Formulation of peppermint oil nanoemulsion using conjugates of whey proteins with maltodextrin and its characterization

Whey protein-maltodextrin conjugate is used as emulsifier and stabilizer to prepare peppermint (Mentha piperita L.) oil (PO) nanoemulsion. The mean particle size, zeta potential and poly dispersity index (PDI) of stable PO nanoemulsion (5% oil+8% conjugate+0.5% Tween 80) was 144.8±5.32 nm, -24.40±0.42 mV and 0.217±0.05 respectively and this formulation was not unstable to food processing conditions like pH 3.0 to pH 7.0, heat treatments and ionic strength 0.1 M to 1.0 M. The emulsion was stable at 25°C for 15 days and its particle size is 332.2±4.66 nm at 15th day of storage. Agar well diffusion method is used to assess the antimicrobial efficacy of PO (5%) dissolved in dimethyl sulphoxide (DMSO) and 5% PO nanoemulsion against microorganisms like E. coli ATCC 25922, B. cereus ATCC 14459, Salmonella typhi NCDC 6017 and E. faecalis NCDC 115. The formulation prepared in the present study will have the application in preservation of various foods against spoilage microorganisms.