This study has focused on the fabrication of five types of novel whey protein and pectin complexes with distinct functional properties which can be tailored to a particular application based on the different mechanism of assemblies of the two biopolymers. To achieve these objectives, the study was divided into three distinct phases.
The first phase covered specifically the making of the biopolymer complexes under different conditions such as pH, temperature, protein to pectin ratio or holding time and the structural properties such as the particle sizes (or hydrodynamic diameter) and zeta potentials. The five different WPP samples were made through the manipulation of heat and pH treatment of the biopolymers. Particle sizes of the WPP’s range from ≈0.7 to ≈2.7µm, whilst the complexes were found to be stable between pH 7 to 4, and from/below pH 2 but not stable between pH 3 and 2. With increasing protein concentration and fixed pectin concentration, the relationship with the particle size was linear for WPP01, WPP02 & WPP03 whilst particles were inversely proportional to biopolymer concentration for WPP04 and WPP05. Analysis by reduced SDS page revealed that most of the complexes were stabilised by disulphide bonds whilst SEM and SE-HPLC showed the presence and type of aggregates formed by the presence of bands at the stack gel and peaks and the void columns.
In the second phase, some functional properties of the samples were tested. Generally, WPP samples had improved functionality compared to the control samples (i.e. whey protein without pectin). The foaming ability reduced with the particle size increment whilst the foam stability was higher in samples without separately heated/denatured whey protein (WPP04 & WPP05). The emulsion ability and emulsion stability was also higher in samples with separately heated whey protein whilst the same trend was observed in the viscosities measurement. Aqueous solutions of WPP02 & WPP03 show shear thinning behaviour while other samples show Newtonian characteristics. The gel strength showed that the interaction between the protein and pectin in WPP02 & WPP03 is synergetic (i.e. harder gels) whilst in WPP01 it is antagonistic (i.e. softer gel). The solubility of the complexes reduced with increasing heat treatment on the samples whilst the reverse was the case for water holding capacity which increased with heat treatments.
The WPP particles were also used as a fat replacer in a model food system (mayonnaise), and at 50% fat replacement, whey protein-pectin complex particles have the potential to replace or mimic fat droplets and this may help reduce the cost of production and health risks associated with consumption of high-fat foods. Based on the structural experiments, postulated structures for the different types of particle were put forward. However, this is hypothetical and further work is required to determine with confidence how the biopolymers interact with each other under the different conditions of controlled heating and this will help to manipulate the structure better to achieve better functionality or a different product
