Processes have been developed to incorporate cornstarch into plastics with the intent of increasing the rate of plastic biodegradation. The effect of starch-degrading enzymes on food-grade polyethylene film that contained 6% cornstarch (CSPE) was examined. Control polyethylene film with no added starch, CSPE and laboratory grade soluble starch were treated with α-amylase, β-amylase, or amyloglucosidase. Samples were removed periodically and were subjected to the Nelson-Somogyi method for the determination of reducing sugar content. Treatment with α-amylase and β-amylase released over 30% of the soluble starch as glucose, while less than 1 % of the starch in CSPE was released. Amyloglucosidase activity released up to 50% of the soluble starch as reducing sugar. However, less than 4% of the CSPE starch was liberated. Image analysis of iodine-stained films showed that enzymatic treatment did not remove surface granules. These results indicated that breakdown of CSPE by starch degrading enzymes was limited.

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Author notes

Published as paper No,. 19748 of the contribution series of the Minnesota Agricultural Experiment Station based on research conducted under Project 18-56 supported by Hatch Funds and funds from the Agricultural Utilization Research Institute, Crookston, MN.