Submitted to: Corn Utilization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 7, 2000
Publication Date: N/A
Technical Abstract: Zein, a predominant corn protein, is an excellent film former. Basic information is essential to design films with specific molecular structures, physical properties and morphological features. As one of the schemes for modification of zein, cross-linking was induced by addition of catalysts in the zein solution, 5 to 10% by weight in either 80% or 90% aqueous ethanol (w/w). However, the study of the reaction kinetics by turbidity measurement was complicated by the fact that zein aggregates in the absence of catalysts whereby the reaction products were confused with aggregates. To distinguish the cross-linking reaction product from aggregates, the aggregation behavior of zein in aqueous ethanol solution was studied at various conditions by measuring turbidity as a function of time. Laser light was passed through a stirred solution of zein and changes in the transmittance due to aggregation of zein were constantly monitored by a transducer. As variables for aggregation conditions, pH, centrifuge time, ionic strength of the medium, stirring speed, shaking time, etc. were considered. Aggregate formation could be visualized microscopically at various conditions. Next we cross-linked zein with combined catalysts; N-hydroxysuccinimide and 1-[3-dimethyl- aminopropyl]-3-ethyl-carbodiimide hydrochloride. The extent of cross- linking reaction was monitored with a UV spectrophotometer. The reaction took ca. 10 minutes for completion in our typical experimental condition. Cross-linked zein could be distinguished from unreacted zein after isolation by passage through a column of Sephadex LH-60. Cross-linked zein stripped of solvent generated a tough, transparent cellophane-like film, whereas, film of unreacted zein was transparent and somewhat brittle.