The kinetics of the inactivation of Escherichia coli in organic broccoli sprouts by mild heat (MH) and lactic acid (LA) were investigated. In vitro survival kinetics showed that the cell number decreased dramatically and was not detectable after 120–135 s under combination treatment. Protein leakage and atomic force microscopy analyses showed that inactivation of E. coli cells resulted from disruption of the outer membrane by the sanitisers. LA almost destroyed the outer membrane and induced high protein leakage (3.78–10.75 μg/mL). MH enhanced the membrane damage caused by LA. The in vivo inactivation and following recovery during storage suggested that the combination treatment presented a potential inactivation process for organic vegetables or sprouts. Weibull model with higher R2 values (0.66–0.99) best described the in vitro antibacterial kinetics and in vivo recovery dynamics. Moreover, the metabolic analysis revealed that citrate cycle (TCA) and amino acid metabolism contributed to the adaptive responses.

Seafood is a good source of essential nutrients, but the presence of pyrethroid contaminants may pose risks to consumers’ health and its intricate matrices obstruct chemical hazard detection. In this study, a method for detecting residues of four pyrethroids (cypermethrin, deltamethrin, permethrin, and bifenthrin) in fish and finfish was optimized and validated. The proposed method performed with low-temperature cleanup (− 20 ◦C) followed by nanoparticle-extraction and HPLC-PDA. The critical parameters of the method’s performance were studied to demonstrate the optimum conditions. The method was verified using mackerel fillet, and its application was extended to determine pyrethroid residues in commonly consumed seafood (salmon, sea bass, threadfin fish, tiger prawn, vannamei prawn, shrimp, squid, grand jackknife clam, and oyster) obtained from local supermarkets in Singapore. The proposed method provided satisfactory recoveries of 75.95–96.81% and achieved LOQs of 0.54–0.85 ng/g, presenting the accomplishment for pyrethroid determination in seafood. Among tested seafood samples, at least one of the target pyrethroids was monitored (0.28–11.28 ng/g); however, the residue was below the level with safety concern. Estimated hazard indexes (≤0.12%) from risk assessment indicate a negligible risk of exposure to four target pyrethroids via consumption of seafood in Singapore.

This study aimed to better understand the overall metabolic responses of Escherichia coli biofilms to the combined stresses of ultrasound and low concentration acidic electrolysed water (LcAEW, free available chlorine: 4 mg/L). The inactivation kinetics of all E. coli strains (ATCC 25922, ATCC 35150 and ATCC 43895) were simulated well by the modified Weibull model (R2: 0.81–0.97; RMSE: 0.04–0.71). By analysing metabolite profiles, ultrasound mainly disrupted nucleotide metabolism in E. coli cells within biofilms, as most intracellular nucleotide-related compounds (e.g., uridine, ATP, ADP) showed decreased trend especially in ATCC 25922 and ATCC 35150. Increased contents of most amino acids and decreased contents of most carbohydrates were shown in all strains after LcAEW treatment. Under combined treatment, adaptive strategies like glutamate decarboxylase system and mixed acid fermentation were activated to different extents among the three strains. These findings revealed that NMR-based metabolomics technology is promising in identifying strain-specific metabolic responses of biofilms to different antimicrobial treatments, providing guidance for future mechanism studies related to food contact surface sanitisation.

Mammalian gelatin is extensively utilized in the food industry because of its physicochemical properties. However, its usage is restricted and essentially prohibited for religious people. Fish gelatin is a promising alternative with no religious and social restrictions. The desirable properties of fish gelatin can be significantly improved by various methods, such as the addition of active compounds, enzymes, and natural crosslinking agents (e.g., plant phenolics and genipin), and nonthermal physical treatments (e.g., ionizing radiation and high pressure). The aim of this study was to explore whether the properties of fish gelatin (gel strength, melting or gelling temperature, odor, viscosity, sensory properties, filmforming ability, etc.) could be improved to make it comparable to mammalian gelatin. The structure and properties of gelatins obtained from mammalian and fish sources are summarized. Moreover, the modification methods used to ameliorate the properties of fish gelatin, including rheological (gelling temperature from 13–19◦C to 23–25◦C), physicochemical (gel strengths from ∼200 to 250 g), and thermal properties (melting points from ∼25 to 30◦C), are comprehensively discussed. The relevant literature reviewed and the technological advancements in the industry can propel the development of fish gelatin as a potential alternative to mammalian gelatin, thereby expanding its competitive market share with increasing utility.

Ice is widely used for the preservation of perishable seafood but not much effective in killing bacteria. Herein, in this study, we aimed to investigate the effect of slightly acid electrolysed water (SAEW) ice on the microbial spoilage together with the quality parameters to elucidate the underlying preservative mechanism. The results indicated that SAEW ice exhibited inhibitory activity toward polyphenol oxidase (PPO) and acid phosphatase (ACP) with 55.3% and 61.9% reduction of activity at day 7, respectively, along with less discolouration and the lowest K-value of shrimp. Besides, the growth of aerobic mesophilic and psychrotrophic bacteria was retarded by SAEW ice treatment (2.4 and 0.4 log CFU/g reduction, respectively). 16S rDNA-based Illumina sequencing elucidated that SAEW ice efficiently retarded the growth of Proteobacteria. Specifically, the growth of major spoilage genus presented in tap water (TW) ice treated shrimp (Shewanella, Vibrio, and Aeromonas) and NaCl ice treated shrimp (Psychrobacter) was inhibited in SAEW ice treated shrimp, which further led to the smallest increase of putrescine and cadaverine, together with the lowest values of pH and TVB-N during storage. The sensory results indicated that SAEW treatment maintained the quality of shrimp during storage in terms of colour, appearance, and texture. Overall, the SAEW ice exhibited a promising preservative effect on shrimp.

Escherichia coli outbreaks linked to wheat flour consumption have kept emerging in recent years, which necessitated an antimicrobial step being incorporated into the flour production process. The objectives of this in vivo study were to holistically evaluate the sanitizing efficacy of thermal treatment at 60 and 70°C against the “big six” E. coli strains (O26:H11, O45:H2, O103:H11, O111, O121:H19, and O145) in wheat flour and to assess the strain-specific metabolic responses using nuclear magnetic resonance (NMR) spectroscopy. The 70°C treatment temperature indiscriminatingly inactivated all strains by over 4.3-log CFU/g within 20 min, suggesting the high sanitization effectiveness of this treatment temperature, whereas the treatment at 60°C inactivated the strains to various degrees during the 1-h process. The most resistant strains at 60°C, O26 and O45, were characterized by amino acid and sugar depletion, and their high resistance was attributed to the dual effects of activated heat shock protein (HSP) synthesis and promoted glycolysis. O121 also demonstrated these metabolic changes, yet its thermal resistance was largely impaired by the weakened membrane structure and diminished osmotic protection due to phosphorylcholine exhaustion. In contrast, O111, O145, and O103 presented a substantial elevation of metabolites after stress at 60°C; their moderate thermal resistance was mainly explained by the accumulation of amino acids as osmolytes. Overall, the study enhanced our understanding of the metabolic responses of big six E. coli to heat stress and provided a model for conducting NMR-based metabolomic studies in powdered food matrices.

Pyrethroid contamination in fish can contribute to the dietary uptake of pesticides. To mitigate this risk, the effects of frozen storage, thermal treatments (boiling and grilling), and non-thermal treatments (pickling and curing) on the reduction of bifenthrin, cypermethrin, deltamethrin, and permethrin in mackerel fillets were investigated. The curing process was the most effective method that significantly depleted 74.82–79.45% of pyrethroid residues from fish fillets, followed by the synergistic effect of eight weeks’ frozen storage and grilling method (69.19–78.31%). Moreover, pyrethroid degradation pathways in processed fish were proposed into three major mechanisms of C1-C3 bond cleavage in cyclopropyl, dehalogenation, and double bond cleavage. These identical pathways incorporated with additional four mechanisms of dimerization, ester hydrolysis, oxidation, and reduction. This study recommended simple and effective processing practices for consumers and/or manufacturers to enhance food safety from the potential risks of consuming pyrethroid-contaminated fish.

Global fisheries pressure generates interest in sustainable seafood production and developing plant-based seafood. This study took fishball as an example of seafood products applying konjac glucomannan (KGM) in developing plant-based fishball (PFB) analogues mimicking the texture of fishball. Increasing KGM concentration (up to 8.0%) influenced texture and rheological properties of PFB progressively, where the hardness, chewiness, and gel strength of PFB were significantly enhanced. Decreased pH value (9.38 to 7.93) and increased α-helix, β-sheet, and helix/coil ratio (1.40 to 1.70%) validated a promotion of hydrogen bonds and ordered structures by KGM. The strengthened interaction strength and hydrogen bonds formed at -OH groups of KGM and amide linkage of soy protein could be responsible for textural improvement. A more compact and regular microstructure also validated a firmer texture in PFB with higher KGM levels. Besides, KGM (3.5–8.0%) significantly decreased instantaneous compliance J0 (101.3 × 10−6 to 58.1 × 10−6 Pa−1), indicating denser crosslinks and firmer structures. In conclusion, KGM improved the texture and viscoelasticity of PFB and had an excellent application value in developing plant-based seafood analogues.

The potential of organic acids to inactivate foodborne pathogens in food industry has gained attention, while the sanitizing mechanism of acid stress has not been explained fully at metabolomics level. The aim of this study was to elucidate the antimicrobial mechanism of low-concentration organic acids (1.5% acetic acid, 1% citric acid, and 1.5% lactic acid) on Salmonella enterica strains (ATCC 6962, ATCC 13076, and ATCC 14028) inoculated on cucumber slices. Flow cytometry, nuclear magnetic resonance (NMR) combined with multivariate data analysis revealed that the population of S. enterica reduced 1.7–2.5 log CFU/g after different organic acid treatments. Bacterial membranes (2.37–19.00%) were destroyed and nucleic acid exposed, 40.27–85.33% of membranes was partially damaged, and 44 metabolites were identified from these three strains. The amino acids (Trp, Met, and Val) decreased significantly. Conversely, the intracellular organic acids and hydrocarbon grew obviously. The flux of marked metabolites showed that metabolisms of energy, amino acids, and carbohydrates pathways were disturbed which included TCA cycle, glycolysis, and biosynthesis of amino acids. The antibacterial mechanism on S. enterica provides clue to enhance the application of organic acids in controlling foodborne pathogens on fresh produce.

Essential oils (EOs), such as thyme (Thy) and cinnamon (Cin) oils, present promising antibacterial properties against foodborne pathogens (e.g., Salmonella enterica serovar Typhimurium). However, the food matrix might result in sublethal EO stress, and little information about direct and/or cross-resistance development after sublethal EO exposure is available. This study revealed that S. Typhimurium under sublethal Thy and Cin (50% minimum inhibitory concentration, MIC50) treatments exhibited a lower growth rate and an extended lag phase. EO adapted cells showed direct-resistance to subsequent lethal EO treatment, and cross-resistance to thermal (58 °C) and oxidative (hydrogen peroxide, 50 mmol/L) stresses. Metabolomics analysis revealed changes of 47 significant metabolites (variable importance in projection > 1, false discovery rate (FDR) < 0.05), including lipids, oligopeptides, amino acids, nucleotide related compounds, and organic acids. Metabolic pathways, such as aminoacyl-tRNA biosynthesis, were shown to be involved in EO adaptation. Furthermore, a transcriptomics study identified 161 differentially expressed genes (DEGs, fold change > 2, FDR < 0.05) in MIC50 Thy treated cells, while more DEGs (3 2 4) were screened from the MIC50 Cin group. The integrated omics analysis allowed us to speculate on the molecular mechanisms. Under harsher Thy stress, S. Typhimurium cells adopted a conservative strategy to survive. By contrast, more radical responses were observed during Cin adaptation. In conclusion, the food industry should be more cautious in the use of EOs because sublethal EO stress might result in the development of resistance.