The increasing demand for environmentally friendly/biodegradable plastics has driven research to explore the use of agriculturally-derived materials in biocomposites. Dairy proteins have functional properties similar to many plastics and may be suitable replacements for plastics in biocomposites; however, they are not as strong. We blended whey protein isolates and casein (40%), corn starch (30%), glycerol (10%), cellulose (5%), and water (15%) with Acetic Acid (AA) in varying ratios to form the dairy biocomposite. The blend was mixed with roller blades in a torque rheometer for 40 min at initial temperature of 70 °C. After mixing, the biocomposite paste was molded into ASTM stripes at 121 °C for 30 min using a Carver press. The results showed that as the ratio of AA increased, the storage modulus of the biocomposite increased to an optimum (862.1 MPa) at 3.75% AA compared to the control (676.0 MPa) with 0% AA. This result shows that reactively mixing dairy biocomposites with AA improves mechanical strength.