Date of Award


Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy


Biological Sciences

First Advisor

Dr Michael Callanan


Breastfeeding is recognised as the gold standard for feeding newborns and infants. However, infants who cannot be breast-fed or for whom breast milk is not available, can be fed with bovine infant milk formula (IMF) as a substitute. Researchers and producers of IMF strive to continually improve or “humanise” the composition and functionality of IMF. During production of IMF it must undergo several heat treatment steps, e.g. heat-sterilisation or spray-drying, in order to provide a safe product to the infant. These heat treatments denature the globular whey proteins in IMF. In contrast, breast milk is by its nature unheated, so all proteins are in their native form. As a consequence of whey protein denaturation, IMF and breast milk display different digestive and bioactive properties. The purpose of this thesis was to investigate the effects of membrane filtration during IMF processing on maintaining the native structure of whey proteins, and their effect on the gastro-intestinal behaviour and bioactivity of IMF compared with conventional heat treatment. Both lab and pilot-scale manufacturing of membrane filtrated IMF (MEM-IMF) were validated in the studies. The MEM-IMF had markedly increased levels of native whey proteins and water-soluble proteins in the final powders compared to conventional heat treated IMF (HT-IMF). The increase in native whey proteins in MEM-IMF altered the gastrointestinal digestion kinetics and enabled faster protein hydrolysis in both in vitro semi-dynamic digestion and in an in vivo piglet model. In vitro cell models revealed that ex vivo serum collected from MEM-IMF fed piglets promoted adipocyte proliferation and differentiation, in comparison with HT-IMF fed. This thesis demonstrated that MEM-IMF and HT-IMF exhibit favourable digestive behaviour and bioactivities due to the different levels of native whey proteins. The outcomes of this work provides valuable insights into the scaling up MEM-IMF to industrial scale. It also presents the results of state-of-the-art bioavailability assays for IMF by using both an infant in vitro semi-dynamic digestion method and in vivo piglet digestion combined with ex vivo-in vitro serum-cell model.

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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