Production of Cornstarch-poly (Lactic Acid) Extrudates with High Expansion and Low Water Solubility

Abstract

Maximum expansion ratio and minimum bulk density and water solubility of cornstarch-poly (lactic acid) (PLA) extrudates were predicted using response surface methodology. An increase in temperature decreased the expansion ratio markedly at low moisture content (around 12%). Maximum expansion ratio was 30.2 at 110°C barrel temperature, with 12% moisture content and 19.4% PLA content. Although bulk density of the extrudates was inversely related to the expansion ratio (r = - 0.652), the conditions for minimum bulk density were different. Minimum bulk density was 0.011 (g/cm3) at 170°C barrel temperature, with 15% moisture content and 20.5% PLA content. Water solubility was significantly dependent on PLA contents, minimum water solubility was 24.3% at 110°C barrel temperature, with 12.1% moisture content and 22.8% PLA content. The conditions for closest responses to the maximum or minimum values were predicted using MINITAB response optimizer software. Thirty point one of the expansion ratio, 0.020 (g/cm3) of the bulk density and 24.7% of water solubility were obtained at 110°C barrel temperature, 12% moisture contents and 21.9% PLA contents. For biodegradability of starch-PLA extrudates, an increase in PLA content decreased the biodegradability rate significantly.