Steaming before or after freezing preserves the nutritional and aroma quality of sweet corn

Sweet corn is often preserved by freezing; however, freezing and subsequent cooking may promote biochemical changes that affect its nutritional and sensory quality. In this study, an integrated metabolomics approach was used to characterize the effects of boiling and steaming before or after short-term freezing. Across six treatments, 1488 metabolites belonging to 26 chemical classes, including sugars, phenolic acids, flavonoids, lipids, amino acids, and aroma-related compounds, were identified and showed process-dependent changes. Boiling caused the greatest compositional changes, including reductions in glucose, fructose, sugar alcohol, and several phenolic and lipid derivatives, which may be associated with leaching and thermal degradation. In contrast, steaming before or after freezing retained higher levels of bioactive phenolic acids, luteolin-derived flavonoids, linoleic acid-related lipids, and key saccharides. Sorbitol and xylitol were reduced by freezing alone, whereas these losses were partly alleviated when steaming was applied before or after freezing. Volatile profiling showed that boiling and freezing reduced overall flavor complexity, while steaming maintained better, sweet, floral, and buttery aroma attributes. KEGG pathway analysis indicated that steaming was associated with better preservation of carbohydrate, phenylpropanoid, and flavonoid metabolism than boiling or freezing alone. Overall, these results suggest that steaming, either before or after short-term freezing, is a favorable processing strategy for maintaining the nutritional metabolite profile and aroma quality of sweet corn under the tested conditions.