Processing and stability of infant formula-based emulsions as affected by emulsifier type

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Drapala, Kamil P.
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University College Cork
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Infant formulae (IF), which are emulsion-based nutritional products, are prone to destabilisation during processing and on storage due to their inherent thermodynamic instability. Currently, IF emulsions are stabilised mainly by innate protein-based emulsifiers that are adapted (e.g., source, profile, peptide chain length) to cater for specific nutritional requirements, and often require the inclusion of non-protein emulsifiers (e.g., polar lipids) to improve stability of these products. This thesis represents new and innovative research on the properties and performance of selected innate and added emulsifiers in IF products (i.e., whey protein isolate, WPI; whey protein hydrolysate, WPH; phospholipids and citric acid esters of glycerides) and more novel emulsifiers formed by Maillard-induced conjugation of WPH with maltodextrin. This research focused predominantly on the surface activity of emulsifiers, their ability to form emulsions and to subsequently stabilise them against shear-, heat- and storageinduced changes. Conditions used to test the stabilisation properties included refrigerated storage (14 d at 4°C), thermal processing (75-100°C × 15 min), accelerated shelf-life testing and spray-drying. Studies on the stability of model IF emulsions showed that prevalence of detrimental changes, such as competitive displacement of emulsifiers from interfaces of oil globules and their coalescence during storage, and protein/peptide-mediated aggregation of oil globules during heating, were significantly influenced by the emulsifiers used to form these emulsions. In a similar way, the emulsifiers influenced spray-drying properties (e.g., cohesive interactions) of model IF systems by contributing to different surface composition of resulting powders. The findings presented in this thesis constitute a significant advancement in research on mechanisms of stabilisation of IF emulsions provided by a potent steric barrier on oil globules using conjugated proteins/peptides; this work adds to the rapidly expanding research on interfacial composition and structural organisation of oil globules in IF products and opens up new possibilities for designing novel emulsion-based nutritional products.
Infant formula , Hydrolysed proteins , Conjugated proteins , Emulsion stability , Emulsifiers , Microscopy
Drapala, K. P. 2017. Processing and stability of infant formula-based emulsions as affected by emulsifier type. PhD Thesis, University College Cork.