Environmental Aspects of Proteinous Bioplastic

Abstract

During the processing of Novatein Thermoplastic Protein (NTP), volatile compounds are released which are odourous and potentially harmful. For NTP to be manufactured on a commercial scale the odour that currently arises during production must be minimised. Literature revealed that blood components are thermally unstable under oxidising conditions and in addition, the presence of iron in bloodmeal, may catalyse the formation of various odourous compounds. The objectives of this work were to establish an odour profile for bloodmeal and pre-extruded NTP (PNTP) and determine the effect of chemically treating bloodmeal on the resulting odour profile. In addition, the potential for NTP to be degraded by composting and effect of prolonged exposure to UV radiation was investigated. It was found that the initial odour of bloodmeal was caused by putrefaction during the storage of whole blood prior to drying as well as the formation of other, less odourous, volatile compounds derived from lipids and proteins during drying. The odour profile of pre-extruded NTP (PNTP) was found to change after chemical treatment of bloodmeal. Chemical treatments successfully minimised or changed the odour of the bloodmeal. Peracetic acid treatment successfully removed the characteristic bloodmeal odour resulting in decolourised bloodmeal with a mild vinegar odour. In general, removing odour from the PNTP could not be achieved without the addition of 10-20 wt% activated carbon or greater than 20 wt% natural zeolite. Additionally, for NTP to be marketed as biodegradable as well as bio-derived plastic, it must be shown to degrade in the environment at a rate comparable with cellulose. NTP was found to undergo substantial deterioration and polymer degradation within 12 weeks of composting, for plasticised samples up to 47 % dry mass loss was observed. However, exposure to 12 weeks of ultra-violet radiation, lead to embrittlement of the plastic with very little polymer degradation occurring.