Oxidative stability of FAME prepared from oxidatively degraded rapeseed oils

The present paper contains induction period (IP) values obtained from Rancimat and peroxide value (PV) tests of oxidatively degraded rapeseed oils. Methyl esters of fatty acids (FAME), prepared freshly from these oxidatively degraded oils and two months after the preparation are simultaneously evaluated for the samples kept in open transparent bottles at laboratory temperature, without agitation during the storage, and samples both with and without added antioxidant. The results lead to a conclusion that even oils with PV at the level of some tens mmol O/kg can be used for the preparation of FAME with low PV (3.4–7.8 mmol O/kg) and IP values ranging from 6 to 10 h after antioxidant addition. Stabilization with the antioxidant butylhydroxytoluene (0.1 wt.%) is effective, IP conforms to standard at least for 2 months after the stabilization. Strongly oxidatively degraded oils with PV reaching several hundreds of mmol O/kg are not suitable for preparation of FAME as an alternative of diesel fuel. Such FAME may have problems with ester content, insufficient IP as well as with conversion degree. IR spectroscopy in the MID-region (MID-IR spectroscopy, 2600–3200 nm) may be useful in the prediction of the oxidative stability of FAME derived from the oxidatively degraded oils.