Submitted to: Journal of Biobased Materials and Bioenergy
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2010
Publication Date: 3/1/2011
Citation: Mukhopadhyay, S., Onwulata, C.I., Yadav, M.P., Thomas-Gahring, A.E., Tunick, M.H. 2011. Thermophysical properties of starch and whey protein composite prepared in presence of organic acid and esters. Journal of Biobased Materials and Bioenergy. 5:10-8. Interpretive Summary: We did this work because there is a growing demand for biodegradable plastic material for our every day need such as food packaging film, water bottles, trash bags etc. Synthetic plastics are not biodegradable and cause environmental pollution. So we mixed renewable agricultural commodities such as corn starch and milk whey protein in presence of organic acids and esters at high temperature in a machine called ‘Extruder’ to form a new biodegradable material called composite which was molded under high pressure and temperature. Our result explain that organic acid esters drastically improve the starch-protein composite property to make it behave like a plastic. This finding has commercial potential since it provides a way to cut back on our dependence on synthetic plastic.
Technical Abstract: Previously, we prepared starch and protein composite by reactive mixing in presence of various organic acids and found that use of these acid esters resulted in composites with good mechanical properties. In this study, concentration (% w/w) of acid citrates in the starch-protein composites were varied ranging from 5, 15 and 30. The optimum concentration of the acid citrates when mechanical properties of the composites were the best was 15% (w/w). The equilibrium moisture content of composites reduced in presence of acid citrates. TMC influenced maximum reduction in moisture from 33.34% to 12.70%. Peak melt for TMC based composite increased by 46.1 deg C and melt enthalpy decreased by 134 J/g at 15 wt%. Peak melt for TEC based composites increased by 10 deg C and melt enthalpy decreased by 65.1 J/g at 15 wt%. Presence of acid esters decreased the glass transition temperature except for TMC. TEC at a level of 15%, depressed the glass transition temperature by about 9.5C for the composite indicating a 33% decrease. Compared to control, storage modulus increased by 86 MPa for TMC based composite and by 230.2 MPa for TEC based composite at optimum concentration indicating more than 150% improvement in mechanical strength in the presence of TEC. Adding acid citrates to starch-protein composite increased tensile modulus, elongation at peak, peak load, break load and elongation at break. Tensile strength increased by 700 % due to TMC and by 267 % due to TEC. TEC influenced higher elongation (32.8%) at peak load than TMC (18.2%).