Effect of raw material frozen storage on physicochemical properties and flavor compounds of fermented mandarin fish (Siniperca chuatsi).

Frozen mandarin fish (MF) is utilized for preparation fermented MF. However, how raw material (RM) affects the quality and flavor of fermented MF is unclear. This study investigated the impact and mechanism of RM frozen storage on the microstructure, texture, water distribution, and flavor of fermented MF by light microscopy, texture profile analysis, low-field nuclear magnetic resonance, gas chromatography-ion mobility spectrometry, and multivariate analysis. With increasing RM frozen storage time, both frozen MF and frozen-based fermented MF decreased in muscle fiber density while increased in muscle fiber diameter. Additionally, RM frozen storage exhibited a significant impact on the water distribution of frozen MF, while no obvious effect on that of frozen-based fermented MF. Seven odorant (2-methyl-1-propanol, 3-hydroxy-2-butanone, 2,3-butanedione, hexanal-D, ethyl acetate-D, 3-pentanone, and acetone) were shown as potential markers to distinguish fermented MF. This study could provide a theoretical basis for the production of high-quality frozen-based fermented MF.

Molecular mechanism of high-pressure processing for improving the quality of low-salt Eucheuma spinosum chicken breast batters.

To confirm the role of high-pressure processing in enhancing the quality of Eucheuma spinosum chicken breast batters, low-field nuclear magnetic resonance, scanning electron microscopy and Raman spectroscopy were used to explore the effect of E. spinosum and high-pressure processing on water migration, protein conformation, and microstructure in chicken breast batters. The water-holding capacity, surface hydrophobicity, and reactive sulfhydryl group content significantly increased as the pressure increased (0.1 to 300 MPa), while the peak ratio of non-flowable water (T22) decreased (P > 0.05). The secondary structure composition changed significantly, and the ß-sheet, ß-turn, and random coil content significantly increased (P < 0.05) as the α-helix content decreased. The -OH stretching vibration (3,100 to 3,500 cm-1) was shifted to higher wavenumbers, and the number of hydrogen bonds in each water molecule increased. The scanning electron microscopy images reveal that proper pressure produced a dense network structure with small cavities. Moreover, these characteristics were further enhanced when E. spinosum was added from 0 to 0.4%. Overall, this paper could provide crucial theoretical support for the application of high-pressure processing of low-salt seaweed chicken breast.