Properties of epsilon-polylysine•HCl/high-methoxyl pectin polyelectrolyte complexes and their commercial application

The objectives of this study were to characterize the physicochemical properties and evaluate the antimicrobial capacity of polyelectrolyte complexes (PECs) consisting of cationic epsilon-polylysine center dot HCl (epsilon center dot PL center dot HCl) and anionic high-methoxyl pectin (HMP). The physicochemical properties were analysed by microelectrophoresis (zeta-potentials), mean diameter (Z-average), differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Experimental results indicated that PECs have different physicochemical properties or behaviour dependent on epsilon center dot PL center dot HCl/HMP mass ratio and epsilon center dot PL center dot HCl concentration. The antimicrobial activity was tested by minimal inhibitory concentration (MIC), which showed that the PECs had effective antimicrobial activity. Finally, this study found that using an appropriate proportion of PECs could not only avoid the formation of undesirable precipitates resulting from the interaction between epsilon center dot PL center dot HCl and anionic components within the soymilk systems, but also could extend their shelf-life. Practical applications epsilon-polylysine and its derivatives would interact with anionic components within foods and beverages through ionic adsorption resulting in forming undesirable precipitates, which will cause the decrease in its antimicrobial activity and the loss of food nutrients. In this study, HMP with epsilon center dot PL center dot HCl were used to form polyelectrolyte complexes as antimicrobial delivery systems and further reveal their physicochemical and antimicrobial properties. They could be satisfactorily applied in soymilk systems without sacrificing effective antimicrobial activity of epsilon center dot PL center dot HCl as well as avoiding undesirable precipitation. This information is expected to practical into protein-containing beverage systems to extend their shelf-life.