Insights into the Identification of the Specific Spoilage Organisms in Chicken Meat

A Microbiological and Sensory Evaluation of Modified Atmosphere-Packed (MAP) Chicken at Use-By Date and Beyond

Consumers are responsible for a large proportion of food waste, and food that has reached its use-by or best-before date is often discarded, even if edible. In this study on fresh chicken, the suitability of use-by dates currently used in the EU was evaluated by using microbial and sensory analyses. This was carried out by analyzing bacterial populations of chicken breast fillets (M. pectoralis major) at three different time points (use-by date, 2 days past use-by date, 4 days past use-by date) and two different storage temperatures (4 °C, 8 °C). A discrimination triangle test was performed to check for sensory differences between chicken breast fillets cooked at the three selected time points for both storage temperatures. A consumer preference test was also performed for chicken breast fillets that had been stored at the highest recommended temperature (4 °C) and after being cooked at the three time points. Changes in populations of total aerobic count (TAC), Enterobacteriaceae (EB), and lactic acid bacteria (LAB) were recorded over time. Despite large differences in bacterial counts at the selected time points, with TAC populations of approximately 6.5 and 8.0 log CFU/g at use-by date and four days after use-by date, respectively, storage for two or four extra days had no significant effect on the sensory parameters of cooked chicken compared with chicken consumed at its use-by date. Since the TAC populations were close to or above levels that are associated with spoilage, more work is needed to explore if shelf life can be extended.

Next-Generation Sequencing for the Detection of Microbial Agents in Avian Clinical Samples

Direct-targeted next-generation sequencing (tNGS), with its undoubtedly superior diagnostic capacity over real-time PCR (RT-PCR), and direct-non-targeted NGS (ntNGS), with its higher capacity to identify and characterize multiple agents, are both likely to become diagnostic methods of choice in the future. tNGS is a rapid and sensitive method for precise characterization of suspected agents. ntNGS, also known as agnostic diagnosis, does not require a hypothesis and has been used to identify unsuspected infections in clinical samples. Implemented in the form of multiplexed total DNA metagenomics or as total RNA sequencing, the approach produces comprehensive and actionable reports that allow semi-quantitative identification of most of the agents present in respiratory, cloacal, and tissue samples. The diagnostic benefits of the use of direct tNGS and ntNGS are high specificity, compatibility with different types of clinical samples (fresh, frozen, FTA cards, and paraffin-embedded), production of nearly complete infection profiles (viruses, bacteria, fungus, and parasites), production of "semi-quantitative" information, direct agent genotyping, and infectious agent mutational information. The achievements of NGS in terms of diagnosing poultry problems are described here, along with future applications. Multiplexing, development of standard operating procedures, robotics, sequencing kits, automated bioinformatics, cloud computing, and artificial intelligence (AI) are disciplines converging toward the use of this technology for active surveillance in poultry farms. Other advances in human and veterinary NGS sequencing are likely to be adaptable to avian species in the future.

The efficiency of UV light-emitting diodes (UV-LED) in decontaminating Campylobacter and Salmonella and natural microbiota in chicken breast, compared to a UV pilot-plant scale device

This study investigated the combined effect of Ultraviolet (UV) light-emitting diode (LED) technology treatment with refrigerated storage of chicken breast meat over 7 days on Campylobacter jejuni, Salmonella enterica serovar Typhimurium, total viable counts (TVC) and total Enterobacteriaceae counts (TEC). An optimised UV-LED treatment at 280 nm for 6 min decreased inoculated S. Typhimurium and C. jejuni populations by 0.6-0.64 log CFU/g, and TVC and TEC population by 1-1.2 log CFU/g in chicken samples. During a 7-day storage at 4 °C, a 0.73 log reduction in C. jejuni was achieved compared with non-treated samples. Moreover, the UV-LED effectiveness to reduce TVC and TEC during refrigerated storage was compared with a conventional UV lamp and a similar efficiency was observed. The impact of UV-LED and UV lamp devices on the microbial community composition of chicken meat during storage was further examined using 16 S rRNA gene amplicon sequencing. Although similar bacterial reductions were observed for both technologies, the microbial communities were impacted differently. Treatment with the UV conventional lamp increased the proportion of Brochothrix spp. In meat samples, whilst Photobacterium spp. Levels were reduced.

Microbiological Quality and Safety of Fresh Quail Meat at the Retail Level

The objective of this study was to evaluate the microbiological quality and safety of 37 fresh quail meats. Mesophiles, Pseudomonas spp., Enterobacteriaceae, and staphylococci counts were 5.25 ± 1.14, 3.92 ± 1.17, 3.09 ± 1.02, and 2.80 ± 0.64 log CFU/g, respectively. Listeria monocytogenes was detected in seven samples (18.92%). Campylobacter jejuni was detected in one sample (2.70%). Clostridium perfringens was not detected in any sample. The dominant bacteria were Pseudomonas spp. (30.46%), Micrococcaceae (19.87%), lactic acid bacteria (14.57%), and Enterobacteriaceae (11.92%). Brochotrix thermosphacta and enterococci were isolated to a lesser extent, 7.28% and 1.99%, respectively. The dominant Enterobacteriaceae found were Escherichia coli (42.53%). ESBL-producing E. coli was detected in one sample (2.70%), showing resistance to 16 antibiotics. Sixteen different Staphylococcus spp. and three Mammaliicoccus spp. were identified, the most common being S. cohnii (19.86%) and M. sciuri (17.02%). S. aureus and S. epidermidis were also found in one and four samples, respectively. Methicillin-resistant M. sciuri and S. warneri were found in 13.51% and 10.81% of quail samples, respectively. These bacteria showed an average of 6.20 and 18.50 resistances per strain, respectively. The high resistance observed in ESBL-producing E. coli and methicillin-resistant S. warneri is of special concern. Measures should be adopted to reduce the contamination of quail meat.

Quantification of Bioactive Metabolites Derived from Cell-Free Supernatant of Pediococcus acidilactici and Screening their Protective Properties in Frankfurters

The specific aims of the current study were to determine and quantify the bioactive compounds derived from the cell-free supernatant (CFS) of Pediococcus acidilactici and screen their protective effect in frankfurters by applying an edible coating. This was achieved by immersing the peeled frankfurters in the CFS (CFS: 50% and 100%) alone or in combination with chitosan (CH: 0.5% and 1%) solutions for 3 min. Untreated frankfurter samples (control) exceeded the maximum acceptable total viable count limit (7.0 log10) on the 14th day, whereas samples treated with 100% CFS + 1% chitosan reached the limit on day 28 during refrigerated storage (P < 0.05). This treatment provided a 14-day extension to the shelf life of frankfurters without causing any significant changes in color and sensory attributes (P > 0.05). Additionally, this treatment inhibited oxidation in the frankfurters, leading to no significant changes in TBA and TVB-N within this group during storage (P > 0.05). This protective effect was mainly attributed to the wide variety of bioactive compounds identified in the CFS, including a total of 5 organic acids, 20 free amino acids, 11 free fatty acids, 77 volatiles, and 10 polyphenols. Due to these bioactive compounds, CFS exhibited a strong radical scavenging capacity (DPPH: 435.08 TEAC/L, ABTS: 75.01 ± 0.14 mg TEAC/L; FRAP: 1.30 ± 0.03 mM FE/L) and antimicrobial activity against microorganisms primarily responsible for the spoilage of frankfurters. In conclusion, the results indicate that the CFS contains high levels of bioactive metabolites, and an edible chitosan coating impregnated with CFS can be utilized to extend the shelf life of frankfurters through its antimicrobial effects and oxidation stabilization.

Improving the quality of the chicken fillet using chitosan, gelatin, and starch coatings incorporated with bitter orange peel extract during refrigeration

The preserving potential of biopolymer coatings can be improved by adding natural antimicrobial and antioxidant compounds. The objective of this study was to evaluate the effect of natural coatings (gelatin (Gel), chitosan (Ch), and modified starch (MS)) incorporated with bitter orange peel extract (BOE) on the quality of the chicken fillets during cold. BOE had a high amount of phenolic compounds (145.28 mgGAE/g). Coating the fillets with pure BOE exerted a higher inhibitory effect against bacterial growth compared to composite coatings without extract. Lower microbial count (2-3 log CFU/g on days 9 and 12 of storage) was observed in the samples coated with composite biopolymers incorporated with BOE in comparison to the coatings without BOE. Composite coatings of Gel/MS/BOE showed lower FFA in the fillets followed by Gel/Ch/BOE and MS/Ch/BOE. The lowest TVB-N belonged to MS/Ch/BOE followed by Gel/Ch/BOE and Gel/MS/BOE which were 17.05, 17.39, and 19.40 mg/100 g at the end of the storage. Among the samples, pure BOE, Gel/MS/BOE, Gel/Ch/BOE, and MS/Ch/BOE showed the lowest peroxide value and the coatings containing chitosan had a slower rate of hydroperoxide generation. Drip loss showed a descending trend in all coated samples except for an enhancement in control and BOE-coated fillets, 6.42% and 6.39%, respectively, on day 12 of storage. Samples coated with Gel/MS and Gel/MS/BOE had the lowest drip loss during the storage period (5.96% and 5.98%, respectively). It should be noted that coatings containing chitosan had higher antimicrobial and antioxidant effects. The effect of the coatings as antimicrobial barriers and preservative agents were as follows: Gel/Ch/BOE > MS/Ch/BOE > Gel/MS/BOE. It can be concluded that the applied composite coatings in this work have a high potential to maintain and improve the quality of raw chicken fillets during storage in the refrigerator.

Quantitative microbiological spoilage risk assessment (QMSRA) of fresh poultry fillets during storage at retail

A quantitative microbiological spoilage risk assessment model (QMSRA) of aerobically stored fresh poultry fillets was developed based on pseudomonads growth and metabolic activity. Simultaneous microbiological and sensory analyses were performed in poultry fillets to evaluate the relation between pseudomonads concentration and sensory rejection due to spoilage. The analysis showed no organoleptic rejection at pseudomonads concentrations less than 6.08 log CFU/cm². For higher concentrations, a "spoilage-response" relationship was developed using a beta-Poisson model. The above relationship was combined with a stochastic modeling approach for pseudomonads growth by taking into account both variability and uncertainty of factors affecting spoilage. To enhance the reliability of the developed QMSRA model, uncertainty was quantified and separated from variability using a second order Monte Carlo simulation. For a batch of 10,000 units, the QMSRA model predicted a median number of 11, 80, 295, 733 and 1,389 spoiled units for retail storage times of 6,7, 8, 9 and 10 days, respectively, while no spoiled units were predicted for storage time of up to 5 days at retail. Scenario analysis showed that a reduction of 1 log in the pseudomonads concentration at the time of packaging or 1 °C in retail storage temperature results in up to 90% reduction of the spoiled units while the combination of the above interventions can reduce the risk of spoilage by up to 99%, depending on the storage time. The poultry industry can utilize the QMSRA model as a transparent scientific basis to support food quality management decisions in determining appropriate expiration dates which maximize the utilization of the product's "true" shelf life while minimize the risk of spoilage to an acceptable level. Furthermore, the scenario analysis can provide the necessary components for an effective cost-benefit analysis, enabling the identification and comparison of appropriate strategies for extending the shelf life of fresh poultry products.

Preparation of Nanopaper for Colorimetric Food Spoilage Indication

In this study, we are reporting the fabrication of a nanocellulose (NFC) paper-based food indicator for chicken breast spoilage detection by both visual color change observation and smartphone image analysis. The indicator consists of a nanocellulose paper (nanopaper) substrate and a pH-responsive dye, bromocresol green (BCG), that adsorbs on the nanopaper. The nanopaper is prepared through vacuum filtration and high-pressure compression. The nanopaper exhibits good optical transparency and strong mechanical strength. The color change from yellow to blue in the nanopaper indicator corresponding to an increase in the solution pH and chicken breast meat storage data were observed and analyzed, respectively. Further, we were able to use color differences determined by the RGB values from smartphone images to analyze the results, which indicates a simple, sensitive, and readily deployable approach toward the development of future smartphone-based food spoilage tests.

Microbiological Quality and Safety of Fresh Turkey Meat at Retail Level, Including the Presence of ESBL-Producing Enterobacteriaceae and Methicillin-Resistant S. aureus

The aim of this work was to study the microbiological safety and quality of marketed fresh turkey meat, with special emphasis on methicillin-resistant S. aureus, ESBL-producing E. coli, and K. pneumoniae. A total of 51 fresh turkey meat samples were collected at retail level in Spain. Mesophile, Pseudomonas spp., enterococci, Enterobacteriaceae, and staphylococci counts were 5.10 ± 1.36, 3.17 ± 0.87, 2.03 ± 0.58, 3.18 ± 1.00, and 2.52 ± 0.96 log CFU/g, respectively. Neither Campylobacter spp. nor Clostridium perfringens was detected in any sample. ESBL-producing K. pneumoniae and E. coli were detected in 22 (43.14%), and three (5.88%) samples, respectively, all of which were multi-resistant. Resistance to antimicrobials of category A (monobactams, and glycilcyclines) and category B (cephalosporins of third or fourth generation, polymixins, and quinolones), according to the European Medicine Agency classification, was found among the Enterobacteriaceae isolates. S. aureus and methicillin-resistant S. aureus were detected in nine (17.65%) and four samples (7.84%), respectively. Resistance to antimicrobials of category A (mupirocin, linezolid, rifampicin, and vancomycin) and category B (cephalosporins of third- or fourth generation) was found among S. aureus, coagulase-negative staphylococci, and M. caseolyticus isolates.

Bio-preservation Effect of Probiotic Lactiplantibacillus plantarum S61 Against Rhodotorula glutinis and Listeria monocytogenes in Poultry Meat

The objective of this work is the study of the antifungal and antibacterial activity of Lactiplantibacillus plantarum S61 strains, isolated from traditional fermenting green olives against Rhodotorula glutinis UMP 22 and Listeria monocytogenes ATCC 19117, and its application in meat as bio-preservative agent. The cell-free supernatant (CFS) of Lpb. plantarum S61 shows high inhibition zones, which are 22.45 ± 0.49 and 17.75 ± 0.35 mm, against Rhodotorula glutinis and Listeria monocytogenes. The minimum fungicidal and bactericidal concentrations of the CFS obtained are 8% (v/v) and 10% (v/v), respectively. The competition assay, realized in liquid medium by co-culture of Lpb. plantarum S61 with Rho Rhodotorula glutinis and L. monocytogenes, led to inhibition percentages of 77.72% and 89.52%, respectively. However, the antimicrobial activity of Lpb. plantarum S61 was revealed a proteinaceous nature. Lpb. plantarum S61 strain allowed the reduction of L. monocytogenes in minced poultry meat during 7 days of storage at 4 °C. In addition, Lpb. plantarum S61 improved the physicochemical and color parameters of poultry minced meat. Lpb. plantarum S61 and/or its antimicrobial compounds can be applied as bio-preservative agent in meat product and food industry.

Critical review and recent advances of 2D materials-Based gas sensors for food spoilage detection

Many people around the world are concerned about meat safety and quality, which has resulted in the ongoing advancement of packaged food technology. Since the emergence of graphene in 2004, the number of studies on layered two-dimensional materials (2DMs) for applications ranging from food packaging to meat quality monitoring has been expanding quickly. Recently, scientists have been working hard to develop a novel class of 2DMs that keep the good things about graphene but don't have zero bandgaps at room temperature. Much work has been done on layered transition metal dichalcogenides (TMDCs) like different metal sulfides and selenides for meat spoilage gas sensors. This review looks at (i) the main indicators of meat spoilage and (ii) the detection methods that can be used to find out if meat has been spoiled, such as chemiresistive, electrochemical, and optical methods. (iii) the role of 2DMs in meat spoilage detection and (iv) the emergence of advanced methods for selective classification of target analytes in meat/food spoilage detection in recent years. Thus, this review demonstrates the potential scope of 2DMs for developing intelligent sensor systems for food and meat spoilage detection with high viability, simplicity, cost-effectiveness, and other multipurpose tools.

Development and validation of a mathematical model for pseudomonads growth as a basis for predicting spoilage of fresh poultry breast and thigh fillets

The growth of naturally contaminated pseudomonads on fresh breast and thigh poultry fillets during aerobic storage was studied and modeled as a function of temperature (0–30°C). A statistical comparison of the models for breast and thigh fillets showed that muscle type does not significantly affect the temperature dependence of pseudomonads growth kinetics. A unified model for breast and thigh was developed and validated against pseudomonads growth rate data under isothermal conditions extracted from literature and experimental data under dynamic temperature conditions. The validation results showed a satisfactory performance of the model with the bias and accuracy factors ranging from 0.85 to 1.09 and 1.02 to 1.21, respectively. The model was further used to predict the shelf life of fresh poultry as the time required by pseudomonads to reach the spoilage level for various scenarios of temperature, initial contamination level, and physiological state of pseudomonads demonstrating its application in a risk-based shelf-life assessment of fresh poultry products.

A Comprehensive Evaluation of Enterobacteriaceae Primer Sets for Analysis of Host-Associated Microbiota

Enterobacteriaceae is one of the most important bacterial groups within the Proteobacteria phylum. This bacterial group includes pathogens, commensal and beneficial populations. Numerous 16S rRNA gene PCR-based assays have been designed to analyze Enterobacteriaceae diversity and relative abundance, and, to the best of our knowledge, 16 primer pairs have been validated, published and used since 2003. Nonetheless, a comprehensive performance analysis of these primer sets has not yet been carried out. This information is of particular importance due to the recent taxonomic restructuration of Enterobacteriaceae into seven bacterial families. To overcome this lack of information, the identified collection of primer pairs (n = 16) was subjected to primer performance analysis using multiple bioinformatics tools. Herein it was revealed that, based on specificity and coverage of the 16S rRNA gene, these 16 primer sets could be divided into different categories: Enterobacterales-, multi-family-, multi-genus- and Enterobacteriaceae-specific primers. These results highlight the impact of taxonomy changes on performance of molecular assays and data interpretation. Moreover, they underline the urgent need to revise and update the molecular tools used for molecular microbial analyses.

The Potential Effect of Microbiota in Predicting The Freshness of Chilled Chicken

1. The goals of this study were to analyse the changes in microbiota composition of chilled chicken during storage and identify microbial biomarkers related to meat freshness.2. The study used 16S rDNA sequencing to track the microbiota shift in chilled chicken during storage. Associations between microbiota composition and storage time were analysed and microbial biomarkers were identified.3. The results showed that microbial diversity of chilled chicken decreased with the storage time. A total of 27 and 24 microbial biomarkers were identified by using orthogonal partial least squares (OPLS) and the random forest regression approach, respectively. The receiver operating characteristic (ROC) curve analysis indicated that the OPLS regression approach had better performance in identifying freshness-related biomarkers. The multiple stepwise regression analysis identified four key microbial biomarkers, including Streptococcus, Carnobacterium, Serratia and Photobacterium genera and constructed a predictive model.4. The study provided microbial biomarkers and a model related to the freshness of chilled chicken. These findings provide a basis for developing detection methods of the freshness of chilled chicken.

Identification of the Specific Spoilage Organism in Farmed Sturgeon (Acipenser baerii) Fillets and Its Associated Quality and Flavour Change during Ice Storage

Hybrid sturgeon, a popular commercial fish, plays important role in the aquaculture in China, while its spoilage during storage significantly limits the commercial value. In this study, the specific spoilage organisms (SSOs) from ice stored-sturgeon fillet were isolated and identified by analyzing their spoilage related on sensory change, microbial growth, and biochemical properties, including total volatile base nitrogen (TVBN), thiobarbituric acid reactive substances (TBARS), and proteolytic degradation. In addition, the effect of the SSOs on the change of volatile flavor compounds was evaluated by solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The results showed that the Pseudomonas fluorescens, Pseudomonas mandelii, and Shewanella putrefaciens were the main SSOs in the ice stored-sturgeon fillet, and significantly affect the odors by changing the volatile compounds in the sturgeon. Compared with the fresh sturgeon, the appreciable increase of polycyclic aromatic hydrocarbons and tetramethyl-pyrazine might be the spoilage indicators of the sturgeon contaminated by P. fluorescens; the appreciable increase of 1-octen-3-ol and (z)-2-penten-1-o might be the potential marker of the sturgeon contaminated by P. mandelii; and the appreciable increase of 1-(3,3-dimethylbicyclo [2.2.1] hept-2-yl)-ethanon and butylated hydroxytoluene were associated with S. putrefaciens. This study reveals the relationship between the SSOs and flavor changes in sturgeon fillets, which will contribute to the sturgeon preservation and shelf-life extension.

Characterization of Pediococcus acidilactici postbiotic and impact of postbiotic-fortified chitosan coating on the microbial and chemical quality of chicken breast fillets

This study was carried out to characterize antioxidant activity, total phenolic content, and the phenolic and flavonoids profile of postbiotic of Pediococcus acidilactici and to evaluate the effects of postbiotics (10% and 50%) alone and in combination with chitosan coating (1%) on the microbial and chemical quality of chicken breast fillets during storage at 4 °C. Antioxidant activity and total phenolic content of the postbiotics were found to be 1291.02 ± 1.5 mg/L TEAC and 2336.11 ± 2.36 mg/L GAE, respectively. The most abundant phenolic was vanillic acid, followed by t-caffeic, gallic, and caftaric acids. The postbiotic-chitosan (50% + 1%) combination decreased L. monocytogenes and S. Typhimurium counts by 1.5 and 2.1 log₁₀ CFU/g, respectively, compared to the control (P < 0.05). This combination decreased the total viable count (TVC), lactic acid bacteria (LAB), and psychrotrophic bacteria count compared to the control (P < 0.05). No differences were found in thiobarbituric acid (TBA) values among the samples during storage (P > 0.05). Postbiotic treatment did not significantly change the pH values and color properties of the breast fillets (P > 0.05). Postbiotic-chitosan combinations extended the shelf-life by up to 12 days compared to the control. In conclusion, the postbiotic-chitosan combination can be used to preserve and improve the microbial quality of chicken meat products.

Total volatile basic nitrogen and trimethylamine in muscle foods: Potential formation pathways and effects on human health

The use of total volatile basic nitrogen (TVB-N) as a quality parameter for fish is rapidly growing to include other types of meat. Investigations of meat quality have recently focused on TVB-N as an index of freshness, but little is known on the biochemical pathways involved in its generation. Furthermore, TVB-N and methylated amines have been reported to exert deterimental health effects, but the relationship between these compounds and human health has not been critically reviewed. Here, literature on the formative pathways of TVB-N has been reviewed in depth. The association of methylated amines and human health has been critically evaluated. Interventions to mitigate the effects of TVB-N on human health are discussed. TVB-N levels in meat can be influenced by the diet of an animal, which calls for careful consideration when using TVB-N thresholds for regulatory purposes. Bacterial contamination and temperature abuse contribute to significant levels of post-mortem TVB-N increases. Therefore, controlling spoilage factors through a good level of hygiene during processing and preservation techniques may contribute to a substantial reduction of TVB-N. Trimethylamine (TMA) constitutes a significant part of TVB-N. TMA and trimethylamine oxide (TMA-N-O) have been related to the pathogenesis of noncommunicable diseases, including atherosclerosis, cancers, and diabetes. Proposed methods for mitigation of TMA and TMA-N-O accumulation are discussed, which include a reduction in their daily dietary intake, control of internal production pathways by targeting gut microbiota, and inhibition of flavin monooxygenase 3 enzymes. The levels of TMA and TMA-N-O have significant health effects, and this should, therefore, be considered when evaluating meat quality and acceptability. Agreed international values for TVB-N and TMA in meat products are required. The role of feed, gut microbiota, and translocation of methylated amines to muscles in farmed animals requires further investigation.

Characterization of chilled chicken spoilage using an integrated microbiome and metabolomics analysis

Spoilage of chilled chicken can occur as a result of microbial development and consumption of meat nutrients by spoilage bacteria, ultimately resulting in the release of undesired metabolites. Characterizing the profiles of the microbiota and metabolites and clarifying their relationships will contribute to an improved understanding of the mechanism underlying chilled chicken spoilage. In the present study, 16S rRNA gene sequencing and ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS)-based untargeted metabolomics analyses were applied to determine the microbial and metabolic profiles in chicken during chilled storage. The microbial and metabolic datasets were subjected to combined analysis using weighted gene co-expression network analysis (WGCNA) and Spearman's correlation analysis. Brochothrix, Carnobacterium, Photobacterium, Pseudomonas, Acinetobacter, Serratia, Kurthia, Shewanella, and Obesumbacterium genera were identified as the dominant spoilage bacteria in chilled chicken. Ten metabolic pathways, including histidine metabolism and purine metabolism, were identified as potential mechanisms underlying chilled chicken spoilage. Correlation analysis demonstrated that spoilage bacterial genera were highly correlated with spoilage-related metabolites. Taken together, the present study proposed an integrated microbiome and metabolomics approach to investigate the mechanism of chilled chicken spoilage caused by microbial activity. The results obtained by this approach provide a comprehensive insight into changes in the microbial and metabolic profiles of chilled chicken during spoilage.

Rapid Microbial Quality Assessment of Chicken Liver Inoculated or Not With Salmonella Using FTIR Spectroscopy and Machine Learning

Chicken liver is a highly perishable meat product with a relatively short shelf-life and that can get easily contaminated with pathogenic microorganisms. This study was conducted to evaluate the behavior of spoilage microbiota and of inoculated Salmonella enterica on chicken liver. The feasibility of Fourier-transform infrared spectroscopy (FTIR) to assess chicken liver microbiological quality through the development of a machine learning workflow was also explored. Chicken liver samples [non-inoculated and inoculated with a four-strain cocktail of ca. 10³ colony-forming units (CFU)/g Salmonella] were stored aerobically under isothermal (0, 4, and 8°C) and dynamic temperature conditions. The samples were subjected to microbiological analysis with concomitant FTIR measurements. The developed FTIR spectral analysis workflow for the quantitative estimation of the different spoilage microbial groups consisted of robust data normalization, feature selection based on extra-trees algorithm and support vector machine (SVM) regression analysis. The performance of the developed models was evaluated in terms of the root mean square error (RMSE), the square of the correlation coefficient (R²), and the bias (B_f) and accuracy (A_f) factors. Spoilage was mainly driven by Pseudomonas spp., followed closely by Brochothrix thermosphacta, while lactic acid bacteria (LAB), Enterobacteriaceae, and yeast/molds remained at lower levels. Salmonella managed to survive at 0°C and dynamic conditions and increased by ca. 1.4 and 1.9 log CFU/g at 4 and 8°C, respectively, at the end of storage. The proposed models exhibited A_f and B_f between observed and predicted counts within the range of 1.071 to 1.145 and 0.995 to 1.029, respectively, while the R² and RMSE values ranged from 0.708 to 0.828 and 0.664 to 0.949 log CFU/g, respectively, depending on the microorganism and chicken liver samples. Overall, the results highlighted the ability of Salmonella not only to survive but also to grow at refrigeration temperatures and demonstrated the significant potential of FTIR technology in tandem with the proposed spectral analysis workflow for the estimation of total viable count, Pseudomonas spp., B. thermosphacta, LAB, Enterobacteriaceae, and Salmonella on chicken liver.

The Use of Less Conventional Meats or Meat with High pH Can Lead to the Growth of Undesirable Microorganisms during Natural Meat Fermentation

The bacterial communities that are established during natural meat fermentation depend on the processing conditions and the type of meat substrate used. Six pork samples of variable quality (reflected in pH values) and six less conventional meats (beef, horse, hare, wild deer, wild duck, and wild boar) were naturally fermented under controlled conditions in model systems. The development of lactic acid bacteria (LAB), coagulase-negative staphylococci (CNS), and enterobacteria was followed using culture-dependent techniques and (GTG)₅-PCR fingerprinting of genomic DNA from the isolates obtained. Taken together, Latilactobacillus sakei was the most abundant LAB species, although Latilactobacillus curvatus was more manifest in high-pH pork. Within staphylococci, common species were encountered (i.e., Staphylococcus equorum, Staphylococcus saprophyticus, and Staphylococcus xylosus), although some atypical ones (i.e., Staphylococcus succinus) were also recovered. Within enterobacteria, Serratia spp. prevailed in more acidic pork batches and in beef, whereas Hafnia spp. prevailed in game meat fermentations. Enterobacterial counts were particularly high in fermentations with low acidity, namely for some pork batches, hare, wild duck, and wild boar. These findings should be considered when naturally fermented meat products are manufactured, as the use of game meat or meat with high pH can give rise to safety concerns.