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Impact of Thiocyanate Salts on Physical, Thermal, and Rheological Properties of Zein Films

¹Plant Polymer Research Unit, National Center for Agricultural Utilization Research, USDA–Agricultural Research Service, 1815 N. University St., Peoria, IL 61604. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA to the exclusion of others that may also be suitable. USDA is an equal opportunity provider and employer. ²Corresponding author. Phone: (309) 681-6337. Fax: (309) 681-6691. E-mail: gordon.selling@ars.usda.gov ³USDA–Agricultural Research Service CGAHR, 1515 College Ave., Manhattan, KS 66502.

A new class of zein additives was investigated, thiocyanate salts. Ammonium, potassium, guanidine (GTC), and magnesium thiocyanate salts were added to solutions of zein in with various amounts of tri(ethylene glycol) (TEG), cast as films, and then tested to determine the impact that each salt had on properties. The presence of these salts affected solution rheology and intrinsic viscosity, demonstrating that the salts interacted with the protein. It was found that these salts acted as plasticizers, as they lowered the glass transition temperature of zein when evaluated with differential scanning calorimetry. In zein films in which TEG was present, these salts increased elongation and reduced tensile strength. However, unlike traditional plasticizers (such as TEG), when the salts were used as the only additive, elongation was not increased and tensile strength was not decreased. Of the salts tested, GTC in combination with TEG was found to increase elongation the most. The impact of salts on elongation was greatly affected by the relative humidity in which the samples were stored.