Browsing by Author "Welman A"

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    Heat-set gelation of milk- and fermentation-derived β-lactoglobulin variants
    (Elsevier Ltd, 2025-08) Pan Z; Kornet R; Hewitt S; Welman A; Hill JP; Wubbolts M; Mitchell S; McNabb WC; Ye A; Acevedo-Fani A; Anema SG
    Milk-derived β-lactoglobulin (mβ-LG) and fermentation-derived β-lactoglobulin (fβ-LG) may slightly differ in their amino acid sequences. This study aims to investigate the heat-set gelling behaviour of mβ-LG (variants A, B, and C) and fβ-LG A variants. Differential scanning calorimetry indicated similar denaturation temperatures for mβ-LG A and fβ-LG A (∼75 °C), with mβ-LG C highest (∼81 °C) and mβ-LG B intermediate (∼78 °C). All fβ-LG A formed translucent gels with a fine-stranded structure, whereas mβ-LG A, B, and C formed opaque gels with a coarse particulate structure. fβ-LG A exhibited delayed gelation onset and lower gel stiffness compared to mβ-LG A. Among mβ-LG's, mβ-LG A showed the highest gel stiffness, followed by mβ-LG B and then mβ-LG C. Rheological analysis showed that fβ-LG A gels were more elastic and ductile compared to mβ-LG A gels, indicated by smaller tan δ values and delayed increases in energy dissipation ratio at higher strain amplitude; mβ-LG B and mβ-LG C gels were less elastic but more ductile compared to mβ-LG A gels. The more elastic and ductile nature of fβ-LG A gels indicates their potential for applications requiring these specific textural properties. By selecting mβ-LG variants from milk and/or utilizing precision fermentation to engineer additional differences, it is possible to tailor the gelation characteristics of β-LG to meet specific functional requirements.
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    Impact of protectant uptake on the shelf-life of dried Lacticaseibacillus rhamnosus
    (Elsevier, 2022-01) Priour S; Welman A; Singh H; Ellis A
    To improve the survival of dried probiotics, it is advised to expose the bacteria to protectants prior to processing, allowing equilibration of internal solutes. However, optimal conditions for this exposure remain unclear. This study examined solute uptake by Lacticaseibacillus rhamnosus HN001 (formally known as Lactobacillus rhamnosus HN001) at 4 °C and 20 °C, over exposure times of 0–240 min. The cells were exposed to hyperosmotic solutions of glucose and sucrose, two potential protective sugars, which are metabolisable and have different molecular weights. Sugar uptake was analysed through HPLC, while the impact on cell viability after freeze-drying was examined at 30 °C and 40 °C. The interactions between cell biomolecules and sugars were examined using Nano DSC. Results showed that the sugars were rapidly taken up by the cells, independent of temperature. At 20 °C, glucose was readily metabolised, eventually resulting in loss of cell viability during storage. Conversely, the Nano DSC study revealed interactions between the cells and sucrose, potentially providing some explanation as to the stability of the cells. In conclusion, sugar type and exposure temperature were shown to exert a significant effect on the viability of Lacticaseibacillus rhamnosus. Nano DSC is a promising technique to understand the protectant and cells’ interactions.