Effect of water changes on aroma compounds in cooked Penaeus vannamei during frozen storage

Cooked Penaeus vannamei shrimp are popular among consumers for their characteristic fresh flavor and ready-to-eat convenience. To investigate how moisture dynamics during frozen storage impact the aroma quality of cooked P. vannamei, we tracked changes in moisture content, protein and lipid oxidation, microstructural integrity, and volatile aroma compounds over time. Our findings show that the water-holding capacity of the shrimp decreases significantly during frozen storage. This is evidenced by a marked increase in thawing, cooking, and centrifugal losses (P<0.05), alongside a clear drop in overall water content. Simultaneously, we observed a synchronized trend of protein and lipid oxidation: total sulfhydryl content and Ca²⁺-ATPase activity dropped significantly as storage time increased (P<0.05), while carbonyl and malondialdehyde (MDA) levels rose. Microscopic observations confirmed that the myofibrillar structure of the shrimp became increasingly loose, leading to large cavities, structural collapse, and a complete loss of tissue integrity. Furthermore, electronic nose (E-nose) analysis detected a continuous accumulation of volatile compounds—primarily hydrocarbons, sulfides, and amines—throughout the storage period. Using gas chromatography-olfactometry-mass spectrometry (GC-O-MS), we identified 67 volatile aroma compounds and isolated 12 key aroma drivers based on their odor activity values (OAV > 1) and flavor dilution factors (FD > 8). Pearson correlation analysis highlighted a strong structural relationship between physical quality and aroma. Water loss metrics showed a strong positive correlation with oxidation markers (carbonyl and MDA) and a strong negative correlation with protein health markers (sulfhydryl and Ca²⁺-ATPase) and total water content. Importantly, moisture indicators were significantly linked to four critical aroma compounds: isoamyl acetate, ethyl 4-methylvalerate, 2-pentylfuran, and 2-acetyl-1-pyrroline. Ultimately, the data suggests that moisture loss during frozen storage accelerates protein and lipid oxidation, a process that directly drives the degradation of certain key aromas (such as isoamyl acetate and 2-pentylfuran) and the formation of others (such as 2-acetyl-1-pyrroline).