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[Display omitted] • Comprehensive analysis of flavor formation of mandarin fish from smell and taste. • Nineteen key aroma compounds were identified in fermented mandarin fish. • The differential metabolites presented a significant correlation to the key volatiles. • 5′-nucleotides were reduced, whereas Asp and Glu were increased. • Tryptophan metabolism was the potential generation pathway of the fish stinky. Volatolomics and metabolomics were performed to explore the generation mechanism of the characteristic flavor of mandarin fish during fermentation. This study revealed a novel finding that umami-tasting amino acids, succinic acid, and peptides increased, while taste-presenting nucleotides decreased after fermentation. The results showed that 19 key aroma compounds were identified. The most nitrogenous compounds were produced after fermentation, the total concentration of which was >5 mg/kg. A high odor activity value of 443 was established for stinky indole. PLS-DA showed that sn -glycero-3-phosphocholine, hypoxanthine, creatine, and trimethylamine N -oxide were the key metabolites associated with the key volatiles. Umami-tasting amino acids could contribute to the characteristic taste. Metabolic pathway analysis revealed that tryptophan metabolism, trimethylamine metabolism, and monoterpenoid biosynthesis were the potential generation pathways of indole, trimethylamine, and terpenoids, respectively. Collectively, the results provide thoughts for targeted controlling the flavor of fermented mandarin fish. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-field measurement of nitrite as carcinogen is important for food safety. • A fully integrated colorimetric detection system for nitrite is offered. • APP is combined with DCNN as visual monitoring platform. • Validity period of test paper is prolonged from 7 d to more than 30 d. • The accuracy of food classification is high as 91.33–100% Nitrite is one of the most common carcinogens in daily food. Its simple, rapid, inexpensive, and in-field measurement is important for food safety, based on the requirements of the standard from Codex Alimentarius Commission and China. Using polyacrylonitrile (PAN) and thin layer silica gel (SG), p-aminophenylcyclic acid (SA) and naphthalene ethylenediamine hydrochloride (NEH), as carriers and chromogenic agents, respectively, PAN-NSS as nitrite color sensor is proposed. After fixing and protecting of SA and NEH with layer-upon-layer PAN, the validity period of the test paper can be prolonged from 7 days to more than 30 days. The reproducibility of PAN-NSS preparation is ensured by electrospinning. Combined with PAN-NSS, deep convolutional neural network (DCNN) and APP as a visual monitoring platform, which has the functions of rapid sampling, data processing and transmission, intuitive feedback, etc., and provides a fully integrated detection system for field detection. [ABSTRACT FROM AUTHOR]