Food Pathogenic Microorganisms Research Articles

Synthesis of dual models multivalent activatable aptamers based on HCR and RCA for ultrasensitive detection of Salmonella typhimurium

Aptamers have superior structural properties and have been widely used in bacterial detection methods. However, the problem of low affinity still exists in complex sample detection. In contrast, hybridization chain reaction (HCR)-based model I and rolling circle amplification (RCA)-based model II multivalent activatable aptamers (multi-Apts) can fulfill the need for low-cost, rapid, highly sensitive and high affinity detection of S. typhimurium. In our research, two models of multi-Apts were designed. First, a monovalent activatable aptamer (mono-Apt) was constructed by fluorescence resonance energy transfer (FRET) with an S. typhimurium aptamer and its complementary chain of BHQ1. Next, the DNA scaffold was obtained by HCR and RCA, and the multi-Apts were obtained by self-assembly of the mono-Apt with a DNA scaffold. In model I, when target was presented, the complementary chain BHQ1 was released due to the binding of multi-Apts to the target and was subsequently adsorbed by UIO66. Finally, a FRET-based fluorescence detection signal was obtained. In mode II, the multi-Apts bound to the target, and the complementary chain BHQ1 was released to become the trigger chain for the next round of amplification of HCR with a fluorescence detection signal. HCR and RCA based multi-Apts were able to detect S. typhimurium as low as 2 CFU mL−1 and 1 CFU mL−1 respectively. Multi-Apts amplification strategy provides a new method for early diagnosis of pathogenic microorganisms in foods.

Application of Taro (Colocasia esculenta) Mucilage as a Promising Antimicrobial Agent to Extend the Shelf Life of Fresh-Cut Brinjals (Eggplants).

Taro rhizomes are a rich source of polysaccharides, including starch and mucilage. However, mucilage has excellent anti-microbial efficacy, and unique gel-forming and techno-functional properties. Therefore, this study aimed to extract and utilize taro mucilage (TM), which is viscous and has a gel-like texture, for the shelf-life enhancement of fresh-cut brinjals (eggplants). Mucilage was extracted using hot-water extraction and the yield was calculated to be 6.25 ± 0.87% on a dry basis. Different formulations of coating gel solutions were prepared: 1, 2, 3, 4, 5, 6, and 7%. The selection of the coating gel solution was carried out based on particle size. The smallest particle size was observed in treatment T5 (154 ± 0.81 nm) and zeta potential -27.22 ± 0.75 mV. Furthermore, cut brinjals were coated with the prepared mucilage gel solution and this showed a significant effect on the overall physicochemical properties of cut brinjals. Maximum weight loss occurred on the 10th day (12.67 ± 0.24%), as compared with coated brinjals (8.99 ± 0.42%). Minor changes were observed in pH, for the control sample significantly decreased from 4.58 ± 0.45 to 2.99 ± 0.75 on the 0th day to the 10th day, respectively. Titrable acidity of coated and uncoated cut brinjals was found to be at 0.31 ± 0.44% on the 0th day, which increased up to 0.66 ± 0.20% for the control and 0.55 ± 0.68% for coated brinjals on the 10th day. The taro mucilage coating gel (TMCG) solution showed pseudo-plastic behavior or shear-thinning fluid behavior. FTIR data confirmed the existence of several functional groups including various sugars, proteins, and hydroxylic groups. Antioxidant activity of coated and uncoated cut brinjals was found to be 22.33 ± 0.37% and 22.15 ± 0.49%, respectively. The TMCG solution showed effective results towards the various food pathogenic microorganisms. Overall, it is a natural, renewable resource that is biodegradable. This makes it an environmentally friendly alternative to synthetic additives or thickeners. It is cost effective, easily available, eco-friendly, and non-toxic. This can be an attractive feature for consumers looking for sustainable and eco-friendly options.

Process optimization for spray dried Aegle marmelos fruit nanomucilage: Characterization, functional properties, and in vitro antibiofilm activity against food pathogenic microorganisms

Recently, mucilage extraction from plant sources has been remarkably explored due to its potential applications. Several underutilized fruits such as Aegle marmelos are the potential source of mucilage that can be utilized for agri-food-pharma applications. Therefore, in this study, we explored vital functional and antimicrobial properties of Aegle marmelos nanomucilage. Spray drying conditions such as inlet temperature, feed flow, and atomization speed were optimized to assess the influence on yield and moisture content using response surface methodology. In addition, during the optimized spray drying conditions, the maximum mucilage yield was 16.23 % (w/w). The particle size (178.4 ± 5.06 nm) at the nanoscale, polydispersity index (0.432), and zeta potential (−16.4 ± 1.14 mV) confirmed the stability of the nanomucilage. Moreover, the spray-dried nanomucilage powder exhibited high thermal stability (55.70 J) and excellent industrially important techno-functional properties with water-holding capacity (8.01 ± 0.04 g/g), oil-holding capacity (3.43 ± 0.7 g/g), emulsifying capacity (91.50 ± 0.78 %), emulsifying stability (92.65 ± 0.46 %), solubility (89.36 ± 1.69 %), and foaming capacity (16.13 ± 0.41 %). Moreover, the powder showed strong antibiofilm activity against food-pathogenic bacteria, including Escherichia coli (73.52 ± 1.14 %) and Staphylococcus aureus (79.57 ± 1.23 %), with minimum inhibitory concentrations of 3.125 mg/mL and 1.562 mg/mL respectively. Overall, based on the above findings the spray-dried powder of Aegle marmelos fruit nanomucilage could be utilized as a potential functional ingredient in various food products formulations.

Application of Nanopore Sequencing in the Detection of Foodborne Microorganisms.

Foodborne pathogens have become the subject of intense interest because of their high incidence and mortality worldwide. In the past few decades, people have developed many methods to solve this challenge. At present, methods such as traditional microbial culture methods, nucleic acid or protein-based pathogen detection methods, and whole-genome analysis are widely used in the detection of pathogenic microorganisms in food. However, these methods are limited by time-consuming, cumbersome operations or high costs. The development of nanopore sequencing technology offers the possibility to address these shortcomings. Nanopore sequencing, a third-generation technology, has the advantages of simple operation, high sensitivity, real-time sequencing, and low turnaround time. It can be widely used in the rapid detection and serotyping of foodborne pathogens. This review article discusses foodborne diseases, the principle of nanopore sequencing technology, the application of nanopore sequencing technology in foodborne pathogens detection, as well as its development prospects.

Antioxidant properties of medicinal plants and their effect on microbial spoilage of semi-finished meat, poultry and fish

Plant extracts rich in polyphenols can be used in the food industry as natural preservatives, extending the shelf life of prepared and semi-finished foods without chemical preservatives. In this paper, we investigate the polyphenolic composition, antioxidant activity and antibacterial properties of herbal extracts as part of food systems. The research objects were knot grass (Polýgonum aviculáre), marjoram (Oríganum), bur beggar-ticks (Bídenstripartíta), thyme (Thymus), whortleberry leaves (Vaccínium ida vítis), calendula (Calendula), sage (Salvia), chamomile flowers (Matricāriachamomīlla), eucalyptus (Eucalýptus) and bearberry (Arctostáphylosúva-úrsi). We determined the total content of phenolic compounds and flavonoids; the antioxidant activity by DPPH and FRAP methods; variations in the bacterial сontamination of animal raw materials over total bacterial count (TBC), coliform bacteria, yeast/fungi, salmonella and staphylococcus. Extracts of sage (1138±57 mg GA/100 g and 537±25 mg C/100 g), eucalyptus (1073±49 mg GA/100 g and 412±20 mg C/100 g), chamomile flowers (1002±36 mg GA/100 g and 493±22 mg C/100 g) and marjoram (1015±42 mg GA/100 g and 458±21 mg C/100 g) contain the largest amount of biologically active substances (phenols and flavonoids, respectively). Sage, eucalyptus and chamomile extracts demonstrate the highest antioxidant activity among the studied samples. Most of the studied extracts exhibit little or no effect on the organoleptic properties of finished products. In addition, chamomile flower, sage and eucalyptus extracts suppress the growth of pathogenic microorganisms in foods under experimental conditions. The microflora growth is significantly reduced when treating animal raw materials with calendula flowers, marjoram and thyme extracts. Extracts of sage, chamomile flowers, calendula flowers, marjoram and thyme can be recommended as components of food raw materials.

Time-Kill Kinetic Effect of Sodium Citrate, Sodium Nitrite and Cinnamaldehyde Against Biofilm Forming Escherichia coli O157:H7

Food safety is a significant concern of every sector of the food industry. Survival of Escherichia coli O157:H7 with biofilm-forming potential in commercial food premises is a possible danger to consumers’ health, especially in societies where most of the population depend on it for their daily meals. Preservation of fresh food quality being of utmost importance, new innovative means of inhibiting pathogenic microorganisms in foods are being evaluated to be effective at destroying microorganisms and preserving the physical and organoleptic properties. This study aimed to inhibit biofilm formation of Escherichia coli O157:H7 by food additives; sodium citrate, sodium nitrite and cinnamaldehyde. The isolate obtained was subjected to Gram’s staining and various biochemical identifications and later confirmed by the latex agglutination test. The Escherichia coli O157:H7 was further subjected to a biofilm formation potential test on Congo red media. Antimicrobial susceptibility testing was conducted to obtain the susceptibility/resistance pattern of the isolate to the food additives. The MIC, MBC and time-kill kinetics effect was determined following CLSI 2017 guideline. The highest growth inhibition zone of 31 mm was exhibited by cinnamaldehyde, followed by sodium nitrite with 26 mm and sodium citrate with 13 mm. The MIC was determined to be 2.5 mg/ml for sodium citrate, 0.25 mg/ml for sodium nitrite and 0.125 µl/ml for cinnamaldehyde. Sodium citrate was found to be bacteriostatic between 6-8 hrs with 72.9 % reduction, sodium nitrite and cinnamaldehyde exhibit both bacteriostatic and bactericidal effects between 2-24 hrs with percentage inhibition of 65-90 % and 63-100 %, respectively. This study showed that sodium citrate, sodium nitrite and cinnamaldehyde exerted strong antimicrobial properties indicating their potential as suitable preservatives.

Challenge Test as Special Tool to Estimate the Dynamic of Listeria monocytogenes and Other Foodborne Pathogens

Over 23 million cases of foodborne disease (FBD) occur in Europe each year, with over 4700 deaths. Outbreaks of FBD have a significant impact on our society due to the high economic losses they cause (hospital treatment of affected patients and destruction of contaminated food). Among its health objectives, the European Union has set itself the goal of reducing the incidence of the main FBDs, approving various regulations that codify requirements in order to produce food that is “safe” for human consumption. Among these rules, Regulation 2005/2073 establishes precise food safety criteria for foods that are judged to be most at risk of causing episodes of FBD. The food business operator (FBO) must know their food better and know how to estimate whether a food can support the growth of food pathogens or if they are able to hinder it during the food’s shelf life. It is becoming crucial for each FBO to schedule specific laboratory tests (challenge tests) to establish the growth potential of individual pathogens and their maximum growth rate. In 2008 the European Union published the guidelines for programming the challenge tests for Listeria monocytogenes in RTE foods. These guidelines were further implemented in 2014 and again in 2019. In June 2019 the UNI EN ISO 20976-1 was published, which contains indications for setting up and carrying out challenge tests for all foodborne pathogens in all foods. In this article, we compare the three official documents to highlight their common aspects and differences, highlighting the advantages and disadvantages that each of them offers for those who have to set up a challenge test for the various foodborne pathogens. Our conclusion is that the challenge test is today the most effective tool to estimate the dynamics and growth potential of pathogenic microorganisms in food, if it is designed and implemented in a scrupulous way. It is important to develop a rational experimental design for each challenge test, and for each food, and this requires professionals who are experts in this specific field of study and who must be properly trained.

Antimicrobial Properties of Food Nanopackaging: A New Focus on Foodborne Pathogens.

Food products contaminated by foodborne pathogens (bacteria, parasites, and viruses) cause foodborne diseases. Today, great efforts are being allocated to the development of novel and effective agents against food pathogenic microorganisms. These efforts even might have a possible future effect in coronavirus disease 2019 (COVID-19) pandemic. Nanotechnology introduces a novel food packaging technology that creates and uses nanomaterials with novel physiochemical and antimicrobial properties. It could utilize preservatives and antimicrobials to extend the food shelf life within the package. Utilizing the antimicrobial nanomaterials into food packaging compounds typically involves incorporation of antimicrobial inorganic nanoparticles such as metals [Silver (Ag), Copper (Cu), Gold (Au)], and metal oxides [Titanium dioxide (TiO2), Silicon oxide (SiO2), Zinc oxide (ZnO)]. Alternatively, intelligent food packaging has been explored for recognition of spoilage and pathogenic microorganisms. This review paper focused on antimicrobial aspects of nanopackaging and presented an overview of antibacterial properties of inorganic nanoparticles. This article also provides information on food safety during COVID-19 pandemic.

Evaluation of antimicrobial potential and phytochemicals in Acmella ( A. oleracea ) flower pod extracts subjected to different drying techniques

The study was aimed to evaluate how drying methods and extracting solvents can preserve antimicrobial properties of Acmella flower pods. Four drying techniques (sun drying [SD], air drying [AD], oven drying [OD], and cooling with dehumidifying [CWD]) and three different solvent extractions (ethanol extracts [EE], water extracts [WE], and pet ether extracts [PEE]) were employed to evaluate extraction yield (EY), phytochemical analysis, and in vitro antibacterial activity. The highest EY was observed in CWD dried WE. Alkaloids, tannin, and quinone were detected in all extracts while flavonoid only in SD and CWD dried EE. CWD dried WE comprised all tested phytochemicals, except flavonoids. CWD dried WE showed higher zones of inhibitions (ZOI) 18.8, 14.0, 12.0, 20.2, and 17.3 mm for Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans, respectively. CWD dried pod extracts showed higher effectivity against bacteria and fungus while lowest given by SD extracts. CWD dried WE gave 20 volatile compounds in GC-MS, including dilauryl thiodipropionate, clionasterol, and spilanthol. Practical applications This study provided a comprehensive evaluation of how the drying method and solvent used for extraction of Acmella oleracea flower pods can effect on the extraction yield, available phytoconstituents, and antimicrobial activity. Through this study, it was recognized that CWD drying followed by water extraction is the best method to preserve antimicrobial potential and bioactive constituents in preserving raw Acmella oleracea flower pods. Phytochemical availability and ability to inhibit Gram-negative, positive bacteria, and fungus is an indication of Acmella flower pods' antimicrobial potential which can be employed to control food pathogenic microorganisms in food industry.

Physico-Chemical and Antiadhesive Properties of Poly(Lactic Acid)/Grapevine Cane Extract Films against Food Pathogenic Microorganisms

The aim of this study was evaluation of the physico-chemical properties and adhesion of microorganisms on poly(lactic acid) (PLA)-based films loaded with grapevine cane extract (5–15 wt%). The films were processed in a compression molding machine and characterized by mechanical, thermal, water vapor barrier and microbiological tests. The best physical-chemical properties for PLA film containing 10 wt% of extract were obtained. The addition of 10 wt% of extract into PLA films led to decrease of tensile strength for 52% and increase in elongation at break for 30%. The water vapor barrier of this film formulation was enhanced for 55%. All films showed thermal stability up to 300 °C. The low release of the active compounds from films negatively influenced their antimicrobial and antifungal activity. Botrytis cinerea growth inhibition onto PLA containing extracts (PLA-E) films was in the range between 15 and 35%. On the other side, PLA/extract films exhibited the antiadhesive properties against Pseudomonas aeruginosa, Pectobacterium carotovorum, Saccharomyces pastorianus, and Listeria monocytogenes, which could imply their potential to be used as sustainable food packaging materials for preventing microbial contamination of food.

Inactivation of Foodborne Pathogens by Lactic Acid Bacteria

The problems caused by foodborne pathogens are not only a concern to the food industry but also with regard to global public health. Over the years, fermentation technology has proved to be one of the cheapest and safest methods for inactivating and controlling pathogenic microorganisms in food. Scientific evidence shows that lactic acid bacteria fermentation exerts significant antimicrobial effect against pathogenic bacteria and viruses. Lactic acid bacteria metabolites such as organic acids, bacteriocins and hydrogen peroxides have adverse effects on foodborne pathogens which lead to their inhibition. These compounds do not only cause physical injuries, but also have significant effects on the pathogens' gene expression. Furthermore, the presence of lactic acid bacteria in food provides nutritional competition among foodborne pathogens, and all these factors together suppress their growth. This study reviews our current knowledge of the antimicrobial abilities of lactic acid bacteria, their molecular mechanisms, and their application for inactivating foodborne pathogens.

Increasing the Shelf Life of Milk by Metal Oxide Nanoparticles and Mild Heat

Background: The spread of pathogenic microorganisms in food and beverage and their resistance to antibiotics have raised major concerns for public health. The aim of this study was to investigate the antimicrobial activity of various metal oxide nanoparticles (NPs) including zinc oxide (ZnO), magnesium oxide (MgO), and iron oxide (Fe2O3) NPs against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Furthermore, the antimicrobial activity of these NPs in milk was studied along with mild heat.
 Methods: In this experimental study, the antibacterial activity of ZnO, MgO, and Fe2O3 NPs were initially evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. Later, the antimicrobial effect of these NPs was investigated in milk along with mild heating. To determine the morphological changes in S. aureus and E. coli, electron microscopy scanning was applied before and after the antimicrobial treatments.
 Results: The MBC and MIC values presented by Fe2O3, ZnO, and MgO NPs against pathogenic bacteria showed that MgO NPs were the most potent substances for inhibiting the growth of S. aureus and E. coli. The results also indicated that use of these NPs had synergistic effects in combination with the heating treatment. Electron microscopy scanning also revealed that treatment with MgO NPs could distort and impair the cell wall of the pathogenic bacteria, leading to the leakage of intracellular components and bacterial death.
 Conclusion: The results suggest that MgO, ZnO, and Fe2O3 NPs can be applied for industrial food processing as effective antimicrobial compounds to decrease the temperature required for pasteurizing milk.

Inactivation of foodborne pathogens by the synergistic combinations of food processing technologies and food-grade compounds.

There is a need to develop food processing technologies with enhanced antimicrobial capacity against foodborne pathogens. While considering the challenges of adequate inactivation of pathogenic microorganisms in different food matrices, the emerging technologies are also expected to be sustainable and have a minimum impact on food quality and nutrients. Synergistic combinations of food processing technologies and food-grade compounds have a great potential to address these needs. During these combined treatments, food processes directly or indirectly interact with added chemicals, intensifying the overall antimicrobial effect. This review provides an overview of the combinations of different thermal or nonthermal processes with a variety of food-grade compounds that show synergistic antimicrobial effect against pathogenic microorganisms in foods and model systems. Further, we summarize the underlying mechanisms for representative combined treatments that are responsible for the enhanced microbial inactivation. Finally, regulatory issues and challenges for further development and technical transfer of these new approaches at the industrial level are also discussed.

Natural Preservatives from Plant in Cheese Making.

Simple SummaryCheese is a food that is susceptible to contamination by pathogenic and spoilage microorganisms, which can result in a reduced cheese shelf life, as well as in risks to the consumers’ health. This implies the possible use of preservatives in the cheese making process. At the same time, consumers are increasingly demanding for healthy food, free from synthetic preservatives. Just for this reason, natural ingredients are receiving increasing attention as substitutes for synthetic additives, also because they have bioactive compounds, which might provide health benefits in the prevention of several diseases. Furthermore, most of natural ingredients have shown antimicrobial activity, which could delay or inhibit the growth of pathogenic microorganisms in food, as well as minimize the incidence of foodborne diseases caused by food spoilage bacteria and fungi. This review aims at discussing the antimicrobial activity of the main natural ingredients derived from plants and used in cheese making, and their effect on cheese quality, in terms of chemical, nutritional and sensory characteristics of the products, as well as the increase in cheese shelf-life.Today, consumers are increasingly demanding safety alternatives concerning the use of synthetic additives in the food industry, as well as healthy food. As a result, a major number of plant-derived preservatives have been tested in the food industry. These natural ingredients have antioxidant properties and have shown to increase the bioactive molecules levels and the microbiological stability of the food items. The effect of the plant-based preservatives on the sensorial properties of the new products has also to be considered, because natural preservatives could result in sensorial characteristics that may not be accepted by the consumers. Cheese is a dairy product widely appreciated all over the world, but it is also susceptible to contamination by pathogenic and spoilage microorganisms; therefore, the use of preservatives in cheese making represents an important step. This review deals with one of the innovation in the cheese sector, which is the addition of natural preservatives. Several aspects are discussed, such as the effect of natural ingredients on the microbial stability of cheese, and their influence on the chemical, nutritional and sensorial characteristics of the cheeses. Although the promising results, further studies are needed to confirm the use of natural preservatives from plants in cheese making.

Gold Nanoparticle-Coated Starch Magnetic Beads for the Separation, Concentration, and SERS-Based Detection of E. coli O157:H7.

Here, we report gold nanoparticle-coated starch magnetic beads (AuNP@SMBs) that were prepared by in situ synthesis of AuNPs on the surface of SMBs. Upon functionalization of the surface with a specific antibody, the immuno-AuNP@SMBs were found to be effective in separating and concentrating the target pathogenic bacteria, Escherichia coli O157:H7, from an aqueous sample as well as providing a hotspot for surface-enhanced Raman scattering (SERS)-based detection. We employed a bifunctional linker protein, 4× gold-binding peptide-tagged Streptococcal protein G (4GS), to immobilize antibodies on AuNP@SMBs and AuNPs in an oriented form. The linker protein also served as a Raman reporter, exhibiting a strong and unique fingerprint signal during the SERS measurement. The amplitude of the SERS signal was shown to have a good correlation with the concentration of target bacteria ranging from 100 to 105 CFU/mL. The detection limit was determined to be as low as a single cell, and the background signals derived from nontarget bacteria were negligible due to the excellent specificity and colloidal stability of the immuno-AuNP@SMBs and SERS tags. The highly sensitive nature of the SERS-based detection system will provide a promising means to detect the pathogenic microorganisms in food or clinical specimen.

Anti-quorum Sensing and Antimicrobial Effect of Mediterranean Plant Essential Oils Against Phytopathogenic Bacteria.

Essential oils (EOs) are one of the most interesting natural products extracted from different aromatic plants. For centuries, EOs have been considered an essential part of the traditional pharmacopeia. Many plant EOs have been reported as possible effective alternatives for commercial pesticides, and their single constituents have been used efficiently in food preservation for their promising anti-QS activity against several food pathogenic microorganisms. The current mini review gives a general overview over the microbicide effect as well as anti-quorum sensing and the anti-biofilm formation of some common plant EOs, especially those of Lamiaceae and Verbanaceae families; these are commonly grown in the Mediterranean region and are effective against some serious food phytopathogenic bacteria.

Single and multiple detections of foodborne pathogens by gold nanoparticle assays.

A late detection of pathogenic microorganisms in food and drinking water has a high potential to cause adverse health impacts in those who have ingested the pathogens. For this reason there is intense interest in developing precise, rapid and sensitive assays that can detect multiple foodborne pathogens. Such assays would be valuable components in the campaign to minimize foodborne illness. Here, we discuss the emerging types of assays based on gold nanoparticles (GNPs) for rapidly diagnosing single or multiple foodborne pathogen infections. Colorimetric and lateral flow assays based on GNPs may be read by the human eye. Refractometric sensors based on a shift in the position of a plasmon resonance absorption peak can be read by the new generation of inexpensive optical spectrometers. Surface-enhanced Raman spectroscopy and the quartz microbalance require slightly more sophisticated equipment but can be very sensitive. A wide range of electrochemical techniques are also under development. Given the range of options provided by GNPs, we confidently expect that some, or all, of these technologies will eventually enter routine use for detecting pathogens in food. This article is categorized under: Diagnostic Tools > Biosensing.

‘MicroHibro’: A software tool for predictive microbiology and microbial risk assessment in foods

A tool able to quantitatively assess the fate of potential pathogenic microorganisms in foods along the food chain and their impact on public health is highly valuable for food safety decision-makers. The aim of this work was to present an overview of the Predictive Microbiology software MicroHibro, which is able to assess the evolution of potential pathogens and spoilage microorganisms along the food chain, providing estimates for the exposure level and risk associated with a food product. The application is built on an extensive Predictive Microbiology Model Data Base (PMDB) including kinetic processes like growth, inactivation, transfer as well as dose-response models. PMDB can be populated with new models by using an on-line tool in combination with a standardized method for describing Predictive Microbiology models. This enables MicroHibro to be easily updated, increasing its applicability and use. Estimation of microbial risk associated with a food product can be achieved, in MicroHibro, by describing steps in any food chain using four different microbial processes (growth, inactivation, transfer and partitioning). As a result, an estimate of the concentration and prevalence of microorganisms in the food of interest as well as attendant risk are provided. Also, MicroHibro allows comparing different predictive models and validate them by introducing user's data. In this paper, examples are provided to illustrate how predictive models can be incorporated in MicroHibro, and then, used to develop a Quantitative Microbial Risk Assessment model. The use of expert computational systems is a powerful tool for supporting food safety and quality activities by Health Authorities and the food industry. They represent a breakthrough in the assessment and management of food safety based on scientific evidence.

Effect of modified atmosphere packaging on the growth of spoilage microorganisms and Listeria monocytogenes on fresh cheese

Queso Fresco has a limited shelf life and has been shown to support the rapid growth of Listeria monocytogenes during refrigerated storage. In addition to improving quality and extending shelf life, modified atmosphere packaging (MAP) has been used to control the growth of pathogenic microorganisms in foods. The objectives of this study were to determine the effects of MAP conditions on the survival and growth of spoilage microorganisms and L. monocytogenes during storage of Queso Fresco manufactured without starter cultures. For L. monocytogenes experiments, cheeses were surface inoculated at ∼4 log10 cfu/g before packaging. Inoculated and uninoculated (shelf life experiments) cheeses were placed in 75-µm high-barrier pouches, packaged under 1 of 7 conditions including air, vacuum, or combinations of N2 and CO2 [100% N2 (MAP1), 30% CO2:70% N2 (MAP2), 50% CO2:50% N2 (MAP3), or 70% CO2:30% N2 (MAP4), 100% CO2 (MAP5)], and stored at 7°C. Samples were removed weekly through 35 d of storage. Listeria monocytogenes counts were determined for inoculated samples. Uninoculated samples were assayed for mesophilic and psychrotolerant counts, lactic acid bacteria, coliforms, and yeast and mold. In general, cheeses packaged under conditions consisting of higher contents of CO2 had lower pH levels during storage compared with those stored in conditions with lower levels or no CO2 at all. Similarly, the antimicrobial efficacy of MAP in controlling spoilage microorganisms increased with increasing CO2 content, whereas conditions consisting of 100% N2, vacuum, or air were less effective. Mean L. monocytogenes counts remained near inoculation levels for all treatments at d 1 but increased ∼2 log10 cfu/g on cheeses packaged in air, vacuum, and 100% N2 (MAP1) conditions at d 7 and an additional ∼1.5 log10 cfu/g at d 14 where they remained through 35 d. In contrast, treatments consisting of 70% CO2 (MAP4) and 100% CO2 (MAP5) limited increases in mean L. monocytogenes counts to <1 log10 cfu/g through 14 d and ∼1.5 log10 cfu/g by d 21. Mean L. monocytogenes counts increased to levels significantly higher than inoculation (d 0) on cheeses stored in MAP2 and MAP3 on d 21, on d 28 for MAP4, and on d 35 for cheeses stored under MAP5 conditions. Overall, significant treatment × time interactions were observed between air, vacuum, and MAP1 when each was compared with MAP2, MAP3, MAP4, and MAP5. These data demonstrate that packaging fresh cheese under modified atmospheres containing CO2 may be a promising approach to extend shelf life while limiting L. monocytogenes growth during cold storage.

Electroflotation of Escherichia coli Improves Detection Rates by Loop-Mediated Isothermal Amplification

Abstract. The power of portable molecular diagnostic systems for detection of pathogenic microorganisms in food and environmental samples is largely limited by small assay volumes (typically 1 to 5 µL), making direct detection of trace contamination (i.e., &amp;lt;104 CFU mL-1) unreliable. To improve detection limits for pathogens dispersed on an ecological scale, we developed a portable point-of-care (POC) sample preparation system using electroflotation (EF) to recover small quantities of these organisms from samples of hundreds of milliliters. Electrolysis reactions, supported on platinum-coated titanium electrodes, generate hydrogen and oxygen microbubbles that impel and displace suspended cells into a recovered concentrate. Samples were prepared by inoculating 380 mL of sterilized phosphate buffer (0.1 M, pH 6.6) with stock culture of ATCC 25922 to final concentrations ranging from 102 to 104 CFU mL-1. Samples were subjected to 10, 15, and 20 min durations of EF treatment under high and low turbulence conditions. We used a loop-mediated amplification (LAMP) assay with primers targeting a single-copy gene (glycerate kinase) in generic to evaluate the effects of EF treatment on concentration and recovery of detectable cell material. LAMP failed to detect in all untreated (control) samples at concentrations below 104 CFU mL-1 but was able to detect in 102 CFU mL-1 samples subjected to various conditions of EF treatment. Two-way ANOVA showed significant differences in detection rates between EF treatment durations for both high (p = 0.0019) and low turbulence (p = 0.002). Dunnett’s multiple comparison tests identified five process conditions resulting in significant (p &amp;lt; 0.05) differences in detection between treatments and the control. Keywords: Biotechnology, Electrolysis, Food pathogens, Microbubbles, Molecular diagnostics, Pathogen detection, POC sample preparation.