International journal of food microbiology最新文献

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.

Contaminated food-contact surfaces are a potential route for spreading microorganisms to stone fruit during postharvest handling. The objective of this study was to investigate the factors that affect the transfer of bacteria from food-contact surfaces to stone fruits. Coupons (1 × 1 cm) of polyurethane (PU) or polyvinyl chloride (PVC) were inoculated with rifampin-resistant variants of Salmonella (five-strain cocktail) or Enterococcus faecium NRRL B-2354 at ~5 or ~7 log CFU/cm². Inoculated coupons (n = 8-11) were attached to a texture analyzer, and uniform contact conditions (5 N, 5 s) were used to explore the impact of bacterial species, inoculation level, donor surface, the presence of dried peach juice or wax, recipient produce commodity, and the dryness of inoculum. Whole fruits were transferred to 20 mL of 0.1 % peptone, rubbed for 2 min, and then the diluent was plated onto tryptic soy agar supplemented with rifampin at 50 μg/mL. Whole fruits were enriched when populations were anticipated to fall below the limit of detection (1.6 log CFU/fruit). At an inoculum of ~5 log CFU/coupon, Salmonella and E. faecium were recovered from the fruit by enrichment but not by plating. At ~7 log CFU/coupon, transfer rates, i.e., ratio of populations on recipient fruit to donor surface, were not significantly (P > 0.05) influenced by either bacterial species (Salmonella [0.26 % ± 0.77 %] versus E. faecium [0.068 % ± 0.071 %]) or donor surface (PU [0.085 % ± 0.098 %] versus PVC [0.16 % ± 0.16 %]). The rates of transfer of E. faecium from contaminated PU to peaches (0.050 % ± 0.031 %), nectarines (0.066 % ± 0.076 %), and onion skins (0.048 % ± 0.059 %) were not significantly different. The mean transfer rates of E. faecium increased significantly (P < 0.05) in the presence of dried wax (18 % ± 16 %) or peach juice (1.3 % ± 2.6 %) on the PU surface compared with the control (0.080 % ± 0.086 %). The transfer rates of E. faecium from contaminated surfaces were also significantly influenced by the drying time post-inoculation; the drier the inoculum, the lower the transfer rates. The presence of residues or moisture on food-contact surfaces facilitated the transfer of microorganisms during dry handling of fresh stone fruits. The results underscore the importance of implementing adequate cleaning, sanitation and, where appropriate, drying of equipment surfaces to effectively remove organic residues and mitigate the risks of cross-contamination.

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.

Daqu is a wheat-based fermentation starter essential for Chinese Baijiu production. The storage of daqu critically influences its quality. However, the assembly mechanisms of microbial communities in daqu during the storage phase and their impact on volatile flavor compounds remain unclear. This study investigated the microbial community assembly process and volatile compound profiles of daqu from three major regions of strong-flavor Baijiu production, Luzhou (LZ), Chengdu (CD), and Deyang (DY), during the storage phase. Fifteen biomarkers were identified across the regions using the random forest algorithm. Co-occurrence network analysis indicated that the LZ network was the most stable, while the CD network had the lowest complexity and stability, revealing 14 keystone species. Additionally, 42 differential volatile flavor compounds were identified. The analysis of microbial assembly mechanisms revealed that both stochastic and deterministic processes influenced the assembly of microbial communities in daqu during storage, as indicated by the modified stochasticity ratio (MST) and the neutral community model. Stochastic processes predominantly shaped the community of samples DY, while deterministic processes were more influential in the communities of samples LZ and CD. Notably, the important taxa (dominant microorganisms, keystone species, and biomarkers) were mainly influenced by deterministic processes, including temperature, dewpoint temperature, and surface air pressure, showing significant correlations with volatile flavor compounds. In conclusion, these findings highlight the effects of regional differences and storage processes on microbial community assembly and volatile flavor compounds in daqu, offering insights to regulate the daqu storage process and thereby optimize production.

Biofilms consisting of multiple species of bacteria compared to biofilms of single species are common in natural environments including food contact surfaces. The objective of this study was to understand the biofilm formation and the efficiency of sodium hypochlorite (50 ppm/5 mins) on the single and multiple species biofilm of Pseudomonas fluorescens, Staphylococcus aureus, and Listeria monocytogenes formed on stainless steel surfaces in static and continuous systems. The cell concentration of Listeria in the dual and triple species biofilm in the continuous system (7.3-8.4 log CFU/cm²) was higher compared to the static system (4.7-4.9 log CFU/cm²) while the concentration remained consistent in the single species biofilm (6.4-6.7 log CFU/cm²) for both systems. Biofilm formed in the static system was significantly (p < 0.001) more susceptible to sodium hypochlorite than biofilm formed in the continuous system. This observation agrees with the exopolysaccharide concentration which was found to be higher in the continuous system (8.0-15.6 μg/cm²) than in the static system (3.2-6.3 μg/cm²) indicating a positive correlation between EPS production and sanitizer resistance. Epifluorescence microscopy images showed the formation of interstitial voids within the three-species biofilm and filaments in the single and dual species Listeria biofilms in the continuous system which were absent in the static system. Overall, results showed that the biofilm formation and sanitizer resistance vary due to multispecies interaction and the presence of flow and should be considered an important variable in multispecies sanitizer resistance studies.

The Commission delegated Regulation (EU) 2024/1141 states that beef dry aging can be performed in a dedicated cabinet, at a surface temperature of -0.5 to 3 °C, maximum relative humidity of 85 %, air speed of 0.2-0.5 m/s and for a maximum of 35 days. Food business operators can apply different process parameters, even longer aging times, as long as they demonstrate to the competent authority that the aged meat is microbiologically safe. To support food business operators in the implementation of longer dry aging processes, in this study we investigated the behaviour of Listeria monocytogenes and Yersinia enterocolitica during beef dry aging in a patented cabinet up to 60 days. Beef loins were experimentally spiked with a mean load of 4.4 and 3.9 Log₁₀ CFU/g of Listeria monocytogenes and Yersinia enterocolitica respectively and stored at 1 °C, relative humidity 78 % and ventilation 2.0 m/s for 60 days. L. monocytogenes counts did not significantly change during the dry aging process, while Y. enterocolitica significantly increased up to 3 Log₁₀ CFU/g during the aging process and then tended to decrease at 60 days. The results of this study showed that beef dry aging at 1 ± 2 °C, relative humidity 78 ± 7 %, ventilation 2.0 m/s for 60 days does not support the growth of L. monocytogenes. On the contrary, the same process supported the growth of Y. enterocolitica up to 40 days in two of the three tested batches, showing that the impact of dry aging on the behaviour of this pathogen deserves further studies.