Zeta-potential and particle size of functional additives based on goat milk proteins and Agaricus blazei Murill extracts.

Abstract

In recent years, the manufacturing of functional food has gained a lot of attention. The most recent studies indicate that bovine milk proteins are suitable carriers for a whole range of bioactive substances, mainly because of their micellar structure. The aim of our study was to examine the possibility of goat milk proteins (RM - raw skimmed milk and CN - casein fraction) to deliver A. blazei extracts (VA - hot water extract and GA - glucan extract) in order to use all the potential health benefits of this mushroom. Furthermore, the effect of thermal treatment (90⁰C, 10 min; TRM – thermally treated RM and TCN - thermally treated CN) on carrier properties was also evaluated. The mixture of different goat milk proteins and A. blazei extracts were prepared and zeta-potential and particle size distribution were determined by a laser light-scattering particle size analyzer, using distilled water as a dispersant. The best results were obtained with the RM and TRM mixtures. It can be concluded that changes in particle size and electric charge of the micellar surface occurring in goat milk after heating have a positive impact on carrier properties. The particle size of TRM mixtures increased by 13.3 to 15.7% compared to the size of TRM particles, whereas the zeta-potential of TRM/VA increased for 6.6% compared to that of TRM. TCNs did not follow this trend. The measurement of CNs particle size distribution showed the presence of significantly different sizes (coefficient of variation >30%), whereas the zeta-potential measurements were stable. These results imply that the measurements of zeta-potential cannot be interpreted without the particle size data.