Food or cosmetic components are naturally hydrophobic or hydrophilic depending on their polarity. When those immiscible components are intent to be mixed together, an emulsion system is ideal for such practice. An emulsion system is thermodynamically unstable in nature. Any factors that can affect the emulsion stability once incurred; the emulsion would become instable and proceed to phase separation depending on the degree of influence and time. An emulsifier is a surface active agent that can minimize the surface tension between the dispersed phase and the continuous phase, and thereby stabilize an emulsion system. However, for various reasons, such as the characteristics of ingredients, formulation requirement, processing, sterilization etc., prepared foods have to face many environmental stresses that are unfavorable for an emulsion system, so do cosmetics. Therefore, developing a stable emulsion system is especially important for foods and cosmetics in such cases. Therefore, the aims of the study are to synthesize an emulsifier conjugated by sodium caseinate and chitosan via Maillard reaction, and to study the effect of the conjugate on the stability of oil-in-water system. Maillard reaction is affected by several factors: temperature, time, moisture content, pH, and reactants. The results showed that the temperature 60-80.degree.C and relative humidity 70-80% are favorable to the reaction. The suitable ratio of sodium caseinate to chitosan is one and the conjugate stabilized the o╱w emulsion better than the mixture of sodium caseinate and chitosan without reaction.
