In this study the efficiency of horseradish Amorica rusticana leaf, and Levisticum officinale lovage leaf and stem extracts for the stabilisation of rapeseed oil during storage was evaluated. Plant extracts were added to unrefined rapeseed oil in a concentration of 1% by weight, which was chosen based on the results of previous experiments studying the possibilities of the addition of different concentrations of plant extracts for extending the shelf life of the oil. As a control a rapeseed oil sample without extracts was analysed, and for comparison butylated hydroxytoluene (BHT) in the maximum allowed concentration was added to the oil. The efficiency of the extracts in oil was tested in the dark and in the light/dark cycles (day/night regime). For all samples the peroxide value, acid value and DPPH scavenging activity were determined. The oil samples with the added plant extracts stored in the dark oxidised significantly (p < 0.05) slower than the control sample and the sample with BHT. After 24 weeks of storage, the lowest peroxide value was in the sample with the lovage stem extract. The extracts contain compounds that could absorb light (for example chlorophyll) and in the light/dark conditions accelerate oxidation in oil. Among the analysed extracts the lovage stem extract was the most effective oil oxidation inhibitor, but horseradish leaf extract was the most effective DPPH radical scavenger.
