An improved soybean oil ester based epoxy resin and method of making the same is disclosed. A transesterification step is employed to liberate glycerol and to form new fatty acid esters with additional double bonds. The resulting fatty acid esters containing one or more double bonds are epoxidized by reacting with epoxidation reagent. The epoxidized esters serve as monomers in an epoxy resin system, which may be used to manufacture composite materials with improved mechanical properties as compared to materials obtained from epoxidized triglycerides. The soybean based epoxy resin may be used as low-cost and biocompatible coating materials for food and beverage cans.