Mycobiota contaminating some market cake samples with reference to their toxin and enzyme.

Fungi can spoil the majority of baked products. Spoilage of cake during storage is commonly associated with fungi. Therefore, this study aimed to assess the quality of different types of cakes sold in the market. The most predominant fungal genera in the tested cake samples (14 samples) were Aspergillus spp., and Penicillium spp. On Potato Dextrose Agar (PDA), the medium fungal total count was 43.3 colonies /g. Aspergillus was the most dominant genus and was isolated from six samples of cake. Aspergillus was represented by 3 species namely, A. flavus, A. niger, and A. nidulans, represented by 13.32, 19.99, and 3.33 colonies /g respectively. On Malt Extract Agar (MEA) Medium, the fungal total count was 123.24 colonies / g. Aspergillus was the most dominant isolated genus from 11 samples of cake and was represented by 5 species, namely, A. flavus, A. niger, A. ochraceous, A. terreus, and A. versicolor (26. 65, 63.29, 3.33, 6.66, and 3.33 colonies / g , respectively). Twenty-four isolates (88.88 %) of the total tested twenty-seven filamentous fungi showed positive results for amylase production. Ten isolates (37.03%) of the total tested filamentous fungi showed positive results for lipase production, and finally eleven isolates (40.74 %) of the total fungal isolates showed positive results for protease production. Aflatoxins B1, B2, G1, G2, and ochratoxin A were not detected in fourteen collected samples of cake. In this study, clove oil was the best choice overpeppermint oil and olive oil for preventing mold development when natural agents were compared. It might be due to the presence of a varietyof bioactive chemical compounds in clove oil, whose major bioactive component is eugenol, which acts as an antifungal reagent. Therefore, freshly baked cake should be consumed within afew days to avoid individuals experiencing foodborne illnesses.

Genomic characterization of Pseudomonas spp. on food: implications for spoilage, antimicrobial resistance and human infection.

BACKGROUND: Pseudomonas species are common on food, but their contribution to the antimicrobial resistance gene (ARG) burden within food or as a source of clinical infection is unknown. Pseudomonas aeruginosa is an opportunistic pathogen responsible for a wide range of infections and is often hard to treat due to intrinsic and acquired ARGs commonly carried by this species. This study aimed to understand the potential role of Pseudomonas on food as a reservoir of ARGs and to assess the presence of potentially clinically significant Pseudomonas aeruginosa strains on food. To achieve this, we assessed the genetic relatedness (using whole genome sequencing) and virulence of food-derived isolates to those collected from humans. RESULTS: A non-specific culturing approach for Pseudomonas recovered the bacterial genus from 28 of 32 (87.5%) retail food samples, although no P. aeruginosa was identified. The Pseudomonas species recovered were not clinically relevant, contained no ARGs and are likely associated with food spoilage. A specific culture method for P. aeruginosa resulted in the recovery of P. aeruginosa from 14 of 128 (11%) retail food samples; isolates contained between four and seven ARGs each and belonged to 16 sequence types (STs), four of which have been isolated from human infections. Food P. aeruginosa isolates from these STs demonstrated high similarity to human-derived isolates, differing by 41-312 single nucleotide polymorphisms (SNPs). There were diverse P. aeruginosa collected from the same food sample with distinct STs present on some samples and isolates belonging to the same ST differing by 19-67 SNPs. The Galleria mellonella infection model showed that 15 of 16 STs isolated from food displayed virulence between a low-virulence (PAO1) and a high virulence (PA14) control. CONCLUSION: The most frequent Pseudomonas recovered from food examined in this study carried no ARGs and are more likely to play a role in food spoilage rather than infection. P. aeruginosa isolates likely to be able to cause human infections and with multidrug resistant genotypes are present on a relatively small but still substantial proportions of retail foods examined. Given the frequency of exposure, the potential contribution of food to the burden of P. aeruginosa infections in humans should be evaluated more closely.

Evaluating the efficacy of a phage cocktail against Pseudomonas fluorescens group strains in raw milk: microbiological, physical, and chemical analyses.

The objective of this study was to investigate the effectiveness of a phage cocktail against Pseudomonas fluorescens group and its effect on the microbial, physical and chemical properties of raw milk during different storage conditions. A phage cocktail consisting of Pseudomonas fluorescens, Pseudomonas tolaasii, and Pseudomonas libanensis phages was prepared. As a result, reductions in fluorescent Pseudomonas counts of up to 3.44 log units for the storage at 4 °C and 2.38 log units for the storage at 25 °C were achieved. Following the phage application, it is found that there was no significant difference in the total mesophilic aerobic bacteria and Enterobacteriaceae counts. However, it was observed that the number of lactic acid bacteria was higher in phage-treated groups. The results also showed that pH values in the phage added groups were lower than the others and the highest titratable acidity was obtained only in the bacteria-inoculated group. As a future perspective, this study suggests that, while keeping the number of target microorganisms under control in the milk with the use of phages during storage, the microbiota and accordingly the quality parameters of the milk can be affected. This work contributes to the development of effective strategies for maintaining the quality and extending the shelf life of milk and dairy products.

Pseudomonas kulmbachensis sp. nov. and Pseudomonas paraveronii sp. nov., originating from chilled beef and chicken breast.

By investigating wet and dry age-related ripening of beef, Pseudomonas strains V3/3/4/13T and V3/K/3/5T were isolated. Strain V3/3/4/13T exhibited more than 99 % 16S rRNA gene-based similarity to Pseudomonas fragi and other members of this group, while isolate V3/K/3/5T was very close to Pseudomonas veronii and a number of relatives within the Pseudomonas fluorescens group. Additional comparisons of complete rpoB sequences and draft genomes allowed us to place isolate V3/3/4/13T close to Pseudomonas deceptionensis DSM 26521T. In the case of V3/K/3/5T the closest relative was P. veronii DSM 11331T. Average nucleotide identity (ANIb) and digital DNA-DNA hybridization (dDDH) values calculated from the draft genomes of V3/3/4/13T and P. deceptionensis DSM 26521T were 88.5 and 39.8 %, respectively. For V3/K/3/5T and its closest relative P. veronii DSM 11331T, the ANIb value was 95.1 % and the dDDH value was 60.7 %. The DNA G+C contents of V3/3/4/13T and V3/K/3/5T were 57.4 and 60.8 mol%, respectively. Predominant fatty acids were C16 : 0, C18 : 1 ω7c, C17 : 0 cyclo and summed feature C16 : 1 ω7ct/C15 : 0 iso 2OH. The main respiratory quinones were Q9, with minor proportions of Q8 and, in the case of V3/K/3/5T, additional Q10. The main polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and, in the case of V3/K/3/5T, additional phosphatidylcholine. Based on the combined data, isolates V3/3/4/13T and V3/K/3/5T should be considered as representatives of two novel Pseudomonas species. The type strain of the newly proposed Pseudomonas kulmbachensis sp. nov. is V3/3/4/13T (=DSM 113654T=LMG 32520T), a second strain belonging to the same species is FLM 004-28 (=DSM 113604=LMG 32521); the type strain for the newly proposed Pseudomonas paraveronii sp. nov. is V3/K/3/5T (=DSM 113573T=LMG 32518T) with a second isolate FLM 11 (=DSM 113572=LMG 32519).

Nanozyme catalysis pressure-powered intuitive distance variation for portable quantitative detection of H2S with the naked eye.

As a representative gas of food spoilage, the development of rapid hydrogen sulfide (H2S) analysis strategies for food safety control is in great demand. Despite traditional methods for H2S detection possessing great achievements, they are still incapable of meeting the requirement of portability and quantitative detection at the same time. Herein, a nanozyme catalysis pressure-powered sensing platform that enables visual quantification with the naked eye is proposed. In this methodology, Pt nanozyme inherits the catalase-like activity to facilitate the decomposition of H2O2 to O2, which can significantly improve the pressure in the closed container, further pushing the movement of indicator dye. Furthermore, H2S was found to effectively inhibit the catalytic activity of Pt nanozyme, indicating that the catalase-like activity of PtNPs may be regulated by varying concentrations of H2S. Therefore, by utilizing a self-designed pressure-powered microchannel device, the concentration of H2S was successfully converted into a distinct signal variation in distance. The effectiveness of the as-designed sensor in assessing the spoilage of red wine by H2S determination has been demonstrated. It exhibits a strong correlation between the change in dye distance and H2S concentration within the range of 1-250 µM, with a detection limit of 0.17 µM. This method is advantageous as it enhances the quantitative detection of H2S with the naked eye based on the portable pressure-powered sensing platform, as compared to traditional H2S biosensors. Such a pressure-powered distance variation platform would greatly broaden the application of H2S-based detection in food spoilage management.

Prunus persica leaves aqueous extract mediated biosynthesis of Ag nanoparticles and assessment of its anti-quorum sensing potential against Hafnia species.

Hafnia sp. was one of the specific spoilage bacteria in aquatic products, and the aim of the study was to investigate the inhibition ability of the silver nanoparticles (AgNPs) biosynthesis by an aqueous extract of Prunus persica leaves toward the spoilage-related virulence factors of Hafnia sp. The synthesized P-AgNPs were spherical, with a mean particle size of 36.3 nm and zeta potential of 21.8 ± 1.33 mV. In addition, the inhibition effects of P-AgNPs on the growth of two Hafnia sp. strains and their quorum sensing regulated virulence factors, such as the formation of biofilm, secretion of N-acetyl-homoserine lactone (AHLs), proteases, and exopolysaccharides, as well as their swarming and swimming motilities were evaluated. P-AgNPs had a minimum inhibitory concentration (MIC) of 64 µg ml-1 against the two Hafnia sp. strains. When the concentration of P-AgNPs was below MIC, it could inhibit the formation of biofilms by Hafnia sp at 8-32 µg ml-1, but it promoted the formation of biofilms by Hafnia sp at 0.5-4 µg ml-1. P-AgNPs exhibited diverse inhibiting effects on AHLs and protease production, swimming, and swarming motilities at various concentrations.

Development of a quantitative microbiological spoilage risk assessment (QMSRA) model for cooked ham sliced at retail.

A quantitative microbiological spoilage risk assessment model (QMSRA) for cooked ham sliced at retail was developed based on a stochastic growth model for lactic acid bacteria (LAB), which are considered as the specific spoilage organisms (SSO), and a "spoilage-response" relationship characterizing the variability in consumer's perception of spoilage. In a simulation involving 10,000 cooked ham purchases, the QMSRA model predicted a median of zero spoilage events for up to 4.5 days of storage. After storage times of 5 and 6 days, the model predicted 1,790 and 8,570 spoilage events, respectively. A sensitivity analysis showed that domestic storage temperature was the most significant factor affecting LAB concentration in cooked ham, followed by the LAB contamination level at slicing. A scenario analysis was performed testing better temperature control of consumer's refrigerators, better hygiene conditions during slicing and a combination of the two strategies. Among the tested scenarios, a 2 log reduction in the LAB contamination at slicing combined with a 2 °C decrease in domestic storage temperature resulted in zero risk of spoilage for up to 12 days of storage. The QMSRA model developed in the present study can be a useful tool for quality management decisions.

Heat resistance of five spoilage microorganisms in a carbonated broth.

Despite their acidic pH, carbonated beverages can be contaminated by spoilage microorganisms. Thermal treatments, before and/or after carbonation, are usually applied to prevent the growth of these microorganisms. However, the impact of CO2 on the heat resistance of spoilage microorganisms has never been studied. A better understanding of the combined impact of CO2 and pH on the heat resistance of spoilage microorganisms commonly found in carbonated beverages might allow to optimize thermal treatment. Five microorganisms were selected for this study: Alicyclobacillus acidoterrestris (spores), Aspergillus niger (spores), Byssochlamys fulva (spores), Saccharomyces cerevisiae (vegetative cells), and Zygosaccharomyces parabailii (vegetative cells). A method was developed to assess the impact of heat treatments in carbonated media on microbial resistance. The heat resistances of the five studied species are coherent with the literature, when data were available. However, neither the dissolved CO2 concentration (from 0 to 7 g/L), nor the pH (from 2.8 to 4.1) have an impact on the heat resistance of the selected microorganisms, except for As. niger, for which the presence of dissolved CO2 reduced the heat resistance. This study improved our knowledge about the heat resistance of some spoilage microorganisms in presence of CO2.

Comparison of SYBR® Green qPCR assay and plate count method to describe growth of Weissella viridescens and Leuconostoc mesenteroides in pure and mixed cultivation.

The current study was conducted to statistically compare the SYBR® Green quantitative polymerase chain reaction (qPCR) assay and the conventional plate counting (PC) method to construct growth curves of a cocktail of Weissella viridescens in pure culture under different isothermal storage conditions (4, 8, 14, and 30 °C) and in mixed culture with Leuconostoc mesenteroides at 8 °C. The efficiency and specificity of the qPCR standard curves were confirmed, and both methods were adequate to quantify the growth kinetics of W. viridescens at all isothermal temperatures, demonstrating a good correlation and agreement. The efficiencies of the standard curves varied between 98% and 102%. The SYBR® Green qPCR assay was also able to differentiate the growth curves of W. viridescens and L. mesenteroides in the mixed culture at 8 °C. Additionally, the SYBR® Green qPCR method was considered a faster and more sensitive alternative to construct growth curves under different isothermal conditions and differentiate morphologically similar lactic acid bacteria. Overall, the results suggest that the SYBR® Green qPCR method is a reliable and efficient tool to study microbial growth kinetics in pure and mixed cultures.

Biofilm formation of Hafnia paralvei induced by c-di-GMP through facilitating bcsB gene expression promotes spoilage of Yellow River carp (Cyprinus carpio).

Hafnia paralvei, a Gram-negative foodborne pathogen, is found ubiquitously in various aquatic animals and seafoods, which can form biofilm as a dominant virulence factor that contributes to its pathogenesis. However, the biofilm formation mechanism of H. paralvei and its effect on food spoilage has not been fully characterized. Here we show that biofilm formation, is regulated by c-di-GMP which mediated by bcsB, can increase the spoilage ability of H. paralvei. We found that GTP was added exogenously to enhance the synthesis of c-di-GMP, which further promoted biofilm formation. The gene dgcC, one of 11 genes encoding GGDEF domain-containing proteins in H. paralvei, was significantly upregulated with GTP as substrate. The upregulation of dgcC contributes to a significant increase of c-di-GMP and the formation of biofilm. In addition, the overexpression of dgcC induced upregulation of bcsB, a reported effector protein encoding gene, which was further demonstrated that overexpression of bcsB can encourage the synthesis of bacterial cellulose and biofilm formation. The effect of biofilm formation induced by c-di-GMP on spoilage of Yellow River carp (Cyprinus carpio) was evaluated by sensory evaluation, the total viable count, and the total volatile basic nitrogen, which showed that biofilm formation can significantly increase the spoilage ability of H. paralvei on C. carpio. Our findings provide the regulation of c-di-GMP on expression of bcsB, that can contribute to biofilm formation and spoilage ability of H. paralvei, which is favor to understanding the pathogenesis of Hafnia paralvei and its role in food spoilage.

The luxS deletion reduces the spoilage ability of Shewanella putrefaciens: An analysis focusing on quorum sensing and activated methyl cycle.

The luxS mutant strains of Shewanella putrefaciens (SHP) were constructed to investigate the regulations of gene luxS in spoilage ability. The potential regulations of AI-2 quorum sensing (QS) system and activated methyl cycle (AMC) were studied by analyzing the supplementation roles of key circulating substances mediated via luxS, including S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), methionine (Met), homocysteine (Hcy) and 4,5-dihydroxy-2,3-pentanedione (DPD). Growth experiments revealed that the luxS deletion led to certain growth limitations of SHP, which were associated with culture medium and exogenous additives. Meanwhile, the decreased biofilm formation and diminished hydrogen sulfide (H2S) production capacity of SHP were observed after luxS deletion. The relatively lower total volatile base nitrogen (TVB-N) contents and higher sensory scores of fish homogenate with luxS mutant strain inoculation also indicated the weaker spoilage-inducing effects after luxS deletion. However, these deficiencies could be offset with the exogenous supply of circulating substances mentioned above. Our findings suggested that the luxS deletion would reduce the spoilage ability of SHP, which was potentially attributed to the disorder of AMC and AI-2 QS system.

Time and temperature abuse of milk in conditions representing a school cafeteria share table does not meaningfully reduce microbial quality.

Share tables (ST) are tables or stations in school cafeterias where students can return unopened foods and beverages, providing an opportunity to access these items at no cost. Currently, research suggests that milk is among the most wasted items in breakfast and lunch programs in the United States. Share tables present a simple solution for reducing milk waste, but research is needed to understand the microbial spoilage potential of milk in ST. To this end, uninoculated milk cartons and milk cartons inoculated with 2 to 3 log10(cfu/mL) Pseudomonas poae, a fast-growing psychrotroph, was exposed to ambient temperature during winter (mean temperature = 20.3°C) and summer (23.1°C) for 125 min, repeated over 5 d (the length of a school week). Microbial counts in the inoculated milk cartons increased linearly, exceeding the spoilage threshold of 6.0 log10(cfu/mL) after d 3 and after d 4 in the winter and summer season trials, respectively. In the winter trial, the microbial counts for uninoculated milk cartons never exceeded the lower limit of detection, 2.31 log10(cfu/mL), and in the summer trials, microbial counts never reached the spoilage threshold, indicating that initial contamination is a driving factor of microbial milk spoilage. Regardless of sharing status or seasonality, the greatest changes in counts for inoculated milk cartons occurred during overnight refrigeration, ranging from 0.56 to 1.4 log10(cfu/mL), while during the share table ranged from no observable change up to 0.29 log10(cfu/mL), emphasizing that school nutrition personnel should focus efforts on tightly controlling refrigeration temperatures and returning milk to refrigeration as soon as possible. A previously developed model for school cafeteria share tables was adapted to understand the typical residence time of milk in a simulated cafeteria with an ambient temperature share table for the summer and winter seasons over 1,000 wk. Milk was predicted to have a very short mean residence time (85 min) regardless of sharing status or season, with 99.8% of milk consumed, discarded, or donated within the first 2 d. As a result, only 3 out of 451,410 and 6 out of 451,410 simulated milks spoiled in the winter and summer seasons, respectively. The data generated here can be used to inform science-based decision-making for including milk in share tables, or applied to any system where one might have to accept short-term unrefrigerated storage of milk to meet a waste reduction or food security goal.

Phenotypic and genomic characterizations of Klebsiella pneumoniae ssp. pneumoniae and Rahnella inusitata strains reveal no clear association between genetic content and ropy phenotype.

Ropy defect of pasteurized fluid milk is a type of spoilage which manifests itself by an increased viscosity, slimy body, and string-like flow during pouring. This defect has, among other causes, been attributed to the growth, proliferation and exopolysaccharide production by coliform bacteria, which are most commonly introduced in milk as post-pasteurization contaminants. As we identified both Klebsiella pneumoniae ssp. pneumoniae and Rahnella inusitata that were linked to a ropy defect, the goal of this study was to characterize 3 K. pneumoniae ssp. pneumoniae strains and 2 R. inusitata for (1) their ability to grow and cause ropy defect in milk at 6°C and 21°C and to (2) probe the genetic basis for observed ropy phenotype. Although all K. pneumoniae ssp. pneumoniae and R. inusitata strains showed net growth of >4 log10 over 48 h in UHT milk at 21°C, only R. inusitata strains displayed growth during 28-d incubation period at 6°C (>6 log10). Two out of 3 K. pneumoniae ssp. pneumoniae strains were capable of causing the ropy defect in milk at 21°C, as supported by an increase in the viscosity of milk and string-like flow during pouring; these 2 strains were originally isolated from raw milk. Only one R. inusitata strains was able to cause the ropy defect in milk; this strain was able to cause the defect at both 6°C and 21°C, and was originally isolated from a pasteurized milk. These findings suggest that the potential of K. pneumoniae ssp. pneumoniae and R. inusitata to cause ropy defect in milk is a strain-dependent characteristic. Comparative genomics provided no definitive answer on genetic basis for the ropy phenotype. However, for K. pneumoniae ssp. pneumoniae, genes rffG, rffH, rfbD, and rfbC involved in biosynthesis and secretion of enterobacterial common antigen (ECA) could only be found in the 2 strains that produced ropy defect, and for R. inusitata a set of 2 glycosyltransferase- and flippase genes involved in nucleotide sugar biosynthesis and export could only be identified in the ropy strain. Although these results provide some initial information for potential markers for strains that can cause ropy milk, the relationship between genetic content and ropiness in milk remains poorly understood and merits further investigation.

Identification and Characterization of Microorganisms Isolated from Non-compliant and/or Atypical Dairy Products in Canada.

Despite good manufacturing practices and rigorous cleaning and sanitizing procedures established in dairy processing plants, microbiological contamination remains the main cause of products being non-compliant and/or atypical and hence not fit for human consumption. The objective of this study was to isolate, identify and characterize bacteria, yeasts and molds associated with substandard dairy products in Canada and to create a collection of reference isolates. In addition to conventional microbiological characterization, each isolate was tested for biofilm-forming ability and susceptibility to heat, antimicrobial agents, and common industrial disinfectants. Among the 105 microbial strains isolated from pasteurized milk, cream, and cheese samples, 24 bacterial isolates, belonging mainly to the genus Pseudomonas, were shown to be moderate or strong biofilm producers in 96-well plates and highly resistant to peracetic acid (100 ppm, 5 min contact time) and sodium hypochlorite (70 ppm, 5 min contact time). In addition, 56 bacterial isolates, including Acinetobacter baumannii, Enterobacter bugandensis, Klebsiella pneumoniae and Pseudomonas spp., were found resistant to ampicillin, fosfomycin and/or ceftriaxone, while 14 others, such as Bacillus spp. and Macrococcus spp., withstood a heat treatment equivalent to low-temperature long-time pasteurization (63°C for 30 min). This descriptive study provides new information on potential problematic microorganisms in dairies and will guide the development of novel control strategies intended to prevent and reduce microbiological contamination and the associated economic losses.

Invited review: Role of Bacillus licheniformis in the dairy industry- friends or foes?

Bacillus licheniformis is one of the major spore-forming bacteria with great genotypic diversity in raw milk, dairy ingredients, final dairy products, and is found throughout the dairy processing continuum. Though being widely used as a probiotic strain, this species also serves as a potential risk in the dairy industry based on its roles in foodborne illness and dairy spoilage. Biofilm formation of B. licheniformis in combined with the heat resistance of its spores, make it impossible to prevent the presence of B. licheniformis in final dairy products by traditional cleaning and disinfection procedures. Despite the extensive efforts on the identification of B. licheniformis from various dairy samples, no reviews have been reported on both hazard and benefits of this spore-former. This review discusses the prevalence of B. licheniformis from raw milk to commercial dairy products, biofilm formation and spoilage potential of B. licheniformis, and its potential prevention methods. In addition, the potential benefits of B. licheniformis in the dairy industry were also summarized.

Transparent, flexible, and eco-friendly starch-based films for reversible optoelectronic noses for food spoilage monitoring in smart packaging.

A reversible optoelectronic nose is presented consisting of ten acid-base indicators incorporated into a starch-based film, covering a wide pH range. The starch substrate is odorless, biocompatible, flexible, and exhibits high tensile resistance. This optical artificial olfaction system was used to detect the early stages of food decomposition by exposing it to the volatile compounds produced during the spoialge process of three food products (beef, chicken, and pork). A smartphone was used to capture the color changes caused by intermolecular interactions between each dye and the emitted volatiles over time. Digital images were processed to generate a differential color map, which uses the observed color shifts to create a unique signature for each food product. To effectively discriminate among different samples and exposure times, we employed chemometric tools, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). This approach detects food deterioration in a practical, cost-effective, and user-friendly manner, making it suitable for smart packaging. Additionally, the use of starch-based films in the food industry is preferable due to their biocompatibility and biodegradability characteristics.

Development of a Sensitive Colorimetric Indicator for Detecting Beef Spoilage in Smart Packaging.

This study aimed to fabricate and characterize a novel colorimetric indicator designed to detect ammonia (NH3) and monitor meat freshness. The sensing platform was constructed using electrospun nanofibers made from polylactic acid (PLA), which were then impregnated with anthocyanins as a natural pH-sensitive dye, extracted from red cabbage. This research involved investigating the relationship between the various concentrations of anthocyanins and the colorimetric platform's efficiency when exposed to ammonia vapor. Scanning electron microscope (SEM) results were used to examine the morphology and structure of the nanofiber mats before and after the dip-coating process. The study also delved into the selectivity of the indicator when exposed to various volatile organic compounds (VOCs) and their stability under extreme humidity levels. Furthermore, the platform's sensitivity was evaluated as it encountered ammonia (NH3) in concentrations ranging from 1 to 100 ppm, with varying dye concentrations. The developed indicator demonstrated an exceptional detection limit of 1 ppm of MH3 within just 30 min, making it highly sensitive to subtle changes in gas concentration. The indicator proved effective in assessing meat freshness by detecting spoilage levels in beef over time. It reliably identified spoilage after 10 h and 7 days, corresponding to bacterial growth thresholds (107 CFU/mL), both at room temperature and in refrigerated environments, respectively. With its simple visual detection mechanism, the platform offered a straightforward and user-friendly solution for consumers and industry professionals alike to monitor packaged beef freshness, enhancing food safety and quality assurance.

Designing the pH-sensitive indicator based on starch nanoparticle with bromocresol green for monitoring meat spoilage.

The starch nanoparticle, combined with bromocresol green (BCG), served as a pH-sensitive indicator to monitor meat quality throughout an 8-day refrigerated storage period. The meat samples were sealed in package which the pH-sensitive indicator attached to the interior part of packaging lid. The changes in meat quality were evaluated by total volatile base nitrogen (TVBN), pH, total viable count (TVC), sensory analysis, and color in interval of 0, 3, 5, 7, and 8-days storage at 4°C. Initial TVBN values were recorded at 19.6 mg/100 g, increased to 26.6 mg/100 g by the end of storage period. The pH value was significantly increased after 8 days storage at 4°C. The observed color variation in the indicator from yellow to blue was attributed to the concurrent increases in TVBN, TVC, and pH. The indicator color changes had significant correlation with analyzed chemical quality of stored meat. Therefore, the designed BCG pH-sensitive indicator could be effective in monitoring the meat spoilage during storage.

Revealing the spoilage characteristics of refrigerated prepared beef steak by advanced bioinformatics tools.

BACKGROUND: Although microorganisms are the main cause of spoilage in prepared beef steaks, very few deep spoilage mechanisms have been reported so far. Aiming to unravel the mechanisms during 12 days of storage at 4 °C affecting the quality of prepared beef steak, the present study investigated the changes in microbial dynamic community using a combined high-throughput sequencing combined and bioinformatics. In addition, gas chromatography-mass spectrometry combined with multivariate statistical analysis was utilized to identify marker candidates for prepared steaks. Furthermore, cloud platform analysis was applied to determine prepared beef steak spoilage, including the relationship between microbiological and physicochemical indicators and volatile compounds. RESULTS: The results showed that the dominant groups of Pseudomonas, Brochothrix thermosphacta, Lactobacillus and Lactococcus caused the spoilage of prepared beef steak, which are strongly associated with significant changes in physicochemical properties and volatile organic compounds (furan-2-pentyl-, pentanal, 1-octanol, 1-nonanol and dimethyl sulfide). Metabolic pathways were proposed, among which lipid metabolism and amino acid metabolism were most abundant. CONCLUSION: The present study is helpful with respect to further understanding the relationship between spoilage microorganisms and the quality of prepared beef steak, and provides a reference for investigating the spoilage mechanism of dominant spoilage bacteria and how to extend the shelf life of meat products. © 2024 Society of Chemical Industry.

Improving the microbiological safety and quality of aquatic products using nonthermal processing.

Spoilage and deterioration of aquatic products during storage are inevitable, posing significant challenges to their suitability for consumption and the sustainability of the aquatic products supply chain. Research on the nonthermal processing of fruit juices, probiotics, dairy products, and meat has demonstrated positive outcomes in preserving quality. This review examines specific spoilage bacteria species and mechanisms for various aquatic products and discusses the principles, characteristics, and applications of six nonthermal processing methods for bacterial inhibition to maintain microbiological safety and physicochemical quality. The primary spoilage bacteria groups differ among fish, crustaceans, and shellfish based on storage conditions and durations. Four metabolic pathways utilized by spoilage microorganisms-peptides and amino acids, nitrogen compounds, nucleotides, and carbohydrates-are crucial in explaining spoilage. Nonthermal processing techniques, such as ultrahigh pressure, irradiation, magnetic/electric fields, plasma, and ultrasound, can inactivate microorganisms, thereby enhancing microbiological safety, physicochemical quality, and shelf life. Future research may integrate nonthermal processing with other technologies (e.g., modified atmosphere packaging and omics) to elucidate mechanisms of spoilage and improve the storage quality of aquatic products.