Odorous Compounds in Bioplastics Derived from Bloodmeal

During the processing of bloodmeal-based thermoplastics (BMT), volatile compounds are released which are odorous and unpleasant. Literature searches revealed that blood components are thermally unstable under oxidising conditions and the presence of iron in bloodmeal (BM) may catalyse the formation of various odorous compounds. The objective of this work was to establish an odour profile for BM as well as BMT prior to extrusion and to determine the effect of oxidative treatment on the resulting odour profile. A comparison of the volatile compounds arising from using BM with those arising from using red blood cells (RB) was carried out using headspace-solid phase micro-extraction–gas chromatography–mass spectrometry (HS-SPME–GC/MS). A total of 23 compounds were identified, 4 of which were products of putrefaction also identified in RB subjected to putrefactive degradation; these were phenol, 4-methyl phenol, indole and methyl indole. In addition, several aldehydes and ketones were identified in BM and RB and may result from thermal, microbiological or auto-oxidative deterioration of the lipids and proteins present in blood during BM manufacture. Oxidative treatment of BM removed some of the compounds that were generated by putrefaction and thermal degradation. Treatment led to an improvement in the perceived odour type and intensity of BM, however, upon conversion to BMT the perceived odour became significantly worse. This malodour was able to be mitigated by the addition of 10–20 wt% activated carbon or greater than 20 wt% natural zeolite, however some malodour reoccurred after storage.