Effects of pressing temperature on selenium speciation, volatile profiles, and sensory evaluation in...

Pressing temperature strongly influences the nutritional and flavor properties of selenium-enriched rapeseed oils (SROs). In this study, five SROs were obtained at 50-60 °C (CPO), 70-80 °C (LPO), 90-100 °C (MPO), 110-120 °C (SPO), and 140-150 °C (HPO) to evaluate changes in selenium (Se) speciation, volatile profiles, and sensory attributes. The total Se content decreased significantly with increasing temperature, from 428.10 ± 21.69 μg/kg in CPO to 147.64 ± 3.12 μg/kg in HPO. Organic Se species, primarily selenomethionine, selenocystine, and Se-methylselenocysteine, were the dominant forms and exhibited higher thermal sensitivity, with reductions of 85.19 %, 66.20 %, and 74.96 % from CPO to MPO, respectively. Subsequently, their levels remained low with a less pronounced decline at higher temperatures. The diversity and abundance of volatile organic compounds (VOCs) increased with pressing temperature, with total VOC content rising by 2.84-fold, from 212.10 μg/kg in CPO to 602.35 μg/kg in HPO. Nitriles, sulfur-containing compounds, and heterocyclics increased markedly at higher temperatures, whereas aldehydes, alcohols, ketones, and phenols predominated in low-temperature SROs. PCA explained 84 % of the variance and clearly distinguished between cold- and hot-pressed samples, confirming the significant impact of pressing temperature on VOC profiles. Sensory evaluation revealed that low-temperature SROs were characterized by a predominant green aroma, associated with aldehydes, alcohols, and ketones, while high-temperature SROs displayed stronger roasted/nutty, burnt, pungent, and smoky notes, attributed to elevated levels of nitriles, sulfur compounds, and heterocyclics. These findings provide valuable insights for optimizing Se retention and flavor quality during SRO processing.