We investigated the influence of the components in the coffee extract solution on the emulsion stability. In many components, we noticed the organic acid and caffeine were representative of the electrolyte and non-electrolyte, respectively. These components were added to the model milk solution. In the presence of the emulsifier, milk separation was observed above the 0.7 wt% concentration of trisodium citrate as the electrolyte (Table 5). Without an emulsifier and with caffeine as the non-electrolyte, the milk separation was not observed. There are two main effects of citrate addition: pH and ionic strength. When we used the trisodium citrate as an example of electrolyte, ionic strength increased but pH did not lower (Table 5).