农林科学最新文献

This study aimed to evaluate the behavior of Pseudomonas aeruginosa (PSA) in natural mineral water sourced from three different extraction wells and stored at various temperatures (10, 12, 20, 23, and 30 °C) to calculate the kinetic growth parameters of this microorganism through predictive modeling. The physicochemical characterization of waters was also evaluated at the time of collection, and included the analysis of 40 different minerals, and quality parameters such as pH, conductivity, oxidation-reduction potential (ORP), total dissolved solids (TDS), salinity (PSU), and temperature (T). PSA survived in raw mineral water incubated at 12, 20, 23, and 30 °C; however, no growth was observed at 10 °C. Growth curves started with an initial population of ∼ 2.5-3 log CFU/mL, and final PSA populations ranged from 3.5 to 4.9 log CFU/mL. The maximum specific growth rate (μ_max) at 30 °C varied among the wells, with Well P-07 showing the highest growth rate (0.2 h^-1), followed by Well P-08 (0.195 h^-1) and well P-01 (0.133 h^-1). At 12 °C, well P-01 exhibited the highest growth rate (μ_max = 0.22 h^-1), indicating a influence of mineral composition in the growth of PSA. The lag time (λ) also varied, with minimum values of 2.4 ± 0.1 h at 30 °C and maximum values of 41.6 ± 0.2 h at 12 °C. From these primary estimated parameters, it was possible to obtain five robust secondary models to describe the influence of temperature on the maximum growth rates and lag phase of PSA in the well. The estimated PSA growth parameters at 20 and 23 °C were subjected to a hierarchical cluster analysis and correlation plots to verify the influence of the physicochemical composition of the waters on the PSA behavior at each well's specific annual average temperature. This analysis confirmed a positive relationship (p < 0.05) between the presence of minerals (Ca, Fe, Sr, Mn, Na) and ions (SO₄^-3, Cl^-) and the PSA lag phase time. These results underscore the need for tailored water quality management strategies that consider chemical composition and temperature to address specific microbial contamination risks.

Salmonella is one of the most common bacterial foodborne pathogens and is frequently found as a contaminant of raw egg-based foods. Food safety regulations recommend the use of food acids to mitigate the risk of Salmonella persistence in raw egg-based foods. Salmonella, however, can become tolerant to acidic environments and it is not known how this can affect bacterial persistence in food. This study investigated whether acid-tolerant strains of Salmonella persisted longer in mayonnaise compared with sensitive strains. Isolates of S. typhimurium, S. infantis, S. enteritidis, and S.hessarek were used in this project. Acid-tolerant Salmonella strains were generated using a three-day step-down method where pH was decreased every 24 h from pH 7 to pH 5. Growth curves were determined for both acid-sensitive and acid-tolerant strains. Time-kill experiments were conducted to compare the survivability of acid-sensitive and acid-tolerant Salmonella serotypes in mayonnaise stored at either 5 °C or 25 °C for 72 h. Salmonella exhibited an extended lag phase with increased acid concentration, and acid-tolerant strains recovered faster in media compared with acid-sensitive strains. Elevated biofilm formation was found in acid-habituated strains compared to sensitive strains, and this varied between serotypes. The culturability of Salmonella in mayonnaise stored at 5 °C declined slower than when stored at 25 °C. Acid-tolerant strains persisted longer in mayonnaise and there was a statistically significant difference in culturability (P < 0.05). In conclusion, the current safe food recommendations to control Salmonella in raw egg-based foods are not effective in eliminating it.

Staphylococcus aureus is a major cause of gastroenteritis, commonly associated with the consumption of food contaminated at any stage of the food supply chain. Sous vide seafood has the potential to be a vehicle for the spread of S. aureus and enterotoxins due to low temperature cooking. This study aimed to investigate the antimicrobial activity of quince leaf extracts and the impact on the survival of S. aureus during sous vide process at frequently utilized temperatures. The results of the disk diffusion assay demonstrated the antibacterial efficiencies of extracts obtained using ethanol and methanol, with inhibition zone diameters of 9.8 and 11.2 mm, respectively. In contrast, aqueous extract had no effect on the bacteria. Since methanolic extract was the most effective one, phenolic profile was analyzed. Quercetin-3-O-rutinoside was the major compound (43.0 %) followed by 3-O-caffeoylquinic acid (21.8 %). Quince leaf methanolic extract (QM) was added to seabream to examine the thermal inactivation kinetics of S. aureus. The D values of QM-treated group ranged from 9.80 and 0.39 min, while those of the untreated samples varied between 11.36 and 0.51 min at 56-62 °C. The addition of QM to sous vide seabream significantly reduced the time needed to inactivate S. aureus. The z values of S. aureus in QM and untreated groups were 4.19 and 4.32 °C, respectively. Beneficial results could be achieved by adding quince extracts thereby; reducing S. aureus in sous vide fish and enhancing food safety. Developing efficient thermal processing techniques and combining additional hurdles are promising strategies for accomplishing pathogen inhibition.

Photodynamic inactivation, as a safe and effective antimicrobial technology that does not damage the organoleptic properties of the food itself, decreases the use of preservatives and is gradually gaining attention in the food industry. This study selected octyl gallate (OG) as an antimicrobial photosensitizer with eucalyptus oil as the oil phase and prepared it as an octyl gallate nanoemulsion (OG-NE) to ensure the delivery of the photosensitizer. Escherichia coli and Staphylococcus aureus inactivation with the OG-NE combined with photodynamic technology, as well as the effect on the quality of food products, was investigated. The results showed the successful preparation and homogeneous distribution of the OG-NE with an encapsulation rate of 85.18 %. The OG-NE's ability to produce single oxygen (¹O₂) was significantly higher, as shown by ¹O₂ production. The OG-NE combined photodynamic technique confirmed the effectiveness of microbial removal, demonstrating a significant increase in reactive oxygen species (ROS) and the permeability of the cell membrane. The effect of the OG-NE combined photodynamic technology on perch (microbiology, pH, whiteness, water holding capacity, TVB-N and TBA) and litchi (weight loss, titratable acid and sugar content) preservation was assessed. Food preservation experiments revealed that the OG-NE combined photodynamic technology exhibited a positive effect on food quality. The results indicated that the combination of the OG-NE and photodynamic technology provided a new alternative strategy for the food industry in antimicrobial and preservation.

This work examined the attachment of porcine rotavirus (PRV) and Tulane virus (TV), a surrogate for human norovirus, to fresh and artificial phylloplanes of Romaine lettuce and Carmel spinach. The effect of produce type, sanitizer, and ultrasound treatment on removal of PRV and TV from produce and artificial surfaces was also investigated. Sanitization was performed with two oxidant-based sanitizers (chlorine and peroxyacetic acid) and one surfactant-based sanitizer (0.5 % malic acid +0.05 % thiamine lauryl sulfate) in combination with ultrasound. PRV and TV were spot inoculated to fresh and artificial produce surfaces and treated for 1 min with a sanitizing solution with and without ultrasound. No significant differences were observed in the attachment of PRV and TV to fresh and artificial leaf surfaces. The removal of PRV from produce leaves treated by different sanitizers was significantly higher than that of TV. No difference in viral removal between the fresh and artificial produce surfaces was found. The addition of ultrasound significantly increased viral removal from both type of produce surfaces. The removal of virus attached to fresh and artificial phylloplanes was virus-type, sanitizer-type, and produce cultivar dependent. Artificial phylloplanes may provide a novel platform for screening of sanitizers in food safety applications.

This study aimed to comprehensively examine the prevalence of L. monocytogenes and Listeria spp. in dairy products including raw milk, pasteurized milk, and cottage cheese, and identify potential risk factors for contamination throughout the dairy value chain in major milk sheds in Ethiopia. We collected 912 samples, comprising 736 milk samples (368 raw and 368 pasteurized) and 176 cottage cheese samples, from the Oromia, SNNP, and Amhara regions. The isolation of L. monocytogenes and Listeria spp. followed the EN ISO 11290-1: 2017 standards, with confirmation via PCR targeting the lmo2234 and iap genes. The overall prevalence rates were 12.2 % for Listeria spp. and 4.7 % for L. monocytogenes. Notably, the prevalence of Listeria spp. (P = 0.024) and L. monocytogenes (P < 0.001) varied significantly across regions. Raw milk showed the highest prevalence of Listeria spp. at 15.2 %, followed by pasteurized milk at 12.2 %, and cottage cheese at 5.7 %, with these differences being statistically significant (P = 0.006). The prevalence of Listeria spp. differed significantly (P = 0.001) among the value chain stages (producers, collectors, processors, and retailers) and was 12.5 %, 17.9 %, 17.4 %, and 7.1 %, respectively. Furthermore, the prevalence rates in cottage cheese from producers and retailers were significantly different at 6.8 % and 4.5 % (P = 0.001). The prevalence of L. monocytogenes among milk producers, collectors, and processors was also significantly different, at 4.4 %, 5.4 %, and 12.0 % respectively (P < 0.001). Filtration of milk and cooling for preservation of milk were significantly associated with Listeria spp. or L. monocytogenes contamination at milk collectors' level (P < 0.05). These findings underscore the need for targeted interventions focused on the risk factors identified here to mitigate Listeria contamination in the dairy sector.

The management of post-fermentation phase is essential for the protection of wine oxidation. The prolonged contact of yeast lees and wine can help to limit this problem, although off-flavours can originate. It is known that some cellular components (mannoproteins, lipids, glutathione, etc.) released into the wine influence oxygen protection; however, still active cells could contribute to maintaining protection against oxidation. To date, in the literature there is a lack of data that evaluates cell viability, especially in the post-fermentation phase, particularly using methods different by plate count that identifies only a small part of the viable population. The aim of the work was to investigate the yeast viability of 12 wine Saccharomyces cerevisiae strains during 45 days after the fermentation in natural grape juice. The major fermentation parameters were measured at early phase (40 h) and at the end of the process, and were correlated with total and viable cells in the post-fermentation phase. Contrary to what has been observed in the literature, this work demonstrates that cell viability in the post-fermentation phase is very high and dependent on the yeast strain. A predictive model that can estimate viability in the post-fermentation phase, based on parameters measured at the early fermentation phase, was successfully set up. This approach can be adopted by wineries or winemakers as it uses fermentation data (sugar and nitrogen residues, ethanol and glycerol production, total cell count) obtained through simple chemical and microbiological analyses.

Bacillus cytotoxicus is considered a potential emerging foodborne pathogen that has been under investigation in recent years. Most studies have focused on strains from vegetables, particularly potato products, but there is limited information on strains from other food sources. This study addresses the current research gap by investigating the genomic and phenotypic features of B. cytotoxicus isolated from edible insects. The whole genomes and key phenotypic traits of 20 strains isolated from edible insects were investigated. The comparative genome analysis also included 44 available genomes from other sources to identify possible genetic links and the mosaicism of virulence profiles (VP) and antimicrobial resistance genes (AMR). B. cytotoxicus isolated from edible insects showed marked thermotolerance, when vegetative forms could grow at 50-60 °C and survive at 65 °C and exhibited marked proteolytic activities, even at higher temperatures. The heterogeneous phenotypes observed suggest potential issues with defining suitable protocols for isolation and identification in this food matrix. Despite the limited genomic diversity observed, it was possible to identify links between isolates, demonstrating the co-isolation of different genomes/phenotypes from various insect samples and suggesting trade links between insect companies and the persistence of certain strains. A genomic comparison suggested segregating strains from edible insects with similar VP and AMR profiles. These findings indicate a degree of adaptation to different food niches, with strains from insects or insect-based products differing partially from those isolated from vegetable sources, showing possible associations with their respective food environments. The survival advantage conferred by thermotolerance underscores the need to assess the presence of these spore-forming bacteria carefully and to calibrate treatments and processes, to address the emerging risk posed by this pathogen and its implications for food safety.