, were characterized and submitted to simulated in vitro gastric digestion. Rennet-induced (RG) and transglutaminase-induced acid (TG) gels were made and digested in two different solvents - H2O and D2O. The structural changes were assessed during simulated gastric digestion by ultra-small (USANS) and small angle neutron scattering (SANS). The different structures of RG and TG reveal distinctive breakdown behaviours over a hierarchy of length scales (nano- to micro). Different functional properties of casein gels, such as gel strength, elasticity, brittleness, resistance to shear and sensitivity to the acidic environment of gastric phase, obtained by scanning (SEM) and transmission electron microscopy (TEM), contributed to the differences in gel disintegration and gastric digestibility. Despite the higher gel strength and thus higher number of larger gel particles entering the gastric phase following mastication, the porous microstructure of RG provided a larger surface area and thus higher simulated digestibility compared to TG. The effect of acidification is clearer with RG, wherein the local compactness of each gel consequently drives its porosity and pepsin accessibility. On the other hand, pepsin has a limited diffusion capability inside the TG structure due to its fine stranded network; however, the brittle structure of TG is more affected by mechanical shear during the gastric phase, causing particle erosion. In a similar manner, gels made and digested in D2O had a higher level of mechanical breakdown due to their brittle structure: initially led by the fracturing of particles with a larger surface area, this increases the levels of solubilised protein, small peptides and amino acids. Here, we report the first USANS and SANS study to monitor structural changes of a casein gel both in H2O and D2O during simulated in vitro gastric digestion. We show that solvent (H2O and D2O) and gel type (RG and TG) affects digestion components: mechanical shear, enzymatic hydrolysis and the effect of acidification. © 2021 The Authors. Published by Elsevier Inc.
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    Real-time monitoring of casein gel microstructure during simulated gastric digestion monitored by small-angle neutron scattering
    (Elsevier, 2023-11) Bayrak, M; Whitten, AE; Mata, JP; Conn, CE; Floury, J; Logan, M
    The evolving structure of protein-based foods during the digestion process is critical to the release of nutrients. However, traditional in vitro monitoring of the gel micro- and nano-structure during digestion involves analysing sample aliquots taken at different digestion time periods. This can pose issues for some gels, such as casein-based gels, as they are sensitive to sample manipulation and environmental changes. Herein, a newly developed flow setup was utilised to monitor (at the micro- and nano-length scales) the gel protein network of rennet-induced (RG) and transglutaminase-induced acid gels (TG) in situ and in real-time during simulated gastric digestion using ultra-small and small-angle neutron scattering (USANS and SANS). The proteolysis kinetics of the gels were investigated at two different pepsin enzyme concentrations (2000 and 8000 U mL-1) and in two different solvent environments (H2O and D2O). Results indicate that the flowing in situ system had a greater effect on the microstructural breakdown of TG relative to the acid-sensitive RG, compared to the traditional static method. This is the first in situ digestion study observing the structural changes of large protein gel particles with USANS or SANS in real-time. Our findings advance the understanding of the kinetics of casein gel disintegration under simulated conditions of gastric digestion relating to pepsin enzyme concentration and solvent environment, and critically, the utilisation of a new in situ and real-time setup for neutron studies. © 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.