Marios Mataragas

• Senior Researcher at National Agricultural Research Foundation

The activities of sourdough lactic acid bacteria that have been associated with the promotion of consumer health, has been in the epicenter of intensive research over the last decade. Thus, a series of related strain-dependent features has been described. Acidification results in the improvement of starch digestibility, while proteolytic activities...

The use of edible and biodegradable films and coatings as active packaging for cheese has recently attracted great attention as it meets the concept of sustainability and ensures safety. Spirulina is a rich source of high-added-value biocompounds, which could be used as functional ingredients. In the present study, spirulina was added in different...

Dairy products play a crucial role in human nutrition as they provide essential nutrients. However, the presence of diverse microorganisms in these products can pose challenges to food safety and quality. Here, we provide a comprehensive molecular characterization of a diverse collection of lactic acid bacteria (LAB) and staphylococci isolated from...

It is well known that the strong-evidence foodborne outbreaks of human campylobacteriosis are associated with the consumption of raw or incompletely thermally processed poultry meat, whereas broilers act as the main reservoir for Campylobacter species. Campylobacter jejuni and Campylobacter coli are the two main species of campylobacters detected i...

It is well known that the strong-evidence foodborne outbreaks of human campylobacteriosis are associated with the consumption of raw or incompletely thermally processed poultry meat, whereas broilers act as the main reservoir for Campylobacter species. Campylobacter jejuni and Campylobacter coli are the two main species of campylobacters detected i...

Listeriosis is a serious infectious disease with one of the highest case fatality rates (ca. 20%) among the diseases manifested from bacterial foodborne pathogens in humans, while dairy products are often implicated as sources of human infection with Listeria monocytogenes. In this study, we characterized phenotypically and genetically by whole-gen...

Lactic acid bacteria (LAB) are valuable for the production of fermented dairy products. We investigated the functional traits of LAB isolated from artisanal cheeses and raw sheep milk, assessed their safety status, and explored the genetic processes underlying the fermentation of carbohydrates. Lactiplantibacillus plantarum had the largest and more...

Strains belonging to the Weissella genus are frequently recovered from spontaneously fermented foods. Their functional, microbial-modulating, and probiotic traits enhance not only the sensorial properties but also the nutritional value, beneficial effects, and safety of fermented products. Sporadic cases of opportunistic pathogenicity and antibioti...

Enterococci are commensal organisms that have probiotic effects for their hosts and can be used as adjunct cultures in fermented dairy products. The dark side of Enterococci is manifested in E. faecium and E. faecalis, which are the causative agents of nosocomial infections, and thus Enterococci have not been granted a safety status as food additiv...

Listeriosis is a serious infectious disease with one of the highest case fatality rates (i.e., 20-30%) among the bacterial pathogens encountered in foods. In this study, we characterized 54 Listeria monocytogenes strains isolated from a Greek traditional whey cheese (‘Myzithra’) (48 isolates) and swabs sampled from cheese processing surfaces (6 iso...

The aim of the present study was to assess the antimold capacity of three Wickerhamomyces anomalus strains, both in vitro and in situ, and to identify the responsible volatile organic compounds. For that purpose, two substrates were applied; the former included brain heart infusion broth, adjusted to six initial pH values (3.5, 4.0, 4.5, 5.0, 5.5,...

The comparative genome analysis of six Lactiplantibacillus plantarum subsp. argentoratensis strains previously isolated from spontaneously fermented Greek wheat sourdoughs is presented. Genomic attributes related to food safety have been studied according to the European Food Safety Authority (EFSA) suggestions for the use of lactic acid bacteria (...

The aim of the present study was to examine 189 LAB strains belonging to the species Enterococcus faecium, E. faecalis, Lactococcus lactis, Pediococcus pentosaceus, Leuconostoc mesenteroides, Lactiplantibacillus pentosus, Latilactobacillus curvatus, Lp. plantarum, Levilactobacillus brevis, and Weissella paramesenteroides isolated form sheep milk, F...

Fermentation has been of great interest for humans since antiquity and has been extensively used in all cultures worldwide [...]

Artisanal cheesemaking is still performed using practices and conditions derived from tradition. Feta and Kefalograviera cheeses are very popular in Greece and have met worldwide commercial success. However, there is a lack of knowledge regarding their lactic acid microecosystem composition and species dynamics during ripening. Thus, the aim of the...

The aim of the present study was to assess the effect of sourdough related parameters on the growth and plantaricin activity of six Lactiplantibacillus plantarum strains against a mixture of 5 Listeria monocytogenes strains and to analyze the transcriptomic response of their pln genes. Parameters included 3 substrates (MRS broth, mMRS broth, WFE),...

Active packaging can be utilized to keep away from undesirable microbes on the surface of the cheese, prolong its shelf life, and improve its quality. The objective of this study was to use whey protein concentrate (WPC) and aqueous rosemary and sage extracts to produce active edible packaging materials. The antioxidant activity of the extracts was...

In the last decades, edible films based on whey proteins have become promising eco-friendly materials that can be used as carriers for some bioactive substances such as nutrients and antioxidant agents. Spirulina, one of the best-known cyanobacteria, are a rich source of nutritional compounds with beneficial health effects. Edible films from whey p...

Listeria monocytogenes is the bacterial causative agent of listeriosis, a life-threatening disease for humans, mainly transmitted through contaminated food. Human clinical isolates of the pathogen are frequently identified as serotype 4b strains; interestingly, however, serotype 4b (lineage I) is normally underrepresented among the food isolates in...

Lactiplantibacillus plantarum is a species found in a wide range of foods and other commodities. It can be used as starter or adjunct culture in fermented foods. Herein the annotated high-quality draft genome (scaffolds) of six L. plantarum subsp. argentoratensis strains (LQC 2320, LQC 2422, LQC 2441, LQC 2485, LQC 2516 and LQC 2520) isolated from...

The aim of the present study was to assess the technological and safety potential of 207 lactic acid bacteria (LAB) and 195 yeast strains isolated from spontaneously fermented Greek wheat sourdoughs. More accurately, the amylolytic, proteolytic, lipolytic, phytase and amino acid decarboxylase activities, along with the production of exopolysacchari...

The aim of the present study, conducted under the ERA-NET ARIMNet2 Project (Agricultural Research in the Mediterranean Network), was to analyze the sheep and goat dairy sector and assess the quality and safety of milk at various stages of the dairy supply chain. The study took place in the north-west part of Greece; 52 farms, one milk collection ce...

Spirulina platensis, the most popular microalgae species known for its high protein content and bioactive compounds such as phycocyanin and allophycocyanin, has been studied for cheese fortification. Incorporation of spirulina in dairy products poses major sensorial challenges due to its characteristic odor and its insolubility in food formulation,...

The aim of the present study was to assess the microecosystem of 13 homemade spontaneously fermented wheat sourdoughs from different regions of Greece, through the combined use of culture-dependent (classical approach; clustering by Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) and identification by PCR species-specific for...

Kashkaval of Pindos cheeses were produced either with sheep (100%) or mixture of sheep (90%) - goat (10%) milk. Sheep milk cheeses were manufactured either by dry salting or by immersion in 18% w/w salt (NaCl) brine. Cheeses made with the mixture of sheep- goat milk were directly immersed in brine of 15% or 18% w/w NaCl concentration. These are com...

Kashkaval of Pindos cheese was successfully produced using 100% sheep milk (KS) or with the addition of 10% goat milk (KG). Urda cheese was manufactured using 100% sheep (US) or 90% sheep–10% goat (UG) whey from the production of kashkaval of Pindos cheese. Both cheeses were made taking into account their traditional cheese-making methods. The chee...

It is well known that culture media used for the detection of foodborne pathogens are imperfect tests and different media present different sensitivity and specificity values. The present study aimed to estimate the performance of four culture media commonly used for enumerating and detecting Campylobacter in foods. Samples of naturally contaminate...

Genetic diversity and metabolic properties of Lactococcus lactis subsp. lactis were explored using phylogenetic, pan-genomic and metatranscriptomic analysis. The genomes, used in the current study, were available and downloaded from the GenBank which were primarily related with microorganisms isolated from dairy products and secondarily from other...

The aim of the present study was to assess the transcription of the plnE/F, plnN, plnG, plnD and plnI genes during lactic acid fermentation of radish (Raphanus sativus) roots by Lactobacillus plantarum strain LQC 740 at 20 and 30 °C. At both temperatures, this strain dominated the fermentation process, as indicated by (GTG)5 analysis. A total of fi...

Time Temperature Indicators (TTIs) constitute smart devices through which the full history of the time-temperature profile of a food is monitored. The objective of the current study was to develop a versatile microbial TTI based on the violacein formation, a violet pigment produced by the microorganism Janthinobacterium sp. during early growth, dep...

The recent advances in molecular biology, such as the advent of next-generation sequencing (NGS) platforms, have paved the way to new exciting tools which rapidly transform food microbiology. Nowadays, NGS methods such as 16S rDNA/rRNA metagenomics or amplicon sequencing are used for the taxonomic profiling of the food microbial communities. Althou...

Bacteriocins are antimicrobial compounds synthesized by ribosomes. In the last years a variety of bacteriocins, produced by lactic acid bacteria, has been identified and characterized. As a result of these studies is that new knowledge regarding the biosynthesis, structure, production and mode of action of these proteinaceous compounds has been gai...

Lactic acid bacteria produce a variety of small molecular weight compounds, which have antimicrobial properties. Such substances are: organic acids, alcohols, carbon dioxide, diacetyl, hydrogen peroxide and bacteriocins. Many of these compounds have a wide inhibitory spectrum but the bacteriocins are able to inhibit species, namely, related with th...

The development of a multi-omics approach has provided a new approach to the investigation of microbial communities allowing an integration of data, which can be used to better understand the behaviour of and interactions between community members. Metagenomics, metatranscriptomics, metaproteomics and metabolomics have the potential of producing a...

The aim of the present study was to assess the microecosystem development and the dynamics of the lactic acid bacteria population during spontaneous fermentation of radish (Raphanus sativus L.) roots in brine at 20 and 30 °C. In both temperatures, lactic acid bacteria prevailed the fermentation; as a result, the pH value was reduced to ca. 3.6 and...

The role of the fermentation process of fermented foods is twofold, contributing not only to the organoleptic characteristics of the products but also to its stability. Usually, to ensure a satisfactory fermentation and to control the growth of food-borne pathogens, the use of specific starters is recommended. Challenge tests are useful because the...

The aim of the present study was to assess the transcriptomic response of L. monocytogenes isolates on the exposure to lemongrass essential oil. Overnight culture of six strains previously isolated from a strawberry sample was spread over the surface of BHI agar and exposed to 5 and 10 μL of lemongrass essential oil that were applied on a Whatman p...

Abstract for the poster presented at the "IAFP's 12th European Symposium on Food Safety" in Athens, Greece, concerning the performance of culture media used for Campylobacter spp. enumeration in chicken meat samples.

Introduction: The genus Campylobacter consists of significant thermophilic bacterial foodborne pathogens. The International Organization for Standardization (ISO) recommends the use of modified charcoal cefoperazone deoxycholate agar (mCCDA) for Campylobacter enumeration (ISO/TS 10272-2:2006), nevertheless alternative plating methods encompassing t...

The aim of the present study was to assess the expression of key virulence genes, during growth of a Listeria monocytogenes isolate in liquid medium, on melon and rocket at different temperatures and time. For that purpose, BHI broth, rocket and melon were inoculated at 7.0-7.5 log CFU mL-1 or g-1and stored at 4, 10 and 30 °C. Sampling took place u...

In situ quantitative data on Listeria monocytogenes survival during storage of vacuum-packaged fermented sausages at various temperatures were collected from the literature to develop a generic predictive model regarding its fate at a specific storage temperature. The development of the tool was based on the z-concept. The time needed for 4D reduct...

Data relative to in situ Listeria monocytogenes inactivation in fermented sausages were collected from 13 individual studies found in the literature. Inactivation rates were extrapolated and used to develop a predictive model to evaluate the relative effects of pH, water activity (a(w)) and temperature on L monocytogenes fate during fermentation an...

The aims of the present study were to determine the prevalence and levels of Listeria monocytogenes and Escherichia coli O157:H7 in rocket and cucumber samples by deterministic (estimation of a single value) and stochastic (estimation of a range of values) approaches. In parallel, the chromogenic media commonly used for the recovery of these microo...

Fermentation is the most important killing step during production of fermented meats to eliminate food-borne pathogens. The objective was to evaluate whether the food-borne pathogens Listeria monocytogenes and Salmonella enterica may survive during the production of two Italian fermented sausages. Sausage batter was inoculated with five strains of...

Die Zielsetzung bestand darin, die Überlebensfähigkeit der durch Lebensmittel übertragbaren Pathogene Listeria (L.) monocytogenes und Salmonella (S.) enterica bei der Herstellung von Salami vom Typ Cacciatore, Felino und Milano zu bestimmen und ihre Persistenz zu quantifizieren. Die Wurstmasse jeden Wursttyps wurde mit einer Mischung aus fünf Stämm...

The aim of this study was to assess serotype prevalence and biodiversity of Listeria monocytogenes strains isolated from diverse food products, i.e., minced pork, fruits, and vegetables. Three hundred twenty-six samples previously purchased from supermarkets and street markets within the Athens area were studied for L. monocytogenes prevalence. A t...

Abstract in the book of abstracts for the poster presented at the "17th World Congress of Food Science and Technology & Expo: Research that Resonates" in Montreal, Canada, relevant to the Listeria monocytogenes serovar prevalence and dominance dynamics for certain serovars of the pathogen isolated during storage of a ready-to-eat (RTE) meat product...

a) Introduction & Objectives: There are currently 13 known serovars for Listeria monocytogenes, with serovar 1/2a, 1/2b, 1/2c, and 4b strains within this species being responsible for the vast majority (>98%) of the reported human foodborne listeriosis cases. However, human clinical isolates of the pathogen which are usually identified as serovar 4...

A Listeria monocytogenes subgenomic array, targeting 54 genes involved in the adhesion, adaptation, intracellular life cycle, invasion, and regulation of the infection cycle was used to investigate the gene expression patterns of acid- and salt-stressed Listeria cells after exposure to conditions similar to those in gastric and pancreatic fluids. T...

Purpose – The aim of this study is to evaluate the food safety management system (HACCP – type system) implemented in Greek food businesses, examine the techno-managerial factors influencing its application according to enterprises' opinion and correlate these answers to the HACCP evaluation results. Design/methodology/approach – The study involve...

Listeria monocytogenes poses a serious threat to public health, and the majority of cases of human listeriosis are associated with contaminated food. Reliable microbiological testing is needed for effective pathogen control by food industry and competent authorities. The aims of this work were to estimate the prevalence and concentration of L. mono...

The aim of this study was to assess the microbiological quality and the ability of Listeria monocytogenes and Salmonella enterica serovar Typhimurium strains to survive during storage at 4 °C of all available brand names of brined pickles and some in-bulk ones, in the district of Athens. None of the samples could be characterized as heavily contami...

In meat slaughterhouses, the enumeration of certain microorganisms as microbiological quality indicators is very important for verifying effectiveness of the Good Hygiene Practices (GHP) and Hazard Analysis Critical Control Points (HACCP) systems. Microbiological testing of final products as part of the HACCP verifying process may provide informati...

In the present study, the development of reverse transcription-quantitative polymerase chain reaction protocols for three virulence genes (plcA, iap and hly) and the sigB stress response gene that may be applied for the determination of the virulence gene expression of Listeria monocytogenes in situ was reported. When applied to L. monocytogenes st...

Minced pork samples (n = 150) obtained from butchers' shops and supermarkets in Greece, during summer (n = 75) and winter (n = 75), were subjected to microbiological analysis. Microbial counts (log CFU/g) for the parameters tested were: total viable count (TVC), 6.8 ± 1.0; Pseudomonas spp., 6.4 ± 1.2; Brochothrix thermosphacta, 5.9 ± 1.1; lactic ac...

In recent years and with the significant advancements in instrumentation for molecular biology methods, the focus of food microbiologists, dealing with pathogenic microorganisms in foods, is shifting. Scientists specifically aim at elucidating the effect that the food composition, as well as the commonly employed preservation/storage techniques thr...

Three low-fatty baby food matrices were fortified with 0.01-0.2 mg/kg of phorate, diazinon, chlorpyrifos and methidathion. A "quick, easy, cheap, effective, rugged and safe" - like method (QuEChERS) was used. Quantities of octadecyl (C-18) sorbent differed with fortification level and matrix fat, based on central composite experimental design. Quan...

A subgenomic array, encompassing 54 probes targeting genes responsible for virulence, adhesion and stress response in Listeria monocytogenes, was used in order to study their expression in food systems. RNA extracted from L. monocytogenes inoculated in BHI and in situ (i.e. in minced meat and fermented sausage juices) and incubated at 4°C, was hybr...

Adrenal steroid profiling, including 17α-OH progesterone (17OHP), 11-deoxycortisol (S), Δ4-androstenedione (Δ4-A) and cortisol (F) in blood spots by tandem mass spectrometry, is used for newborn screening to detect congenital adrenal hyperplasia (CAH). Pre-analytical sample processing is critical for assay specificity and accuracy; however, it is l...

The aim of the present study was to develop a predictive model to quantify the spoilage of yoghurt with fruits. Product samples were stored at various temperatures (5-20 °C). Samples were subjected to microbiological (total viable counts, lactic acid bacteria-LAB, yeasts and moulds) and physico-chemical analysis (pH, titratable acidity and sugars)....

Food safety assessment has been originally performed by traditional culture-dependent microbiological techniques. These techniques, although simple and inexpensive, they are laborious, time-consuming and very often misleading. Advancements in the field of molecular biology allowed the development of more sophisticated techniques that enabled safety...

The aim of this study was to quantify the hygienic status of a lamb slaughterhouse by means of multivariate statistical analysis, to demonstrate how the microbiological data could be exploited to improve the lamb slaughter process by constructing control charts and to evaluate the potential effect of an intervention step such as steam application o...

The aim of the study was to investigate and establish the microbial association of minced pork meat by applying multivariate analysis. Samples (n=150) obtained from butcher’s shops (n=127) and super markets (n=23), during winter (n=75) (November to March) and summer (n=75) (May to September) were subjected to microbiological analysis: Total Viable...

The presence of Listeria monocytogenes in a sliced cooked, cured ham-like meat product was quantitatively assessed. Sliced cooked, cured meat products are considered as high risk products. These ready-to-eat, RTE, products (no special preparation, e.g. thermal treatment, before eating is required), support growth of pathogens (high initial pH=6.2-6...

Cheeses, even though characterized as safe for consumption, have been implicated in foodborne outbreaks associated with severe symptoms and high fatality rate. The foodborne pathogens in raw milk originate from the farm environment and direct excretion from animals infected udder, whereas in dairy plants the pathogens may enter via contaminated raw...

The use of antimicrobials is a common practice for preservation of foods. Incorporation, in a food recipe, of chemical antimicrobials towards inhibition of spoilage and pathogenic micro-organisms results in the compositional modification of food. This treatment is nowadays undesirable for the consumer, who likes natural products. Scientific communi...

In the present work, survival of Listeria monocytogenes in the traditional Greek soft, spreadable cheese Katiki was studied throughout the shelf life of the product. Samples of finished cheese were inoculated with a cocktail of five L. monocytogenes strains (ca. 6 log CFU g(-1)) and stored at 5, 10, 15, and 20 degrees C. Acid-stress adaptation or c...

Steroid determination by immunoassays results in significant interferences and inaccurate results. This study describes the development and validation of a new gas chromatographic-mass spectrometric method for the simultaneous quantification of 17alpha-hydroxyprogesterone (17alphaOHP), testosterone (T), dehydroepiandrosterone (DHEA), androstenedion...

Risk profiles of pork and poultry meat were carried out using an Excel-based software program, Risk Ranger. It is a semi-quantitative risk estimator answering various questions relating to the probability of exposure to a hazard, susceptibility of the population of interest, severity of the illness caused by the hazard if present and probability of...

Bacteriocins are peptides or proteins that exert an antimicrobial action against a range of microorganisms. Their production can be related to the antagonism within a certain ecological niche, as the producer strain, being itself immune to its action, generally gains a competitive advantage. Many Gram-positive and Gram-negative microorganisms have...

A cooked, cured meat product is a perishable product spoiled mainly by lactic acid bacteria (LAB). LAB cause discoloration, slime formation, off-odors and off-flavors as the result of their metabolic activity producing various products. These microbial products in conjunction with the microbial population could be used to assess the degree of spoil...

In the present study, the distribution of the shelf life of cooked, cured meat products based on lactic acid bacteria growth and the distribution of the time to cause health risks based on Listeria monocytogenes growth were studied. Growth models, developed and validated on cooked meat products, were used to predict the growth of microorganisms. Te...

Leuconostoc mesenteroides E131, isolated from dry fermented sausages, produces an antimicrobial agent, characterized as bacteriocin. The effect of pH and temperature on growth and bacteriocin production, using MRS broth as growth medium, was studied in a fermentor. The pH value at which the best cell growth was observed (6.5) did not coincided with...

Listeria monocytogenes NCTC10527 was examined with respect to its nonthermal inactivation kinetics in fermented sausages from four European countries: Serbia-Montenegro, Hungary, Croatia, and Bosnia-Herzegovina. The goal was to quantify the effect of fermentation and ripening conditions on L. monocytogenes with the simultaneous presence or absence...

The food-borne pathogen Bacillus cereus can acquire enhanced thermal resistance through multiple mechanisms. Two Bacillus cereus strains, ATCC 10987 and ATCC 14579, were used to quantify the effects of salt stress and physiological state on thermotolerance. Cultures were exposed to increasing concentrations of sodium chloride for 30 min, after whic...

  In the present study, the spoilage flora of a sliced cooked cured meat product was studied to determine the specific spoilage organism (SSO). The physicochemical changes of the product during its storage in a temperature range of 0 to 12 °C were also studied. Among the primary models used to model the temperature effect on SSO growth, the modifie...

To describe the growth limits of Listeria monocytogenes NCTC10527 in a sliced vacuum-packaged cooked cured meat product, the binary logistic regression model was used to develop an equation to determine the probability of growth or no growth of L. monocytogenes as a function of temperature (from 0 to 10 degrees C) and water activity (from 0.88 to 0...

Lactobacillus curvatus, isolated from a spoiled vacuum-packaged 'pariza' type meat product, was used to inoculate modified MRS broth containing sodium lactate, sodium acetate and potassium sorbate in different concentrations, alone or in inter se combinations. Two commercial preparations (MIX 1 and MIX 2) were also used containing combinations of t...

The microbial flora of naturally fermented sausages was studied. Lactic acid bacteria were the dominant species at the end of fermentation in all 3 batches (ca. 10(8) cfu g(-1)). Enterobacteria, Pseudomonas, yeasts and aerobic spore-formers decreased during fermentation and the ripening process and were below the detection limit in the end product....

The aim of this study was to investigate the effect of pH, temperature, sodium chloride, type and level of sugar used in fermented sausages, on the occurrence and the concentration of the maximum bacteriocin activity, in order to optimize the bacteriocin synthesis during the growth cycle of Leuconostoc mesenteroides E131. In order to study the effe...

The aim of this study was to investigate the effect of complex nutrients on microbial growth and bacteriocin production, in order to improve bacteriocin synthesis during the growth cycle of Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442. The fermentations were conducted at the optimum pH and temperature for bacteriocin production (p...

The aim of this study was to investigate the relationship between the microbial growth, the bacteriocin production and the effect of pH and temperature on the occurrence and the concentration of the maximum activity, to optimize the bacteriocin synthesis during the growth cycle. Two bacteriocins produced by lactic acid strains Leuconostoc mesentero...

Lactic acid bacteria (LAB) strains, isolated from dry fermented sausages were tested as protective cultures in vacuum- or modified atmosphere-packaged sliced cooked cured pork shoulder at 4°C. The inhibitory capacity of the bacteriocins produced by Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442 against different strains of Listeria...

Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442, isolated from dry fermented sausages, produce bacteriocins antagonistic towards closely related species and pathogens, such as Listeria monocytogenes. The bacteriocins were inactivated by proteolytic enzymes and lipase but not by catalase and lysozyme. They were also heat stable, retai...

To investigate the antagonistic activity of two lactic acid strains against the spoilage microflora in cooked cured meat products, vacuum or modified atmosphere packed at 4 degrees C and to determine the inhibitory capacity of their bacteriocins. Frankfurter-type sausages and sliced cooked cured pork shoulder were inoculated with Leuconostoc mesent...