Mandelic Acid Incorporated Antimicrobial Soy Protein Film Fabricated by Solution Casting

Abstract

Soy protein exists in the market as soy flour (SF), soy protein concentrate (SPC), and soy protein isolate (SPI) and they differ in their protein contents. SPI contains about 90–92% of protein content followed by SPC having 70–72% protein. SPI films can be prepared by solution casting or compression molding method. In this work, different amounts of mandelic acid (1–5% wrt SPI) were added to glycerol plasticized SPI. The pH of the film-forming SPI suspension was maintained between 10 and 10.5. Mandelic acid incorporated SPI films were obtained after subjecting the solution casted SPI suspension on a glass plate for 24 h at 60 °C. The resulting SPI films with mandelic acid were subjected to antimicrobial, water uptake, transmittance, and tensile strength studies. The results indicated that with the increase in the concentration (till 4%) of mandelic acid, tensile strength and elongation at break increased from 6.5 to 7.5 MPa and 79 to 126%, respectively. The water uptake of the SPI films with mandelic acid decreased indicating less hydrophilicity of the resulting SPI film. Mandelic acid incorporated SPI film also showed antimicrobial nature that can be used for packaging.