Non-Thermal Food Processing Technologies and Polyphenols: LC-MS Evidence for Stability, Transformation, and Functionality

Phenolic compounds contribute to the color, flavor, and functionality of foods but are often degraded during conventional heat treatments, prompting interest in non-thermal techniques. Thermal methods produce heat-driven changes that are more directly interpretable, whereas non-thermal methods require compound-resolved interpretation because higher post-treatment signals may reflect release from bound pools rather than true preservation. This review evaluates liquid chromatography-mass spectrometry (LC-MS) evidence on how ultrasound, high-pressure processing, pulsed electric fields, and cold plasma reshape polyphenol fingerprints across food matrices (2021-early 2026). Ultrasound and high-pressure processing preserve constitutive structures while increasing measurable phenolics through cell disruption and bound-pool release. Pulsed electric fields show similar release behavior but may shift toward oxidative losses when electroporation increases enzyme contact or downstream operations amplify degradation. Cold plasma introduces reactive oxygen and nitrogen species, with the clearest LC-MS/MS evidence for oxidation and nitration. In fresh-cut tissues, stress responses elevate phenylpropanoid products. Bulk assays such as total phenolic content (TPC) cannot separate preservation from release or true chemical conversion alone. LC-MS offers the compound-level detail needed to understand how each non-thermal technique changes polyphenol structure and functionality across food matrices.