Meta-analysis of citrus-derived additives on chicken meat quality and safety: a comprehensive evaluation of acceptability, physicochemical properties, and microbial contamination

Citrus represents a valuable repository of antioxidant substances that possess the potential for the preservation of meat quality. This meta-analysis aimed to comprehensively assess the impact of citrus additives on the quality and safety of chicken meat. Adhering to the PRISMA protocol, we initially identified 103 relevant studies, from which 20 articles meeting specific criteria were selected for database construction. Through the amalgamation of diverse individual studies, this research provides a comprehensive overview of chicken meat quality and safety, with a specific focus on the influence of citrus-derived additives. Minimal alterations were observed in the nutritional quality of chicken meat concerning storage temperature and duration. The findings demonstrated a significant reduction in aerobic bacterial levels, with Citrus aurantiifolia exhibiting the highest efficacy (P < 0.01). Both extracted and nonextracted citrus components, applied through coating, curing, and marinating, effectively mitigated bacterial contamination. Notably, thiobarbituric acid reactive substances (TBARS) concentrations were significantly reduced, particularly with Citrus hystrix (P < 0.01). Total volatile base nitrogen (TVBN), an indicator of protein degradation, exhibited a decrease, with citrus extract displaying enhanced efficacy (P < 0.01). Chemical composition changes were marginal, except for a protein increase after storage (P < 0.01). Hedonic testing revealed varied preferences, indicating improvements in flavor, juiciness, and overall acceptability after storage (P < 0.01). The study underscores the effectiveness of citrus additives in preserving chicken meat quality, highlighting their antibacterial and antioxidant properties, despite some observed alterations in texture and chemical composition. Citrus additives have been proven successful in 1) mitigating adverse effects on chicken meat during storage, especially with Citrus hystrix exhibiting potent antimicrobial properties, and 2) enhancing the hedonic quality of chicken meat. This research strongly advocates for the application of citrus additives to uphold the quality and safety of chicken meat.

The regulation of carbon dioxide on food microorganisms: A review

This review presents a survey of two extremely important technologies about CO2 with the effectiveness of controlling microorganisms - atmospheric pressure CO2-based modified atmosphere packaging (MAP) and high pressure CO2 non-thermal pasteurization (HPCD). CO2-based MAP is effectively in delaying the lag and logarithmic phases of microorganisms by replacing the surrounding air, while HPCD achieved sterilization by subjecting food to either subcritical or supercritical CO2 for some time in a continuous, batch or semi-batch way. In addition to the advantages of healthy, eco-friendly, quality-preserving, effective characteristic, some challenges such as the high drip loss and packaging collapse associated with higher concentration of CO2, the fuzzy mechanisms of oxidative stress, the unproven specific metabolic pathways and biomarkers, etc., in CO2-based MAP, and the unavoidable extraction of bioactive compounds, the challenging application in solid foods with higher efficiency, the difficult balance between optimal sterilization and optimal food quality, etc., in HPCD still need more efforts to overcome. The action mechanism of CO2 on microorganisms, researches in recent years, problems and future perspectives are summarized. When dissolved in solution medium or cellular fluids, CO2 can form carbonic acid (H2CO3), and H2CO3 can further dissociate into bicarbonate ions (HCO3-), carbonate (CO32-) and hydrogen cations (H+) ionic species following series equilibria. The action mode of CO2 on microorganisms may be relevant to changes in intracellular pH, alteration of proteins, enzyme structure and function, alteration of cell membrane function and fluidity, and so on. Nevertheless, the effects of CO2 on microbial biofilms, energy metabolism, protein and gene expression also need to be explored more extensively and deeply to further understand the action mechanism of CO2 on microorganisms.

A culture-based assessment of the microbiota of conventional and free-range chicken meat from Irish processing facilities

Chicken meat is the most popularly consumed meat worldwide, with free-range and ethically produced meat a growing market among consumers. However, poultry is frequently contaminated with spoilage microbes and zoonotic pathogens which impact the shelf-life and safety of the raw product, constituting a health risk to consumers. The free-range broiler microbiota is subject to various influences during rearing such as direct exposure to the external environment and wildlife which are not experienced during conventional rearing practices. Using culture-based microbiology approaches, this study aimed to determine whether there is a detectable difference in the microbiota from conventional and free-range broilers from selected Irish processing plants. This was done through analysis of the microbiological status of bone-in chicken thighs over the duration of the meat shelf-life. It was found that the shelf-life of these products was 10 days from arrival in the laboratory, with no statistically significant difference (P > 0.05) evident between free-range and conventionally raised chicken meat. A significant difference, however, was established in the presence of pathogenesis-associated genera in different meat processors. These results reinforce past findings which indicate that the processing environment and storage during shelf-life are key determinants of the microflora of chicken products reaching the consumer.

Effect of CO2 on the spoilage potential of Shewanella putrefaciens target to flavour compounds

To investigate the regulation mechanism of CO₂ (0% CO₂, 20% CO₂, 60% CO₂, and 100% CO₂) on the spoilage potential of S. putrefaciens target to flavour compounds, the metabolic activity of S. putrefaciens and the changes in flavour compounds extracted from inoculated large yellow croakers were evaluated. Results showed that CO₂ significantly reduced biofilm formation capacity and suppressed synthesis of intracellular adenosine triphosphate (ATP). The production of unpleasant flavour compounds, such as total volatile basic nitrogen (TVB-N), trimethylamine (TMA), inosine (HxR), hypoxanthine (Hx), histidine, lysine, histamine, putrescine, 1-octen-3-ol, hexanal and benzaldehyde, was inhibited by CO₂. The hydrolysis and oxidation of lipid in CO₂-treated samples were alleviated and unsaturated fatty acids (UFAs) were in a higher percentage. In summary, CO₂ efficiently reduced the spoilage potential of S. putrefaciens and contributed to better flavour quality of samples during 4 °C storage. A more effective inhibition by 100% CO₂ was observed.

Identification, Characterization, and Antioxidant Potential of Bifidobacterium longum subsp. longum Strains Isolated From Feces of Healthy Infants

Increasing evidence has indicated that oxidative stress is associated with the health of infants. Bifidobacterium, especially B. longum subsp. longum strains, are abundant in the gut microbiota of infants, which may have the potential to ameliorate oxidative damage. Thus, this study aimed to isolate and screen B. longum subsp. longum strains with probiotic characters and antioxidant properties as infants’ dietary supplements. In this study, 24 B. longum subsp. longum strains were isolated from 15 healthy infants identified via 16S rRNA and heat shock protein 60 (hsp60) sequences. B. longum subsp. longum B13, F2, K4, K5, K10, K13, and K15 strains were selected based on high values obtained from autoaggregation, hydrophobicity, and adhesion assays to HT-29 cells. Among these seven strains, B. longum subsp. longum F2, K5, K10, and K15 were selected according to the high tolerance of gastrointestinal tract conditions compared to Bifidobacterium animalis subsp. lactis BB-12. Among these four strains, B. longum subsp. longum K5 was susceptible to common antibiotics and showed the highest intestinal epithelial cell proliferation of CCD 841 CoN. Additionally, B. longum subsp. longum K5 showed a strong antioxidant capacity, and its supernatant exhibited better activity of reducing power, hydroxyl radical scavenging, and DPPH radical scavenging than that of the intact cells with cell-free extracts. The findings indicated that B. longum subsp. longum K5 could be used as a probiotic candidate in infant nutrition.

Comparative Proteomics Reveals the Anaerobic Lifestyle of Meat-Spoiling Pseudomonas Species

The ability of certain Pseudomonas (P.) species to grow or persist in anoxic habitats by either denitrification, acetate fermentation, or arginine fermentation has been described in several studies as a special property. Previously, we had isolated strains belonging to the species P. lundensis, P. weihenstephanensis, and P. fragi from anoxic modified atmosphere packaged (MAP) minced beef and further proved their anaerobic growth in vitro on agar plates. This follow-up study investigated the anaerobic growth of two strains per respective species in situ on inoculated chicken breast filet under 100% N₂ modified atmosphere. We were able to prove anaerobic growth of all six strains on chicken breast filet with cell division rates of 0.2–0.8/day. Furthermore, we characterized the anaerobic metabolic lifestyle of these Pseudomonas strains by comparative proteomics, upon their cultivation in meat simulation media, which were constantly gassed with either air or 100% N₂ atmospheres. From these proteomic predictions, and respective complementation by physiological experiments, we conclude that the Pseudomonas strains P. fragi, P. weihenstephanensis, P. lundensis exhibit a similar anaerobic lifestyle and employ arginine fermentation via the arginine deiminase (ADI) pathway to grow anaerobically also on MAP meats. Furthermore, glucose fermentation to ethanol via the ED-pathway is predicted to enable long term survival but no true growth, while respiratory growth with nitrate as alternative electron acceptor or glucose fermentation to acetate could be excluded due to absence of essential genes. The citric acid cycle is partially bypassed by the glyoxylate shunt, functioning as the gluconeogenetic route without production of NADH₂ under carbon limiting conditions as e.g., in packaged meats. Triggered by an altered redox balance, we also detected upregulation of enzymes involved in protein folding as well as disulfide bonds isomerization under anoxic conditions as a counteracting mechanism to reduce protein misfolding. Hence, this study reveals the mechanisms enabling anaerobic grow and persistence of common meat-spoiling Pseudomonas species, and further complements the hitherto limited knowledge of the anaerobic lifestyle of Pseudomonas species in general.

Metagenomic analysis exploring taxonomic and functional diversity of bacterial communities of a Himalayan urban fresh water lake

Freshwater lakes present an ecological border between humans and a variety of host organisms. The present study was designed to evaluate the microbiota composition and distribution in Dal Lake at Srinagar, India. The non-chimeric sequence reads were classified taxonomically into 49 phyla, 114 classes, 185 orders, 244 families and 384 genera. Proteobacteria was found to be the most abundant bacterial phylum in all the four samples. The highest number of observed species was found to be 3097 in sample taken from least populated area during summer (LPS) whereas the summer sample from highly populated area (HPS) was found most diverse among all as indicated by taxonomic diversity analysis. The QIIME output files were used for PICRUSt analysis to assign functional attributes. The samples exhibited a significant difference in their microbial community composition and structure. Comparative analysis of functional pathways indicated that the anthropogenic activities in populated areas and higher summer temperature, both decrease functional potential of the Lake microbiota. This is probably the first study to demonstrate the comparative taxonomic diversity and functional composition of an urban freshwater lake amid its highly populated and least populated areas during two extreme seasons (winter and summer).

Characterization of the biofilm matrix composition of psychrotrophic, meat spoilage pseudomonads

Psychrotrophic Pseudomonas species are the key spoilage bacteria of aerobically stored chilled meat. These organisms readily form biofilms on meat under refrigerated conditions leading to consumer rejection and associated economic losses. Limited information is available on the matrix composition of the biofilms formed by these bacteria. We quantified and characterized the main components of the matrix of mono-species biofilms of selected Pseudomonas fragi and Pseudomonas lundensis strains using chemical analysis and Raman spectroscopy. The biofilms were grown at 10 °C and 25 °C on nitro-cellulose membranes placed on surface sterilized beef cuts. Extra-cellular polymeric substances of the matrix were extracted in soluble and bound forms and were chemically assessed for total carbohydrates, proteins and extra-cellular DNA. Both Pseudomonas species showed a significant increase in total carbohydrates and total proteins when grown at 10 °C as compared to 25 °C. Extra-cellular DNA did not show a strong correlation with growth temperature. Raman spectra were obtained from planktonic bacteria and membrane grown biofilms at 10 °C and 25 °C. Higher levels of guanine were detected in planktonic cells as compared to biofilm cells. This study suggests that psychrotrophic Pseudomonas species may respond to cold stress by increasing extra-cellular polymer secretions.

Lactic Acid Bacteria Adjunct Cultures Exert a Mitigation Effect against Spoilage Microbiota in Fresh Cheese

Lactic acid bacteria (LAB) have a strong mitigation potential as adjunct cultures to inhibit undesirable bacteria in fermented foods. In fresh cheese with low salt concentration, spoilage and pathogenic bacteria can affect the shelf life with smear on the surface and packaging blowing. In this work, we studied the spoilage microbiota of an Italian fresh cheese to find tailor-made protective cultures for its shelf life improvement. On 14-tested LAB, three of them, namely Lacticaseibacillus rhamnosus LRH05, Latilactobacillus sakei LSK04, and Carnobacterium maltaromaticum CNB06 were the most effective in inhibiting Gram-negative bacteria. These cultures were assessed by the cultivation-dependent and DNA metabarcoding approach using in vitro experiments and industrial trials. Soft cheese with and without adjunct cultures were prepared and stored at 8 and 14 °C until the end of the shelf life in modified atmosphere packaging. Data demonstrated that the use of adjunct cultures reduce and/or modulate the growth of spoilage microbiota at both temperatures. Particularly, during industrial experiments, C. maltaromaticum CNB06 and Lcb. rhamnosus RH05 lowered psychrotrophic bacteria of almost 3 Log CFU/g in a 5-week stored cheese. On the contrary, Llb. sakei LSK04 was able to colonize the cheese but it was not a good candidate for its inhibition capacity. The combined approach applied in this work allowed to evaluate the protective potential of LAB strains against Gram-negative communities.

Dynamic changes of the bacterial communities in roast chicken stored under normal and modified atmosphere packaging

This study systematically investigated the dynamic changes in bacterial communities in roast chicken in normal and modified atmosphere packaging (MAP). The samples were stored under normal atmosphere and 40%/60% CO₂ /N₂ MAP conditions for 28 days at 4 °C. Changes in the number and type of microorganisms in roast chicken during storage were defined via cultural and 16S rDNA sequencing techniques. More Bacteroides, Chryseobacterium, Lactobacillus, and Acinetobacter than other bacteria were initially found in roast chicken. With normal packaging, Pseudomonas rapidly multiplied and became the main spoilage organism in roast chicken after 7 days, with a relative abundance of >90% of the entire bacterial flora. With MAP, due to the high salt content, Halomonas became the main spoilage organism in roast chicken by the middle of the storage period (14 days). Between days 21 and 28 of storage, Pseudomonas gradually became the main spoilage organism in roast chicken, but its relative abundance was much lower in MAP than in normal packaging, followed by Lachnospiraceae (NK4A136 group) and Altererythrobacter. Our research shows that the microbes in roast chicken mainly originated from the processing environment and operators. The combination of MAP with a low storage temperature could effectively improve the quality and safety of roast chicken meat. PRACTICAL APPLICATIONS: This research showed the dynamic changes in the bacterial community of roast chicken stored under normal and modified atmosphere packaging (MAP). Microorganisms in roast chicken are mainly obtained from the processing environment and operators. Combining MAP with storage at low temperatures can effectively improve the quality and safety of roast chicken.

Isolation, identification and biodiversity of antiscalant degrading seawater bacteria using MALDI-TOF-MS and multivariate analysis

Seawater reverse osmosis (SWRO) is a commonly used desalination technique owing to its lesser environmental and economic impacts as compared to thermal desalination techniques. Antiscalants are used in SWRO to reduce membrane scaling caused by the supersaturation of salts present in feed water. However, to remain effective in reducing membrane scaling, antiscalants should be highly stable and resistant to biological degradation by seawater microorganisms. In this research, several bacteria from Qatar's seawater were isolated and screened for their ability to use antiscalants as a carbon and energy source. The biodiversity of antiscalant degrading seawater bacteria was demonstrated through combining the techniques of MALDI-TOF MS and principle component analysis. It was found that the bacteria isolated from Qatar's seawater such as H. aquamarina, H. elongata, P. fragi, P. stutzeri and others can degrade antiscalants and use them as a carbon and energy source. It was observed that the growth rates varied based on the type of antiscalant and the bacteria used. Among the tested strains, H. aquamarina, which is also known for its potential to cause biofouling, demonstrated the highest growth rates in antiscalants media. Thus, it was concluded that there is wide variety of bacteria in Qatar's seawater that can biodegrade the antiscalants; reducing their efficiency to combat membrane scaling. Since, these antiscalants will be used as a source of carbon and energy, microbial growth will increase resulting in enhanced membrane biofouling in SWRO.

Modified atmosphere packaging decreased Pseudomonas fragi cell metabolism and extracellular proteolytic activities on meat

Modified atmosphere packaging (MAP) is considered an effective method for extending the shelf life of meat. The use of optimal mixture of gases (CO₂ and N₂) in food packaging containers has been proved to effectively inhibit the growth of microorganisms in poultry meat. In general, a minimum CO₂ concentration range of 20%-30% is required for the inhibitory effect. The aim of this study was to investigate the mechanism by which MAP (CO₂/N₂ 30%/70%) inhibits Pseudomonas fragi, a dominant spoilage microorganism in aerobically stored chilled meat. The cell physiological changes were determined by measuring membrane integrity, membrane potential, ATP level, and extracellular proteolytic activity. The results showed that samples stored under MA retained cell membrane integrity, but lost significant membrane potential and ATP synthesis activity. Furthermore, the peptides issued from 2 structural proteins (myosin and actin) were mainly identified in air samples, indicating that these fragments result from bacterial proteolytic activity while MAP inhibited this activity. Overall, the study found that cell metabolism and extracellular protease activity decreased under MAP conditions. This study showed that MAP is an effective food preservation strategy and revealed mechanisms by which MAP inhibits spoilage.

Transcriptome Analysis of the Global Response of Pseudomonas fragi NMC25 to Modified Atmosphere Packaging Stress

Pseudomonas fragi is usually isolated from chilled meats in relation to their spoilage, while many studies have shown that the application of modified atmosphere packaging (MAP) inhibits the spoilage potential of P. fragi. The effects of MAP on P. fragi NMC25 metabolism were determined in the present study by exposing this organism to different air conditions and comparing the resulting transcriptome profiles. We found 559 differentially expressed genes by RNA-seq, and the results revealed that MAP decreases the expression of genes involved in the electron transport chain (nuoAB), resulting in an inhibition of aerobic respiration. Meanwhile, MAP also induced the downregulation of genes responsible for ATP-binding cassette transporters, flagellar and type I fimbrial proteins, and DNA replication and repair, which may further influence nutrient uptake, motility, and growth. In addition, NMC25 cells modified their pathways for energy production, amino acid synthesis, membrane lipid composition, and other metabolic patterns to adapt to MAP. These data show that P. fragi NMC25 survives under MAP but reduces part of its metabolism related to its spoilage ability.