Effects of Key Fatty Acids on the Development of Warmed-over Flavor in Surimi Gels and Their Molecular Transformation Pathways

High-temperature heating and sterilization of surimi products stored at ambient temperature often result in the development of warmed-over flavor. To understand the formation pathway of this off-flavor and facilitate its targeted elimination, this study investigated the effects of linoleic acid, oleic acid, and linolenic acid on the development of warmed-over flavor in silver carp surimi gels heated up to 100 ℃. A myofibrillar protein-fat model system was constructed to elucidate the conversion pathway of isotopically labeled linoleic acid during the thermal processing of surimi gels using the isotopic tracer technique. The results showed that the warmed-over flavor in surimi gels increased significantly with the addition of each of the three fatty acids, with linoleic acid exhibiting the most potent effect. In the gel supplemented with linoleic acid, the contents of 15 volatile compounds contributing to the warmed-over flavor increased significantly. In particular, the contents of unsaturated aldehydes such as (E,E)-2,4-decadienal, (E)-2-octenal, (E)-2-nonenal, (E)-2-decadienal, and (E,E)-2,4-heptadienal were 2.06, 3.72, 2.84, 1.84, and 2.07 times as high as those in the control group, respectively. Additionally, 10 odor compounds including isotopically labeled heptanal, octanal, nonanal, decanal, (E)-2-octenal, (E)-2-nonenal, (E)-2-decenal, (E,E)-2,4-decadienal, 1-octen-3-ol, and nonanoic acid were detected in the linoleic acid reaction system, whose peak areas increased during thermal processing. Octanal, heptanal, nonanal, decanal, (E)-2-nonenal, and (E,E)-2,4-decadienal were identified as key contributors to the warmed-over flavor.