Natural Polyphenols for the Preservation of Meat and Dairy Products

Food spoilage makes foods undesirable and unacceptable for human use. The preservation of food is essential for human survival, and different techniques were initially used to limit the growth of spoiling microbes, e.g., drying, heating, salting, or fermentation. Water activity, temperature, redox potential, preservatives, and competitive microorganisms are the most important approaches used in the preservation of food products. Preservative agents are generally classified into antimicrobial, antioxidant, and anti-browning agents. On the other hand, artificial preservatives (sorbate, sulfite, or nitrite) may cause serious health hazards such as hypersensitivity, asthma, neurological damage, hyperactivity, and cancer. Thus, consumers prefer natural food preservatives to synthetic ones, as they are considered safer. Polyphenols have potential uses as biopreservatives in the food industry, because their antimicrobial and antioxidant activities can increase the storage life of food products. The antioxidant capacity of polyphenols is mainly due to the inhibition of free radical formation. Moreover, the antimicrobial activity of plants and herbs is mainly attributed to the presence of phenolic compounds. Thus, incorporation of botanical extracts rich in polyphenols in perishable foods can be considered since no pure polyphenolic compounds are authorized as food preservatives. However, individual polyphenols can be screened in this regard. In conclusion, this review highlights the use of phenolic compounds or botanical extracts rich in polyphenols as preservative agents with special reference to meat and dairy products.

Near-Infrared Fluorescent Probe with a Large Stokes Shift for Detection of Hydrogen Sulfide in Food Spoilage, Living Cells, and Zebrafish

Hydrogen sulfide (H₂S) is a significant component of various physiological processes, and it can also cause a negative effect on foodstuffs. In this work, we designed and synthesized an NIR fluorescent turn-on responding probe (DDM-H₂S) with a large Stokes shift (190 nm) for the detection of H₂S. DDM-H₂S exhibited high selectivity and sensitivity, obvious color changes, and a fast response time for tracing H₂S. When DDM-H₂S reacted with H₂S, the PET process was eliminated, and the recovered ICT process and NIR fluorescence were observed. Moreover, DDM-H₂S could image endogenous and exogenous H₂S in living HeLa cells and zebrafish. What is more, the probe DDM-H₂S could be deposited easily to test paper strips, which were able to detect the H₂S gas produced during food spoilage (such as eggs, raw meat, and fishes) by the color of test paper strips changing from pink to purple. Therefore, this work provides a promising approach for monitoring H₂S in complicated biological systems and practical food samples.

The control of fungi and mycotoxins by food active packaging: a review

Conventionally used petrochemical-based plastics are poorly degradable and cause severe environmental pollution. Alternatively, biopolymers (e.g., polysaccharides, proteins, lipids, and their blends) are biodegradable and environment-friendly, and thus their use in packaging technologies has been on the rise. Spoilage of food by mycotoxigenic fungi poses a severe threat to human and animal health. Hence, because of the adverse effects of synthetic preservatives, active packaging as an effective technique for controlling and decontaminating fungi and related mycotoxins has attracted considerable interest. The current review aims to provide an overview of the prevention of fungi and mycotoxins through active packaging. The impact of different additives on the antifungal and anti-mycotoxigenic functionality of packaging incorporating active films/coatings is also investigated. In addition, active packaging applications to control and decontaminate common fungi and mycotoxins in bakery products, cereal grains, fruits, nuts, and dairy products are also introduced. The results of recent studies have confirmed that biopolymer films and coatings incorporating antimicrobial agents provide great potential for controlling common fungi and mycotoxins and enhancing food quality and safety.

Antifungal Metabolites as Food Bio-Preservative: Innovation, Outlook, and Challenges

Perishable food spoilage caused by fungi is a major cause of discomfort for food producers. Food sensory abnormalities range from aesthetic degeneration to significant aroma, color, or consistency alterations due to this spoilage. Bio-preservation is the use of natural or controlled bacteria or antimicrobials to enhance the quality and safety of food. It has the ability to harmonize and rationalize the required safety requirements with conventional preservation methods and food production safety and quality demands. Even though synthetic preservatives could fix such issues, there is indeed a significant social need for "clean label" foods. As a result, consumers are now seeking foods that are healthier, less processed, and safer. The implementation of antifungal compounds has gotten a lot of attention in recent decades. As a result, the identification and characterization of such antifungal agents has made promising advances. The present state of information on antifungal molecules, their modes of activity, connections with specific target fungi varieties, and uses in food production systems are summarized in this review.

In Vitro Evaluation of Biological Activities and Phytochemical Analysis of Different Solvent Extracts of Punica granatum L. (Pomegranate) Peels

Antimicrobial resistance is a public health concern resulting in high rates of morbidity and mortality worldwide. Furthermore, a high incidence of food poisoning diseases besides harmful implications of applying synthetic food additives in food preservation necessitates fabrication of safe food preservatives. Additionally, damaging effects of free radicals on human health has been reported to be involved in the incidence of serious diseases, including cancer, diabetes and cardiovascular diseases; hence, finding safe sources of antioxidants is vital. Therefore, the present study was carried out to assess the antibacterial, antiradical and carcinopreventive efficacy of different solvent extracts of pomegranate peels. Agar disk diffusion assay revealed that Staphylococcus aureus, MRSA, E. coli and S. typhimurium were highly susceptible to methanolic fraction of Punica granatum L. peels recording inhibition zones of 23.7, 21.8, 15.6 and 14.7 mm respectively. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the methanolic fraction of Punica granatum L. peels against S. aureus were 0.125 and 0.250 mg/mL, respectively. In addition, the pomegranate acetonic and methanolic fractions revealed an impressive antiradical efficiency against DPPH (2,2-diphenyl-1-picrylhydrazyl) radical recording radical scavenging activity percentages of 86.9 and 79.4%, respectively. In this regard, the acetonic fraction of pomegranate peels revealed the highest anti-proliferative efficiency after 48 h incubation against MCF7 cancer cells recording IC₅₀ of 8.15 µg/mL, while the methanolic extract was highly selective against transformed cancer cells compared to normal cell line recording selectivity index of 5.93. GC-MS results demonstrated that 5-Hydroxymethylfurfural was the main active component of methanolic and acetonic extracts of pomegranate peels recording relative percentages of 37.55 and 28.84% respectively. The study recommends application of pomegranate peel extracts in the biofabrication of safe food preservatives, antioxidants and carcinopreventive agents.

Development and validation of a one-step modelling approach for the determination of chicken meat shelf-life based on the growth kinetics of Pseudomonas spp

The main objective of the present study was to investigate the effect of storage temperature on aerobically stored chicken meat spoilage using the two-step and one-step modelling approaches involving different primary models namely the modified Gompertz, logistic, Baranyi and Huang models. For this purpose, growth data points of Pseudomonas spp. were collected from published studies conducted in aerobically stored chicken meat product. Temperature-dependent kinetic parameters (maximum specific growth rate 'µ_max' and lag phase duration 'λ') were described as a function of storage temperature through the Ratkowsky model based on the different primary models. Then, the fitting capability of both modelling approaches was compared taking into account root mean square error, adjusted coefficient of determination (adjusted-R²) and corrected Akaike information criterion. The one-step modelling approach showed considerably improved fitting capability regardless of the used primary model. Finally, models developed from the one-step modelling approach were validated for the maximum growth rate data extracted from independent published literature using the statistical indexes Bias (B_f) and Accuracy (A_f) factors. The best prediction capability was obtained for the Baranyi model with B_f and A_f being very close to 1. The shelf-life of chicken meat as a function of storage temperature was predicted using both modelling approaches for the Baranyi model.

Essential Oils from Fruit and Vegetables, Aromatic Herbs, and Spices: Composition, Antioxidant, and Antimicrobial Activities

In the field of food preservation, encapsulated Essential Oils (EOs) could be the best non-toxic and eco-friendly tool for food preservative applications substituting the chemicals ones that have several disadvantages for the environment and health. Thirteen commercial EOs from plants, fruits, and vegetables were characterized by GC-MS. The antioxidant activity was measured by DPPH and ABTS techniques. Antimicrobial activity was assessed by agar well-diffusion method and the Minimum Inhibitory Concentration (MIC) by agar dilution method against six bacteria, Candida albicans, and Botrytis cinerea. All the EOs tested have demonstrated antioxidant activity in the range of IC50 0.01-105.32 mg/mL. Between them, cinnamon EOs were the best, followed by oregano and thyme EOs. Fennel EO showed the lowest radical scavenging. MIC values ranged from 0.14 to 9 mg/mL. C. cassia, thyme, and oregano EOs were the most effective against the bacterial species tested, and the yeast C. albicans. On the contrary, citric fruit EOs showed low or no inhibition against most bacterial strains. The percentages of inhibition of mycelia growth of B. cinerea ranged from 3.4 to 98.5%. Thyme, oregano, mint, and fennel EOs showed the highest inhibition.

Awareness, Experience, and Knowledge of Farming Households in Rural Bangladesh Regarding Mold Contamination of Food Crops: A Cross-Sectional Study

Aside from specific environmental conditions, poor agricultural practices contribute to mold and thus the mycotoxin contamination of crops. This study investigated Bangladeshi farming households' (i) awareness of and experience with mold contamination of food crops; (ii) knowledge and awareness of the timing, causes, and consequences of mold and mycotoxin contamination; and (iii) knowledge of the recommended agricultural practices for controlling and preventing mold contamination of food crops. A survey was conducted with 1280 households in rural areas of Habiganj district, Bangladesh. Basic descriptive statistics were calculated, and mixed-effects linear regression analyses were performed to examine associations between household characteristics and overall knowledge scores. The awareness of mold contamination of food crops was very high (99%; 95% CI: 98-100%) and a shared experience among households (85%; 95% CI: 80-88%). Yet, the majority (80%; 95% CI: 76-84%) demonstrated a low level of knowledge of the timing, causes, and preventive practices regarding mold contamination of crops. Knowledge scores were similar over demographic groups and better for households with more arable land. The findings suggest a generally insufficient knowledge of the conditions that favor mold contamination and the measures for preventing mold contamination of food crops. These findings underline the need for tailored interventions to promote good agricultural practices and reduce mold contamination of food crops.

Bioactive Electrospun Fibers of Poly(ε-Caprolactone) Incorporating α-Tocopherol for Food Packaging Applications

Antioxidant activity is an important feature for food contact materials such as packaging, aiming to preserve freshness and retard food spoilage. Common bioactive agents are highly susceptible to various forms of degradation; therefore, protection is required to maintain functionality and bioavailability. Poly(ε-caprolactone) (PCL), a biodegradable GRAS labeled polymer, was used in this study for encapsulation of α-tocopherol antioxidant, a major component of vitamin E, in the form of electrospun fibers. Rheological properties of the fiber forming solutions, which determine the electrospinning behavior, were correlated with the properties of electrospun fibers, e.g., morphology and surface properties. Interactions through hydrogen bonds were evidenced between the two components. These have strong effect on structuration of macromolecular chains, especially at low α-tocopherol amounts, decreasing viscosity and elastic modulus. Intra-molecular interactions in PCL strengthen at high α-tocopherol amounts due to decreased solvation, allowing good structural recovery after cease of mechanical stress. Morphologically homogeneous electrospun fibers were obtained, with ~6 μm average diameter. The obtained fibers were highly hydrophobic, with fast release in 95% ethanol as alternative simulant for fatty foods. This induced good in vitro antioxidant activity and significant in vivo reduction of microbial growth on cheese, as determined by respirometry. Therefore, the electrospun fibers from PCL entrapping α-tocopherol as bioactive agent showed potential use in food packaging materials.

Sphingomonas aliaeris sp. nov., a new species isolated from pork steak packed under modified atmosphere

Species belonging to the genus Sphingomonas have been isolated from environments such as soil, water and plant tissues. Many strains are known for their capability of degrading aromatic molecules and producing extracellular polymers. A Gram-stain-negative, strictly aerobic, motile, red-pigmented, oxidase-negative, catalase-positive, rod-shaped strain, designated DH-S5^T, has been isolated from pork steak packed under CO₂-enriched modified atmosphere. Cell diameters were 1.5×0.9 µm. Growth optima were at 30 °C and at pH 6.0. Phylogenetic analyses based on both complete 16S rRNA gene sequence and whole-genome sequence data revealed that strain DH-S5^T belongs to the genus Sphingomonas, being closely related to Sphingomonas alpina DSM 22537^T (97.4 % gene sequence similarity), followed by Sphingomonas qilianensis X1^T (97.4 %) and Sphingomonas hylomeconis GZJT-2^T (97.3 %). The DNA G+C content was 64.4 mol%. The digital DNA-DNA hybridization value between the isolate strain and S. alpina DSM 22537^T was 21.0 % with an average nucleotide identity value of 77.03 %. Strain DH-S5^T contained Q-10 as the ubiquinone and major fatty acids were C_18 : 1 cis 11 (39.3 %) and C_16 : 1 cis 9 (12.5 %), as well as C_16 : 0 (12.1 %) and C_14 : 0 2-OH (11.4 %). As for polar lipids, phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, dimethylphosphatidylethanolamine and sphingoglycolipid could be detected, alongside traces of monomethylphosphatidylethanolamine. Based on its phenotypic, chemotaxonomic and phylogenetic characteristics, strain DH-S5^T (=DSM 110829^T=LMG 31606^T) is classified as a representative of the genus Sphingomonas, for which the name Sphingomonas aliaeris sp. nov. is proposed.

Towards a Bioactive Food Packaging: Poly(Lactic Acid) Surface Functionalized by Chitosan Coating Embedding Clove and Argan Oils

Here we introduce a new method aiming the immobilization of bioactive principles onto polymeric substrates, combining a surface activation and emulsion entrapment approach. Natural products with antimicrobial/antioxidant properties (essential oil from Syzygium aromaticum-clove and vegetal oil from Argania spinosa L-argan) were stabilized in emulsions with chitosan, a natural biodegradable polymer that has antimicrobial activity. The emulsions were laid on poly(lactic acid) (PLA), a synthetic biodegradable plastic from renewable resources, which was previously activated by plasma treatment. Bioactive materials were obtained, with low permeability for oxygen, high radical scavenging activity and strong inhibition of growth for Listeria monocytogenes, Salmonella Typhimurium and Escherichia coli bacteria. Clove oil was better dispersed in a more stable emulsion (no separation after six months) compared with argan oil. This leads to a compact and finely structured coating, with better overall properties. While both clove and argan oils are highly hydrophobic, the coatings showed increased hydrophilicity, especially for argan, due to preferential interactions with different functional groups in chitosan. The PLA films coated with oil-loaded chitosan showed promising results in retarding the food spoilage of meat, and especially cheese. Argan, and in particular, clove oil offered good UV protection, suitable for sterilization purposes. Therefore, using the emulsion stabilization of bioactive principles and immobilization onto plasma activated polymeric surfaces we obtained a bioactive material that combines the physical properties and the biodegradability of PLA with the antibacterial activity of chitosan and the antioxidant function of vegetal oils. This prevents microbial growth and food oxidation and could open new perspectives in the field of food packaging materials.

Metal Cation Triggered Peptide Hydrogels and Their Application in Food Freshness Monitoring and Dye Adsorption

Metal-ligand interactions have emerged as an important tool to trigger and modulate self-assembly, and to tune the properties of the final supramolecular materials. Herein, we report the metal-cation induced self-assembly of a pyrene-peptide conjugate to form hydrogels. The peptide has been rationally designed to favor the formation of β-sheet 1D assemblies and metal coordination through the Glu side chains. We studied in detail the self-assembly process in the presence of H+, Li+, Na+, K+, Ca2+, Ni2+, Cu2+, Zn2+, Cd2+, Co2+, Fe3+, and Cr3+ and found that the morphology and mechanical properties of the hydrogels are ion-dependent. Moreover, thanks to the presence of the metal, new applications could be explored. Cu2+ metallogels could be used for amine sensing and meat freshness monitoring, while Zn2+ metallogels showed good selectivity for cationic dye adsorption and separation.

The Aspergillus niger Major Allergen (Asp n 3) DNA-Specific Sequence Is a Reliable Marker to Identify Early Fungal Contamination and Postharvest Damage in Mangifera indica Fruit

The aim of this work was to study the value of the main allergen Asp n 3 of Aspergillus niger as a molecular marker of allergenicity and pathogenicity with the potential to be used in the identification of A. niger as a contaminant and cause of spoilage of Mangifera indica. Real-time polymerase chain reaction (RT-PCR) was used for the amplification of Asp n 3 gene. Two pairs of primers were designed: one for the amplification of the entire sequence and another one for the amplification of the most conserved region of this peroxisomal protein. The presence of A. niger was demonstrated by the early detection of the allergenic protein Asp n 3 coding gene, which could be considered a species-specific marker. The use of primers designed based on the conserved region of the Asp n 3 encoding gene allowed us to identify the presence of the closely related fungal species Aspergillus fumigatus by detecting Asp n 3 homologous protein, which can be cross-reactive. The use of conserved segments of the Asp n 3 gene or its entire sequence allows us to detect phylogenetically closely related species within the Aspergilaceae family or to identify species-specific contaminating fungi.

Bacteriocins, A Natural Weapon Against Bacterial Contamination for Greater Safety and Preservation of Food: A Review

Nowadays, consumers have become increasingly attentive to human health and the use of more natural products. Consequently, the demand for natural preservatives in the food industry is more frequent. This has led to intense research to discover new antimicrobial compounds of natural origin that could effectively fight foodborne pathogens. This research aims to safeguard the health of consumers and, above all, to avoid potentially harmful chemical compounds. Lactobacillus is a bacterial genus belonging to the Lactic Acid Bacteria and many strains are defined GRAS, generally recognized as safe. These strains are able to produce substances with antibacterial activity against food spoilage bacteria and contaminating pathogens: the bacteriocins. The aim of this review was to focus on this genus and its capability to produce antibacterial peptides. The review collected all the information from the last few years about bacteriocins produced by Lactobacillus strains, isolated from clinical or food samples, with remarkable antimicrobial activities useful for being exploited in the food field. In addition, the advantages and disadvantages of their use and the possible ways of improvement for industrial applications were described.

Abundant Small Protein ICARUS Inside the Cell Wall of Stress-Resistant Ascospores of Talaromyces macrosporus Suggests a Novel Mechanism of Constitutive Dormancy

Ascospores of Talaromyces.macrosporus belong to the most stress resistant eukaryotic cells and show a constitutive dormancy, i.e., no germination occurs in the presence of rich growth medium. Only an extreme trigger as very high temperature or pressure is able to evoke synchronized germination. In this study, several changes within the thick cell wall of these cells are observed after a heat treatment: (i.) a change in its structure as shown with EPR and X-ray diffraction; (ii.) a release of an abundant protein into the supernatant, which is proportional to the extent of heat activation; (iii.) a change in the permeability of the cell wall as judged by fluorescence studies in which staining of the interior of the cell wall correlates with germination of individual ascospores. The gene encoding the protein, dubbed ICARUS, was studied in detail and was expressed under growth conditions that showed intense ascomata (fruit body) and ascospore formation. It encodes a small 7–14 kD protein. Blast search exhibits that different Talaromyces species show a similar sequence, indicating that the protein also occurs in other species of the genus. Deletion strains show delayed ascomata formation, release of pigments into the growth medium, higher permeability of the cell wall and a markedly shorter heat activation needed for activation. Further, wild type ascospores are more heat-resistant. All these observations suggest that the protein plays a role in dormancy and is related to the structure and permeability of the ascospore cell wall. However, more research on this topic is needed to study constitutive dormancy in other fungal species that form stress-resistant ascospores.

Biosensors for Biogenic Amines: A Review

Biogenic amines (BAs) are well-known biomolecules, mostly for their toxic and carcinogenic effects. Commonly, they are used as an indicator of quality preservation in food and beverages since their presence in higher concentrations is associated with poor quality. With respect to BA’s metabolic pathways, time plays a crucial factor in their formation. They are mainly formed by microbial decarboxylation of amino acids, which is closely related to food deterioration, therefore, making them unfit for human consumption. Pathogenic microorganisms grow in food without any noticeable change in odor, appearance, or taste, thus, they can reach toxic concentrations. The present review provides an overview of the most recent literature on BAs with special emphasis on food matrixes, including a description of the typical BA assay formats, along with its general structure, according to the biorecognition elements used (enzymes, nucleic acids, whole cells, and antibodies). The extensive and significant amount of research that has been done to the investigation of biorecognition elements, transducers, and their integration in biosensors, over the years has been reviewed.

Smart edible films based on mucilage of lallemantia iberica seed incorporated with curcumin for freshness monitoring

The objective of the present work was first to develop a smart packaging system based on Lallemantia iberica seed gum (LISG)/curcumin and, subsequently, investigate its physicochemical characteristics and biological activity. Finally, the response of LISG/curcumin films against pH change and the spoilage of shrimp were tested. The barrier properties and mechanical performance of the films improved as the curcumin concentration increased. FT-IR analysis revealed the formation of physical interaction between LISG and curcumin. LISG/curcumin films showed a continuous and steady release of curcumin. The incorporation of curcumin into LISG matrix imparts antioxidant and antibacterial/mold activity to the films. A strong positive correlation was observed between total volatile base nitrogen (TVBN) content of shrimp and a* (redness) during storage time (Pearson correlation = 0.975). Eventually, LISG/curcumin film could be a promising smart packaging system capable of detecting food spoilage.

Plant compounds for the potential reduction of food waste - a focus on antimicrobial peptides

A large portion of global food waste is caused by microbial spoilage. The modern approach to preserve food is to apply different hurdles for microbial pathogens to overcome. These vary from thermal processes and chemical additives, to the application of irradiation and modified atmosphere packaging. Even though such preservative techniques exist, loss of food to spoilage still prevails. Plant compounds and peptides represent an untapped source of potential novel natural food preservatives. Of these, antimicrobial peptides (AMPs) are very promising for exploitation. AMPs are a significant component of a plant's innate defense system. Numerous studies have demonstrated the potential application of these AMPs; however, more studies, particularly in the area of food preservation are warranted. This review examines the literature on the application of AMPs and other plant compounds for the purpose of reducing food losses and waste (including crop protection). A focus is placed on the plant defensins, their natural extraction and synthetic production, and their safety and application in food preservation. In addition, current challenges and impediments to their full exploitation are discussed.

Antimicrobial Activity of Lipopeptide Biosurfactants Against Foodborne Pathogen and Food Spoilage Microorganisms and Their Cytotoxicity

Lipopeptide biosurfactants produced by Bacillus sp. were assessed regarding their antimicrobial activity against foodborne pathogenic and food spoilage microorganisms. Both Gram-positive and Gram-negative bacteria were found not to be susceptible to these lipopeptides. However, mycosubtilin and mycosubtilin/surfactin mixtures were very active against the filamentous fungi Paecilomyces variotti and Byssochlamys fulva, with minimum inhibitory concentrations (MICs) of 1-16 mg/L. They were also active against Candida krusei, MIC = 16-64 mg/L. Moreover it was found that the antifungal activity of these lipopeptides was not affected by differences in isoform composition and/or purity. Furthermore their cytotoxicity tested on two different cell lines mimicking ingestion and detoxification was comparable to those of approved food preservatives such as nisin. Overall, for the first time here mycosubtilin and mycosubtilin/surfactin mixtures were found to have high antifungal activity against food relevant fungi at concentrations lower than their toxicity level hence, suggesting their application for extending the shelf-life of products susceptible to these moulds. In addition combining nisin with mycosubtilin or mycosubtiliin/surfactin mixtures proved to be an effective approach to produce antimicrobials with broader spectrum of action.

Longitudinal Metatranscriptomic Analysis of a Meat Spoilage Microbiome Detects Abundant Continued Fermentation and Environmental Stress Responses during Shelf Life and Beyond

Microbial food spoilage is a complex phenomenon associated with the succession of the specific spoilage organisms (SSO) over the course of time. We performed a longitudinal metatranscriptomic study on one modified-atmosphere-packaged (MAP) beef product to increase understanding of the longitudinal behavior of a spoilage microbiome during shelf life and beyond. Based on the annotation of the mRNA reads, we recognized three stages related to the active microbiome that were descriptive of the sensory quality of the beef: acceptable product (AP), early spoilage (ES), and late spoilage (LS). Both the 16S RNA taxonomic assignments from the total RNA and functional annotations of the active genes showed that these stages were significantly different from each other. However, the functional gene annotations showed more pronounced differences than the taxonomy assignments. Psychrotrophic lactic acid bacteria (LAB) formed the core of the SSO, according to the transcribed reads. Leuconostoc species were the most abundant active LAB throughout the study period, whereas the transcription activity of Streptococcaceae (mainly Lactococcus) increased after the product had spoiled. In the beginning of the experiment, the community managed environmental stress by cold-shock responses, which were followed by expression of the genes involved in managing oxidative stress. Glycolysis, the pentose phosphate pathway, and pyruvate metabolism were active throughout the study at a relatively stable level. However, the proportional transcription activities of the enzymes in these pathways changed over time.IMPORTANCE It is generally known which organisms are the typical SSO in foods, whereas the actively transcribed genes and pathways during microbial succession are poorly understood. This knowledge is important, since better approaches to food quality evaluation and shelf life determination are needed. Therefore, we conducted this study to find longitudinal markers that are connected to quality deterioration in a MAP beef product. This kind of RNA marker could be used to develop novel types of rapid quality analysis tools in the future. New tools are needed, since even though SSO can be detected and their concentrations determined using the current microbiological methods, results from these analyses cannot predict how close in time a spoilage community is to the production of clear sensory defects. The main reason for this is that the species composition of a spoilage community does not change dramatically during late shelf life, whereas the ongoing metabolic activities lead to the development of notable sensory deterioration.

Understanding How Microorganisms Respond to Acid pH Is Central to Their Control and Successful Exploitation

Microbes from the three domains of life, Bacteria, Archaea, and Eukarya, share the need to sense and respond to changes in the external and internal concentrations of protons. When the proton concentration is high, acidic conditions prevail and cells must respond appropriately to ensure that macromolecules and metabolic processes are sufficiently protected to sustain life. While, we have learned much in recent decades about the mechanisms that microbes use to cope with acid, including the unique challenges presented by organic acids, there is still much to be gained from developing a deeper understanding of the effects and responses to acid in microbes. In this perspective article, we survey the key molecular mechanisms known to be important for microbial survival during acid stress and discuss how this knowledge might be relevant to microbe-based applications and processes that are consequential for humans. We discuss the research approaches that have been taken to investigate the problem and highlight promising new avenues. We discuss the influence of acid on pathogens during the course of infections and highlight the potential of using organic acids in treatments for some types of infection. We explore the influence of acid stress on photosynthetic microbes, and on biotechnological and industrial processes, including those needed to produce organic acids. We highlight the importance of understanding acid stress in controlling spoilage and pathogenic microbes in the food chain. Finally, we invite colleagues with an interest in microbial responses to low pH to participate in the EU-funded COST Action network called EuroMicropH and contribute to a comprehensive database of literature on this topic that we are making publicly available.

Genetic Diversity, Ochratoxin A and Fumonisin Profiles of Strains of Aspergillus Section Nigri Isolated from Dried Vine Fruits

We investigated ochratoxin A (OTA) contamination in raisin samples purchased from Slovak markets and determined the diversity of black-spored aspergilli as potential OTA and fumonisin (FB1 and FB2) producers. The taxonomic identification was performed using sequences of the nuclear ITS1-5.8s-ITS2 region, the calmodulin and beta-tubulin genes. We obtained 239 isolates from eight fungal genera, of which 197 belonged to Aspergillus (82%) and 42 strains (18%) to other fungal genera. OTA contamination was evidenced in 75% of the samples and its level ranged from 0.8 to 10.6 µg/kg. The combination of all three markers used enabled unambiguous identification of A. carbonarius, A. luchuensis, A. niger, A. tubingensis and A. welwitschiae. The dominant coloniser, simultaneously having the highest within-species diversity isolated from our raisin samples, was A. tubingensis. Out of all analysed strains, only A. carbonarius was found to produce OTA, but in relatively high quantity (2477–4382 µg/kg). The production of FB1 and FB2 was evidenced in A. niger strains only.

Potential of N2 Gas Flushing to Hinder Dairy-Associated Biofilm Formation and Extension

Worldwide, the dairy sector remains of vital importance for food production despite severe environmental constraints. The production and handling conditions of milk, a rich medium, promote inevitably the entrance of microbial contaminants, with notable impact on the quality and safety of raw milk and dairy products. Moreover, the persistence of high concentrations of microorganisms (especially bacteria and bacterial spores) in biofilms (BFs) present on dairy equipment or environments constitutes an additional major source of milk contamination from pre- to post-processing stages: in dairies, BFs represent a major concern regarding the risks of disease outbreaks and are often associated with significant economic losses. One consumption trend toward "raw or low-processed foods" combined with current trends in food production systems, which tend to have more automation and longer processing runs with simultaneously more stringent microbiological requirements, necessitate the implementation of new and obligatory sustainable strategies to respond to new challenges regarding food safety. Here, in light of studies, performed mainly with raw milk, that considered dominant "planktonic" conditions, we reexamine the changes triggered by cold storage alone or combined with nitrogen gas (N2) flushing on bacterial populations and discuss how the observed benefits of the treatment could also contribute to limiting BF formation in dairies.

Comparative Proteome Analysis of Shewanella putrefaciens WS13 Mature Biofilm Under Cold Stress

Worldwide, Shewanella putrefaciens is the predominant seafood spoilage microorganism during cold storage. This bacterium can attach to biotic/abiotic surfaces to form biofilms which contribute to seafood quality degradation and shelf-life reduction. The mechanism of S. putrefaciens biofilm formation is not yet described. Crystal violet staining in combination with confocal laser scanning microscopy (CLSM) was used to study the sequence of events leading to the establishment of a mature biofilm at 4, 15, and 30°C. In addition, the main chemical constituents of the mature biofilm were determined by Raman spectroscopy (RM), whereas, comparative proteomic analysis was used to quantify changes in metabolic pathways and to find out underlying protein determinants. The physical dimensions of the mature biofilm, i.e., biomass, biovolume, and mean thickness, were higher at 4°C when compared to 15 and 30°C. The variations of proteins measured by RM confirmed the importance of proteins during the formation of a mature biofilm. Comparative proteomic analysis showed that siderophore and iron chelate transport proteins were down-regulated during mature biofilm formation. The down-regulated aforementioned proteins are involved in promoting iron storage in response to a higher demand for metabolic energy, whereas, the upregulated proteins of the sulfur relay system, pyrimidine metabolism, and purine metabolism are related to bacterial adaptability. Synthesis of proteins related to cold stress was increased and proteins involved in aminoacyl-tRNA biosynthesis were up-regulated, whereas, proteins involved in aminopeptidase activity were down-regulated. Proteolysis to scavenge energy was reduced as proteins involved in pyrophosphatase activity were up-regulated. Also extracellular eDNA was found which may play an important role in maintaining the stability of mature S. putrefaciens biofilm structures under cold stress. This work provides a better understanding of the role of proteins in mature biofilms. In addition, the biofilm formation mechanism of a psychrotrophic spoilage bacterial species at low temperature is explored, which may contribute to generating biofilm controlling strategies during seafood preservation and processing.

Hyperbaric storage at room like temperatures as a possible alternative to refrigeration: evolution and recent advances

From 2012, the preservation of food products under pressure has been increasingly studied and the knowledge acquired has enlarged since several food products have been studied at different storage conditions. This new food preservation methodology concept called Hyperbaric Storage (HS) has gain relevance due to its potential as a replacement or an improvement to the conventional cold storage processes, such as the traditional refrigeration (RF), or even frosting, from the energetic savings to the reduction of the carbon foot-print. Briefly, HS is capable to inhibit the microbial proliferation or its inactivation which results in the extension of the shelf-life of several food products when compared to RF. Moreover, the overall quality parameters seem not to be affected by HS, being the differences detected on samples over storage similar to lower when compared to the ones stored at RF. This review paper aims to gather data from all studies carried out so far regarding HS performance, mainly at room temperature on fruit juices, meat and fisheries, as well on dairy products and ready-to-eat meals. The HS advantages as a new food preservation methodology are presented and explained, being also discussed the industrial viability and environmental impact of this methodology, as well its limitations.