Soymilk is a highly nutritious beverage, closely resembles to dairy milk respect to its physical properties. Recently, soymilk has been used as an important replacer for milk particularly for lactose intolerant or casein allergic people. In spite of its valuable nutritional content,soymilk contains less calcium than cow’s milk. The aim of this study was to fortification of soymilk with tri-calcium phosphate (TCP) salt in order to increase calcium content to 500 mgCa/serving as recommended daily allowance (RDA) was provided.Fortification of soymilk with calcium may lead to calcium-protein interaction as well as protein coagulation.In order to inhibit calcium-protein interaction and improve the soymilk stability, different concentrations i.e. 0, 1, 1.5, 2, 2.5 and 3 % of potassium citrate were added to soymilk samples as a metal chelating agent. The physicochemical properties of soymilk including pH, phase separation, sedimentation, viscosity, conductivity and color parameters (L, a, b and ?E) were assayed during 10 days of storage and resulting data was analyzed by completely randomized factorial design using SAS software. Adding chelating agent to soymilk may cause undesirable aftertaste and side effects on body. Thus, in order to solve this problem and also to enhance bioavailability during digestion in gut, calcium was microencapsulated. Calcium entrapment was performed using water-in-oil-in-water (W/O/W) double emulsion method and complex coacervates were formed by means of gelatin-agar interaction. W/O/W emulsion was prepared by a two step method: first, TCP solution was homogenized (14000 rpm, 1 min) with canola oil containing lipophilic emulsifier, glycerol monoesterate, in an ice bath to produce W/O primary emulsion. Second, gelatin and agar solution were heated to 50 , mixed together and cooled to 35 . W/O primary emulsion was homogenized with gelatin-agar solution at 8000 rpm for 2 min.After that, the pH was immediately reduced to 4.2 causing coacervate formation. Resulting microcapsules were freeze dried and milled. Optimization of 20 formulations was performed using mixture design with four components including gelatin, agar, W/O emulsion or oil phase and water using Design-Expert software. Special cubic and quadratic models were the best for modeling of microencapsulation efficiency (ME) and payload, respectively. Results showed that ME was ranged 58.43-92.41 % and payload was ranged 3.34-5.62 %, respectively. Droplet size was increased by increase of biopolymer concentration. Calcium release rate was slowed down by increasing of oil phase and biopolymer concentrations. Based on microcapsule examinations, the powder of optimum formulation was added to soymilk so that the calcium content equaled to direct calcium addition to soymilk i.e. 500 mg/serving. Microcapsule-fortified soymilk was improved with previous soymilk samples regarding to physicochemical and organeloptic properties, proximate analysis and microbial load.
