Effect of cold and hot screw-pressing and mild physical refining on the quality and key aroma-active compounds in rapeseed oils

The research evaluates the quality and sensory attributes of cold and hot screw-pressed rapeseed oils, as well as mildly physically refined rapeseed oil obtained by short-path distillation. While commercial rapeseed oils are typically refined following solvent extraction, the presented study describes an alternative and more sustainable method used by a medium-sized processor, which employs hexane-free oil isolation followed by a specialized physical refining technique, with short-path distillation as a deodorization and deacidification stage. The results demonstrate that a mild physical refining process effectively removes undesirable compounds from crude oil, including pigments (up to 99% reduction) and glycerophospholipids (up to 95% reduction), while maintaining oxidative stability (induction period of 5.12 h) and minimizing the formation of trans -fatty acids (< 0.2%). Twenty-eight volatile compounds and twelve key aroma-active compounds (AACs) were detected among samples, with qualitative and quantitative differences depending on the processing method. Cold-pressed oils exhibited pronounced sensory notes driven by dominant AACs such as 4-isothiocyanatobutene, hexanal, and 1-hexanol (factor dilution – FD = 16), which contribute to musty, green, and pungent odor. Hot-pressed oils exhibited the same dominant AACs as cold-pressed samples, and additionally contained 6-methyl-5-hepten-2-one (FD = 16), γ-butyrolactone, 2-nonenal, 5-cyano-1-pentene (FD = 4), and 2-isothiocyanatobutene (FD = 2), contributing to an intensified pungent, musty, and cabbage-like aroma. Conversely, the mildly refined oils had a notable reduction in off-flavor volatiles, resulting in a clean sensory profile characterized by light green, cabbage-like, and nutty notes. These findings highlight the potential of mild physical refining as a sustainable and effective alternative to conventional solvent-based methods, offering high-quality rapeseed oil with favorable sensory and nutritional attributes.