Antioxidative advanced lipid oxidation end products in oils

Consumption of cold pressed oils rich in polyunsaturated fatty acids (PUFA) is considered healthy. However, these oils are characterized by a lack of oxidative stability, leading to the accumulation of lipid oxidation products, which have been shown to have detrimental effects on health. Thus, it is of utmost interest to find strategies to increase the oxidative stability of PUFA-rich oils. While many attempts have been performed to prolong the shelf life of edible oils by fortification with antioxidants and limiting factors, which promote lipid oxidation, no studies have been performed to evaluate the antioxidative effect of the enrichment of cold pressed oils with advanced lipid oxidation end products (ALEs). ALEs have been reported to have antioxidative activities and are formed by the non-enzymatic reaction between lipid aldehydes and aminophospholipids. We, therefore, aim at increasing the formation of ALEs in the PUFA-rich oil seeds, walnut, flax and safflower, and promoting the extraction of the ALEs from the seeds to the oil, thereby leading to cold pressed oils with prolonged shelf life. The development of edible oils with increasing oxidative stability will be achieved by firstly identifying novel antioxidantALEs formed after reaction betweenseed-specific phosphatidylethanolamines and lipid aldehydes by means of high-resolution mass spectrometry and two-dimensional nuclear magnetic resonance spectroscopy. Secondly, roasting conditions, which stimulate the generation of ALEs, and extraction procedures, which lead to enrichment of ALEs in oils, will be identified applying a holistic foodomics approach. Thirdly, the antioxidant mechanism of ALEs will be investigated using polarographic, photometric, mass spectrometric and electron spin resonance spectroscopic measurements. Finally, in a shelf life study, the oxidative and thermal stability of ALEs-rich oils will be compared with conventional oils low in ALEs. Methods to enrich cold pressed oils with ALEs will be evaluated to increase thermal stability and shelf life of PUFA-rich oils. So far, antioxidants are added after oil extraction to vegetable oils to raise their oxidative stability. The project will result in a new strategy to enrich edible oils with novel antioxidants by modifying production processes. 1

Rancidity in vegetable oils can occur with prolonged exposure to oxygen in the air, heat or light. This process, known as lipid oxidation, represents a challenge for the food industry and the consumers, as its progression leads to the formation to off-flavors and even some toxic compounds. Consuming vegetable oils that are rich in polyunsaturated fatty acids (PUFA) brings about many health benefits; however, these oils are especially susceptible to lipid oxidation, which compromises their quality and causes them to have a reduced shelf-life. Therefore, it is important to tackle this issue by investigating different strategies, such as cold-pressing to preserve the seeds' natural compounds when producing oils, or addition of natural antioxidants to the oils to delay the progress of lipid oxidation. Among lipid oxidation products, carbonyls are especially of concern, as they are strongly related to off-flavors and a reduced oil quality. Thus, this research investigated novel strategies to limit the presence of carbonyls in cold-pressed three vegetable oils: walnut, safflower seed and flaxseed oil, all of them with a high percentage of PUFA in their composition. Specifically, the enrichment with phosphatidylethanolamines (PEs), which are a class of natural antioxidants, was explored. The particular property about these antioxidants is their potential ability to track existing carbonyls in the oils and react with them, forming a series of compounds called advanced lipid oxidation end products (ALEs). By putting together a series of reaction models between PEs and different carbonyls, this research confirmed this potential ability. Afterwards, predictive analyses of oils enriched with PE reported a success in increasing the shelf-life of three oils of study. To further characterize the benefits of PE enrichment, a storage study simulating household conditions was performed, confirming the successful delay in lipid oxidation and preserving their quality of these oils, not only by achieving a reduced amount of carbonyls but other lipid oxidation products as well. On the other hand, additional efficiency for trapping specific carbonyls was observed when the oils were heated at 100 C. Therefore, this strategy could be a promising way to limit oxidation in cold-pressed oils but also in frying oils. In addition, this research evaluated the impact of seed crushing, roasting and PE enrichment prior to cold-pressing for oil production, providing key considerations to optimize oil yield while maintaining a low rancidity level. Overall, the research carried out by this project helped increase our understanding of oxidation prevention in PUFA-rich vegetable oils. The promising results found may potentially pave the way to develop strategies that can be used to obtain products with higher nutritional quality and shelf-life, and consequently reduce food waste.