Emulsification and Emulsion Stabilising Properties of Fragment Plant Proteins

This PhD project investigates the possibility of fragmented plant proteins as suitable and novel food-grade emulsifiers using a combination of theoretical and experimental approaches. Two innovative fast screening methods (coarse-graining and moving average methods) have been developed for selecting suitable fragments from intact proteins. A di-block-like fragment was found according to the primary structure of β-conglycinin. Then self-consistent field calculations (SCFC) were carried out to verify further the emulsification capacity of the fragment selected by fast screening methods. In the experiment, soy protein isolate (SPI) was hydrolysed by pepsin under optimal (pH 2.1) and non-optimal (pH 4.7) conditions and the surface activity and emulsion stabilising capacity of the resultant peptides were measured and modelled via SCFC. Hydrolysis at pH 2.1 and 4.7 resulted in a considerable increase in measured surface activity compared to the native (non-hydrolysed) SPI, but the hydrolysate from pH 2.1 was not a good emulsion stabiliser compared to the hydrolysate (particularly a fraction Mw > 10 kDa) at pH 4.7. Furthermore, peptide analysis of the latter (pH 4.7) suggested it was dominated by a fragment of one of the major soy proteins, β-conglycinin of Mw ≈ 25 kDa. SCFC calculations confirmed that this peptide should be an excellent stabiliser.