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A bio-plastic application for kafirin, the sorghum prolamin protein, but what is needed to enable its commercialisation
J. TAYLOR (1). (1) Univ of Pretoria, Pretoria Gauteng, South Africa

Environmentally friendly edible bio-plastic materials can be made from zein and kafirin, the prolamin storage proteins of maize and sorghum grain, respectively.  These natural materials show potential for use in the food industry as encapsulating agents for nutraceuticals and as coating materials to extend the shelf-life of fruit as described below.  Kafirin edible coatings variously containing functional additives propylene glycol (PG) and glucono-delta-lactone (GDL) were found to be effective at extending and maintaining the shelf-life quality of ‘Hass’ avocados for 21 days at ambient temperature. This was attributed to reduced respiration rate, and consequently reduced ethylene production of the coated fruit. Descriptive sensory analysis showed kafirin-PG+GDL coatings were most effective, extending the quality of the avocados 7 days beyond the untreated control. GDL, an acidulant widely used in the food industry appeared to act by improving kafirin solvation. Thus, kafirin- PG+GDL coatings are an effective method of extending eat ripe quality of climacteric fruit.  However, this and other promising prolamin bio-plastic products have not been commercialised.  High cost and inferior functional properties compared to synthetic polymer plastics are the primary reasons for this.  Improved economic viability should be possible by utilisation of prolamin-rich co-products from grain biofuel production, wet milling and brewing.  To enable bio-plastic materials with improved functionality to be produced, a greater understanding of how these very complex prolamins self-assemble into nanostructures, and then how these structures further assemble into various prolamin bio-plastic materials is needed and our research into this is presented here.  Such knowledge should enable scientists to manipulate and direct the process to improve functionality.

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