Immune proteins in milk

Heating of both human and bovine milk has been shown to influences the healthy development of newborns , therefore heat label components are expected to cause this difference between breastfeeding and infant formala. Other research has also shown that unheated bovine milk may have the same protective effect as unheated breast milk, as many of the infections that are reduced by breastfeeding were also shown to be reduced in children being fed unheated bovine milk. Proteins are often relatively heat-labile, so the protective effect of milk may be caused by this class of heat-labile protein components. This protective effect may be directly through heat-labile immune active proteins in milk, but also formation of bioactive peptides during digestion of milk may be reduced due to protein aggregation during heating. The mechanisms that underlie the decrease in native milk proteins are not well understood. Denaturation and aggregation kinetics of single proteins has been studied in model system. However in the case of milk, these processes will be more complex. It has for example been shown that denatured proteins may aggregate with casein micelles. Also, due to the presence of the reducing sugar lactose, lactosylation of proteins will occur, which may enhance the aggregation of proteins during heating, leading to insoluble aggregates being formed. However, the extent of these modifications, especially in comparison to the above described modification lactosylation is yet unclear. Besides chemical modification, also release of bio-active peptides during digestion may be reduced after processing due to protein aggregation during heat processing Finally, it is unclear whether these changes to the milk proteins also render them inactive from a biological perspective. The aim of the project is thus to study the effect of heat processing on milk proteins in general and immune-active proteins in particular.

Aim
Characterize the heat damage to immune protein in bovine milk during heat processing
Determine which protein modifications happen at different heating intensity
Determine the release of peptides during digestion of heated milk proteins
Determine functionality of antibacterial milk proteins and of in-vitro digests in bacteriostatic assays.

Approach
filter-aided sample preparation and LC-MS/MS will be applied to analyze samples.