Insignificance of lactose impurities on generation and structural characteristics of thermally stabilised whey protein-pectin complexes

We studied the impact of lactose impurities (0, 130, 150 mm) on micro- and macro-structural characteristics of thermally stabilised whey protein-pectin complexes (WPPC) by varying biopolymer concentration [chigh = 5.0% whey protein isolate (WPI) + 1.0% pectin; cmed = 2.75% WPI + 0.55% pectin; clow = 0.5% WPI + 0.1% pectin], shear rate (0, 150, 500 s−1) and scale (lab/pilot plant). We demonstrated that ≤150 mm lactose had no significant effect on the microstructure of WPPC, as investigated by fluorescence spectroscopy and browning measurements. Unfolding of β-lactoglobulin within WPPC depended on the biopolymer concentration, being strongest at chigh. Measured browning was attributed to reactions between whey proteins and neutral sugars in pectin side chains. Particle size was unaffected by lactose, but showed an increase with biopolymer concentration and a decrease with shear rate. Thus, WPPC can likely be generated using whey powders with lactose impurities or other protein sources of lower purity.