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Vandamme J.,Research Group Molecular Odor Chemistry | Nikiforov A.,Ghent University | De Roose M.,Research Group Molecular Odor Chemistry | Leys C.,Ghent University | And 2 more authors.
Food Research International

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. © 2015 Elsevier Ltd. Source

Van Durme J.,Research Group Molecular Odor Chemistry | Nikiforov A.,Ghent University | Vandamme J.,Research Group Molecular Odor Chemistry | Leys C.,Ghent University | De Winne A.,Research Group Molecular Odor Chemistry
Food Research International

Non-thermal plasma technology has been investigated for the first time to induce realistic lipid oxidation reactions. Today accelerated lipid oxidation methods are often temperature-based although it is known that widely divergent kinetics and side-reactions occur as a function of the employed temperature. In this paper both a thermally-based reference test and experiments using three types of plasma (Ar plasma, oxygen-doped Ar plasma, water-doped Ar plasma) were investigated. Treatment of fresh reference vegetable oil with pure argon plasma did not induce lipid oxidation reactions. Contrarily, a short treatment with both 0.3% O2/Argon and 0.3% H2O/Argon plasmas resulted in the production of several oxidation products that were also identified in naturally oxidized oil. MS-fingerprinting analyses, supported by the degree of difference sensory testing, indicated that current plasma configuration induces changes that are different from these measured in naturally aged vegetable oil. Chemical profiling of the secondary volatile lipid oxidation products showed that atomic oxygen resulted mainly in aldehyde production, while singlet oxygen induced the formation of 2-pentyl furan. Vegetable oils exposed to Ar/0.3% H2O plasma were characterized by lower amounts of oxidation products. It can be concluded that plasma technology is an innovative and a promising technique to investigate the role of individual reactive species and/or unravel oxidation reaction pathways, with the potential to become a more representative accelerated food aging technique. © 2014 Elsevier Ltd. Source

Vandamme J.,Research Group Molecular Odor Chemistry | Nikiforov A.,Ghent University | Dujardin K.,Research Group Molecular Odor Chemistry | Leys C.,Ghent University | And 2 more authors.
Food Research International

Food products enriched with healthier unsaturated fatty acids are more sensitive to lipid oxidation, leading to an overall quality deterioration and the development of unwanted aroma properties. To evaluate the oxidative stability a wide range of techniques has been described in literature, of which most are thermally based. These unrealistic test conditions result in the induction of deviating oxidation chemistry compared to that observed during ambient storage. Non-thermal plasma technology is capable to generate a wide range of highly reactive oxidative species (e.g. atomic oxygen, hydroxyl radicals, singlet oxygen) while maintaining ambient temperatures. For the first time, a DBD-plasma jet (Ar/0.6% O2) is used on fish oil samples as a faster and more realistic accelerated lipid oxidation method. This paper critically evaluates both a thermal as a non-thermal plasma based accelerated oxidation protocol using naturally aged fish oil as reference. Experiments were done using both virgin, as alpha-tocopherol-enriched fish oil samples. Secondary lipid oxidation volatiles were measured using HS-SPME-GC-MS. Both accelerated oxidation techniques induced the formation of typical lipid oxidation markers (e.g. 2-propenal, (E)-2-pentenal, heptanal), however in both cases significant differences were observed compared to the naturally aged fish oil. On the other side, non-thermal plasma correctly predicted an antioxidative effect when 1000μg/g alpha-tocopherol was added to the fish oil, while thermally based tests resulted in the induction of prooxidative chemistry. Despite the differences with naturally aged fish oil, several non-thermal plasma characteristics (reactor configuration, gas feed mixture, power source, ...) can be fine-tuned to evolve towards a technology that is capable to accelerate lipid oxidation in a highly realistic manner. © 2015 Elsevier Ltd. Source

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