Non-volatile taste active compounds and umami evaluation in two aquacultured pufferfish (Takifugu obscurus and Takifugu rubripes)

Effects of slightly acidic electrolyzed water pretreatment combined with biopreservatives on the shelf life of refrigerated obscure pufferfish (Takifugu obscurus)

This study assessed the effects of ε-polylysine hydrochloride (ε-PLH) and rosemary extract (RE) combined with slightly acidic electrolyzed water (SAEW) on the shelf life of obscure pufferfish (Takifugu obscurus) during refrigerated storage at (4 ± 1 °C). The samples were first dipped in SAEW and then treated with sterilized water (CK) and other solutions (0.2% RE [RE], 0.3% ε-PLH [PLH], and 0.2% RE + 0.3% ε-PLH [RE+PLH], respectively). Afterwards, microbiological, physicochemical, water migration, and sensory attributes were periodically assessed. The results showed that compared with CK and RE groups, ε-PLH treatment could effectively inhibit microbial growth and delay the increase in total volatile base nitrogen (TVB-N). In addition, microbial indexes, TVB-N, thiobarbituric acid, and metmyoglobin value in the samples treated with RE+ε-PLH were lower than those with ε-PLH or RE alone during storage. Meanwhile, samples treated with RE+ε-PLH exhibited the best sensory properties and no effect on color parameters. Based on the results of microbiological analysis, the shelf life of obscure pufferfish treated with RE+ε-PLH was 14 days during refrigerated storage at (4 ± 1 °C). PRACTICAL APPLICATION: In our study, the combined application of ε-PLH, RE, and SAEW was effective to extend the shelf life of obscure pufferfish. Based on the results of total viable counts, the RE+PLH group had a shelf life of approximately 14 days. Accordingly, bio-preservatives combined with SAEW technology have a broad application potential in the storage of obscure pufferfish.

Nonvolatile taste compounds of Shanghai smoked fish: A novel three stages control techniques

In this work, the effect of processing stages including first soaking (FS), frying after first soaking (FFS), and second soaking (SS) on nonvolatile taste compounds of Shanghai smoked fish was investigated using high-performance liquid chromatography (HPLC) and automatic amino acid analyzer. Results showed that the contents of free amino acids (FAAs) ranged from 396.94 to 585.79 mg/100 g and 5'-inosine monophosphate (IMP, as main umami nucleotide) from 215.91 to 284.56 mg/100 g in Shanghai smoked fish, respectively. Moreover, the contents of Glu and Gly as main umami amino acids ranged from 1.64 to 107.32 mg/100 g and 61.61 to 108.88 mg/100 g, respectively. TAV values of IMP, Asp, and Glu in Shanghai smoked fish reached 11.38, 2.73, and 21.46, respectively. The obvious difference could be observed using principal component analysis (PCA) in three processing stages of Shanghai smoked fish. Therefore, probing into the nonvolatile flavor of Shanghai smoked fish could not only enrich the theoretical basis of flavor chemistry in freshwater fish fields, but probe into the formation mechanisms of taste compounds in further study.

Effects of microwave time on quality of grass carp fillets processed through microwave combined with hot-air drying

In this study, the quality changes of grass carp fillets dried by microwave-hot-air combined drying under different microwave time were investigated. The salted fillets were dried at 385 W microwave with different time (0, 2, 4, 6, 8, and 10 min), followed by 65℃ hot air to the end. The quality of fillets was evaluated by drying time, color, hardness, rehydration ratio, and taste characteristics (ATP-related compounds, free amino acids, E-tongue taste profile, EUC, and TAV). Results showed that grass carp fillets dried by microwave-hot-air combined drying had better qualities compared with single hot-air drying. Besides, microwave time had obvious effects on the quality changes of grass carp fillets, and 6 min was considered as the optimal drying time.