Controlled accelerated oxidation of oleic acid using a DBD plasma: Determination of volatile oxidation compounds

Abstract

Lipid oxidation is one of the main causes of food deterioration, resulting in the loss of nutritional properties and the formation of unwanted aroma properties. Both for scientific and industrial purposes there is a need for accelerated lipid oxidation tests in food research. The conventional thermally-based accelerated lipid oxidation protocols are known to insufficiently correlate to the realistic oxidation mechanisms. Recent studies have investigated the application of an innovative non-thermal plasma technique as a promising alternative approach. The produced reactive oxygen species in non-thermal plasma enabled to accelerate the lipid oxidation process, with a more accurate prediction of antioxidative properties, thus leading to a higher correlation with the product oxidized at room temperature. In order to obtain more profound insights in the plasma-induced chemistry, a profound parameter study was performed by studying the impact of applied voltage, plasma gas composition, distance between nozzle and sample surface, ambient gas composition and treatment time. Using analytical tools (HS–SPME–GC–MS) on one hand, combined with statistical interpretations (PCA/SIMCA/HCA) on the other hand, a selection of the most promising parameter settings was done. For this parameter study, pure oleic acid was used as a model matrix. In the sample oxidized at 25°C, typical oxidation products have been found, such as heptanal, octanal, nonanal, (E)-nonenal, etc.…Comparing the different plasma types (argon, argon/O2 and argon/H2O) in different surrounding gas compositions (air, argon) showed most promising results for Ar/O2 in Ar atmosphere. A correlation of up to 82% was found between the sample oxidized at 25°C and the plasma treated sample.