Decoding flavor evolution during refining of DHA-rich Schizochytrium oil: a multidimensional framework integrating sensory evaluation and volatile metabolomics

The influence of refining conditions on flavor evolution of Schizochytrium oil remained unclear. Crude oil exhibited strong fishy and sour odors, with 3-octen-2-one and 5-ethyl-2(5H)-furanone as key off-flavor contributors. Degumming and deacidification marginally improved these odors, while decolorization paradoxically intensified fishiness by selective removal of masking compounds. Deodorization was critical: 170 °C had limited effects; optimal performance at 190 °C/30 min largely eliminated off-flavors and allowed a mild pleasant aroma to emerge. Under this condition, eight volatile metabolites were significantly reduced, serving as a practical biomarker panel. Notably, non-key odorants with rOAV < 1 also contributed to flavor via matrix effects. In contrast, 210 °C induced thermal degradation, causing a rebound of aldehydes and ketones that compromised flavor quality. This reveals a biphasic mechanism: volatile removal below 190 °C versus off-flavor rebound above 210 °C, offering both mechanistic insight and practical utility for oil refining.