
Frédéric LeroyVrije Universiteit Brussel | VUB · Industrial Microbiology (IMDO)
Frédéric Leroy
MSc Bio-engineering, PhD in Applied Biological Sciences
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186
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Introduction
See also: http://we.vub.ac.be/nl/frederic-leroy
As a bio-engineer, Leroy obtained a PhD at the Vrije Universiteit Brussel in 2002, where he continued his career. His research deals with the ecology and functionalities of bacterial communities in (fermented) foods, focussing on animal products. Also, his interests relate to human and animal health and wellbeing, and to aspects of tradition and innovation in food, both from a technological and societal perspective.
Additional affiliations
Education
October 2001 - June 2002
February 1998 - February 2002
October 1992 - June 1997
Publications
Publications (186)
The act of animal killing affects the human psyche in manners that are culturally contingent. Throughout history, societal attitudes towards the taking of animal lives have mostly been based on deference and/or dominion. Postdomestic societies have evolved in fundamentally different ways. Meat production is abundant yet concealed, animals are categ...
Mainstream dietary recommendations now commonly advise people to minimize the intake of red meat for health and environmental reasons. Most recently, a major report issued by the EAT-Lancet Commission recommended a planetary reference diet mostly based on plants and with no or very low (14 g/d) consumption of red meat. We argue that claims about th...
Humanity’s main societal and epistemic transitions also mirror changes in its approach to the food system. This particularly holds true for human–animal interactions and the consumption of animal source foods (red meat especially, and to a lesser degree dairy, eggs, poultry, and fish). Hunter-gathering has been by far the longest prevailing form of...
Background
Staphylococcus shinii appears as an umbrella species encompassing several strains of Staphylococcus pseudoxylosus and Staphylococcus xylosus. Given its phylogenetic closeness to S. xylosus, S. shinii can be found in similar ecological niches, including the microbiota of fermented meats where the species may contribute to colour and flavo...
Consumers of meat and milk products are interested in the connection between agricultural practices and the wellbeing of livestock. Consumers are also concerned about the impact of livestock products on their own health and wellbeing, with some turning to alternative plant-based protein sources. The connection between agricultural practice and cons...
Despite being part of the now often unfavourably perceived category of processed meats, fermented meats remain of substantial nutritional, economic, and cultural importance in today's foodscapes. This translates into a vast assortment of different products. Fermentation is driven by microorganisms (e.g. in fermented sausages), although the terminol...
Nitrate and nitrite salts perform a versatile role in fermented meats, including the inhibition of food pathogens (in particular proteolytic group I Clostridium botulinum). Despite the increasing interest in clean-label products, little is known about the behaviour of this pathogen in response to the removal of chemical preservatives from fermented...
Nutrient Profiling Systems provide frameworks to assess the healthfulness of foods based on food composition and are intended as inputs into strategies to improve diets. Many Nutrient Profiling Systems are founded on a reductionist assumption that the healthfulness of foods is determined by the sum of their individual nutrients, with no considerati...
Goal and theoretical commentary
A number of recent life cycle assessment (LCA) studies have concluded that animal-sourced foods should be restricted—or even avoided—within the human diet due to their relatively high environmental impacts (particularly those from ruminants) compared with other protein-rich foods (mainly protein-rich plant foods). Fr...
Skerpikjøt is a traditionally ripened sheep leg product from the Faroe Islands, constituting a relatively underexplored microbial ecosystem. The objective of this study is to achieve a deeper understanding of the microbial composition of this artisanal product. Nine ripened hind legs, obtained from three different producers, were assessed regarding...
Analysis of the de novo assembled genome of Mammaliicoccus sciuri IMDO-S72 revealed the genetically encoded machinery behind its earlier reported antibacterial phenotype and gave further insight into the repertoire of putative virulence factors of this recently reclassified species. A plasmid-encoded biosynthetic gene cluster was held responsible f...
Reductionist approaches to food focus on isolated nutritional criteria, ignoring the broader physiological and societal benefits and trade-offs involved. They can lead to the inadvertent or, potentially, intentional labelling of foods as good or bad. Both can be considered worrisome. Among our present-day array of issues is the disproportionate sti...
A recent analysis by Stylianou et al. (2021) estimated the impact of small dietary changes in the consumption of individual foods on human health and the environment, expressed as minutes of healthy life lost or gained daily and dietary carbon footprint, respectively. While an appealing concept for its simplistic interpretation, we propose that thi...
The adoption of carbohydrate-restrictive diets to improve health is increasing in popularity, but there is a dearth of research on individuals who choose to severely restrict or entirely exclude carbohydrates. The present study investigated the beliefs and experiences of individuals following a diet that severely limits, or entirely excludes, dieta...
Per capita meat consumption in post-industrial countries is higher today than it has been ever since the transition of hunter-gathering to agriculture, while attitudes toward meat production and animal killing have become increasingly characterized by moral ambiguity and disgust. To contribute to our understanding of the genesis of this meat parado...
During spontaneous meat fermentation, diverse microbial communities develop over time. These communities consist mainly of lactic acid bacteria (LAB) and coagulase-negative staphylococci (CNS), of which the species composition is influenced by the fermentation temperature and the level of acidification. Recent development and application of amplico...
Although refrigeration and modified-atmosphere packaging (MAP) allow for an extended shelf life of cooked charcuterie products, they are still susceptible to bacterial spoilage. To obtain better insights into factors that govern product deterioration, ample information is needed on the associated microbiota. In this study, sliced MAP cooked ham and...
Food labelling is a tool to inform consumers about the specifications and characteristics of a product. Additionally, labels display information about traditionality and naturalness, of which the meaning is highly subjective. There is a paucity of research examining attributes both of tradition and naturalness. In this study, traditionality was ass...
Eleven series of water kefir fermentation processes differing in the presence of oxygen and the type and concentration of inoculum and substrate, were followed as a function of time to quantify the impact of these parameters on the kinetics of this process via a modeling approach. Increasing concentrations of the water kefir grain inoculum increase...
Meat makes up a complex environment, home to an extensive bacterial diversity that is heavily influenced by environmental conditions during processing and storage. The current review focuses on the use of next-generation sequencing methods to unravel the complex microbial communities that are present in meat environments in greater detail. Recent a...
The bacterial communities that are established during natural meat fermentation depend on the processing conditions and the type of meat substrate used. Six pork samples of variable quality (reflected in pH values) and six less conventional meats (beef, horse, hare, wild deer, wild duck, and wild boar) were naturally fermented under controlled cond...
Insight into the microbial species diversity of fermented meats is not only paramount to gain control over quality development, but also to better understand the link with processing technology and geographical origin. To study the composition of the microbial communities, the use of culture-independent methods is increasingly popular but often sti...
The present debate outlined opposing views regarding the role of animal products in human diets. The YES position argues that the health benefits and safety of plant-based diets have been clearly established by consistent findings of randomized trials and observational studies; that animal products skew the diet toward saturated fat, excess protein...
Excessive attention to the animal versus plant binary food choice reflects society's moral views on eating right. To claim that avoidance of animal products is required to prevent chronic disease is not supported by evidence, makes little sense from an evolutionary perspective, and distracts policy makers from common-sense approaches to achieve ade...
The consumption of animal products exposes humans to saturated fat, cholesterol, lactose, estrogens, and pathogenic microorganisms, while displacing fiber, complex carbohydrates, antioxidants, and other components needed for health. In the process, consumption of animal products increases the risk for cardiovascular disease, cancer, diabetes, obesi...
Background: While predominant dietary guidelines promote foods low in fat and high in carbohydrates, evidence links high carbohydrate consumption to adverse health effects in populations that are metabolically challenged by (pre)diabetes or metabolic syndrome. An increasing number of people report eating diets that limit carbohydrates. These diets...
Acidification level and temperature modulate the beneficial consortia of lactic acid bacteria (LAB) and coagulase-negative staphylococci (CNS) during meat fermentation. Less is known about the impact of other factors, such as raw meat quality and salting. These could for instance affect the growth of the pathogen Staphylococcus aureus or of Enterob...
The production of ready-to-eat meat alternatives is currently on the rise, due to societal lifestyle trends, including flexitarianism, vegetarianism, and veganism. They usually consist of either processed meat substitutes that have been derived from plants or edible insects, depending on the market niche. Since the market relevance of such products...
Coagulase-negative staphylococci (CNS) make up a diverse bacterial group, appearing in a myriad of ecosystems. To unravel the composition of staphylococcal communities in these microbial ecosystems, a reliable species-level identification is crucial. The present study aimed to design a primer set for high-throughput amplicon sequencing, amplifying...
Cured cocoa beans are obtained through a post-harvest, batchwise process of fermentation and drying carried out on farms in the equatorial zone. Fermentation of cocoa pulp-bean mass is performed mainly in heaps or boxes. It is made possible by a succession of yeast, lactic acid bacteria (LAB), and acetic acid bacteria (AAB) activities. Yeasts ferme...
The virtues of ‘plant-based’ eating are commonly extolled in public and academic discourse, in particular in post-industrial countries and exceedingly so on a global level. Animal source foods, on the other hand, are regularly stigmatized for their alleged link with disease,environmental deterioration, and animal abuse. Although there is a reasonab...
Microbiological contamination of food during preparation and storage is a risk factor in institutional kitchens. In this Belgian study, hygiene practices in 40 institutional kitchens from four public sectors (10 hospitals, 10 schools, 10 retirement homes, and 10 child care centers) were evaluated to determine whether differences in these practices...
A total of 332 staphylococcal strains, mainly isolated from meat, were screened for antibacterial activity. Eighteen strains exhibited antibacterial activity towards species within the same genus. These antibacterial strains were further screened against Clostridium botulinum, to assess their potential as anticlostridial starter cultures for the de...
Meat is an important foodstuff, both from a nutritional and economic standpoint, available under a wide variety of raw and processed variants, including cooked, dry-cured, fermented, and smoked products. This chapter outlines the microbial diversity of meat and different meat products. Considerable microbial heterogeneity is found when comparing be...
European fermented meat products are prepared according to a wide variety of different recipes and processing conditions, which can influence their fermentative microbiota. However, due to the diverse processing conditions applied across Europe, it remained unclear to which degree bacterial heterogeneity can be encountered in commercially available...
Cooked poultry products are nutritious and economically valuable products that are at risk of bacterial spoilage, which can be postponed by cooling and modified-atmosphere-packaging (MAP). In this study, a cooked chicken product was stored at three different temperature ranges (4–6 °C, 7–9 °C, and 11–13 °C) and volatile production was measured over...
Cooked pork products, i.e., sliced cooked hams maintained under modified-atmosphere-packaging (MAP), were analysed both microbiologically and with respect to volatile levels during storage. Three storage temperature ranges were compared (4-6 °C, 7-9 °C, and 11-13 °C), representing different refrigeration conditions at household level. The microbial...
Despite its longstanding biosocial evolutionary background, the consumption of meat has nowadays become a controversial activity for a variety of reasons, being mostly related to anxieties about health, environmental impact, and animal welfare. The present chapter will outline the biosocial functions of meat within human communities, including the...
During spontaneous meat fermentations, Staphylococcus equorum, Staphylococcus saprophyticus, and Staphylococcus xylosus are generally the most prevailing species within the communities of coagulase-negative staphylococci (CNS). There is an interest to introduce CNS isolates from artisan-style spontaneous meat fermentations as starter cultures in mo...
Although equine meats and their derived smoked or fermented products are popular in some regions of the world, they only form a minor fraction of the global meat consumption. The latter may explain why their associated bacterial communities have not received much attention. In the present study, 69 different samples of equine meats and meat product...
Sliced cooked poultry products are susceptible to bacterial spoilage, notwithstanding their storage under modified-atmosphere packaging (MAP) in the cold chain. Although the prevailing bacterial communities are known to be mostly consisting of lactic acid bacteria (LAB), more information is needed about the potential variation in species diversity...
Consumption of rabbit meat traces back to the ancient civilizations that prospered around the Mediterranean. Due to their small size, rabbits have mostly been included in traditional meals for direct consumption, with little historical urgency to develop preservation methods. Therefore, rabbit-based dishes are widespread throughout Europe, but few...
Coagulase‐negative staphylococci (CNS) are ubiquitous microorganisms that are commonly present on animal skin and animal‐derived foods. They are members of the beneficial microbial consortia of several fermented food products where they contribute to quality. Currently, only a few CNS species are included in commercial starter cultures, although ma...
Coagulase-negative staphylococci (CNS) contribute to the product quality of fermented meats. In spontaneously fermented meats, CNS communities are variable and difficult to predict, as their compositions depend on a superposed combination of different processing factors. To partially disentangle this superposition, a meat model system was used to s...
Coagulase-negative staphylococci (CNS) are involved in colour and flavour formation of fermented meats. Their communities are established either spontaneously, as in some artisan-type products, or using a starter culture. The latter usually consists of Staphylococcus carnosus and/or Staphylococcus xylosus strains, although strains from other CNS sp...
Staphylococcus carnosus and Staphylococcus xylosus are commonly used, individually or in combination, within conventional starter cultures for the purposes of colour and flavour development during meat fermentation. Yet, little is known about the relative importance of both species under different processing conditions. The present study aimed at i...
The debate on meat's role in health and disease is a rowdy and dissonant one. This study uses the health section of the online version of The Daily Mail as a case study to carry out a quantitative and qualitative reflection on the related discourses in mass media during the first fifteen years of the 21st century. This period ranged from the fall-o...
In contemporary dietary advice, meat is depicted as a pharmakon: it is believed to either heal or poison the human body (and mind). Often, it also serves as a scapegoat for a wide range of public health issues and other societal problems. Related attitudes, practices, and beliefs pertain to a demarcated mode of thinking or episteme that is characte...
From a microbiological perspective, sourdough is to be considered as a specific and stressful ecosystem, harboring yeasts and lactic acid bacteria (LAB), that is used for the production of baked goods. With respect to the metabolic impact of the sourdough microbiota, acidification (LAB), flavor formation (LAB and yeasts), and leavening (yeasts and...
Coagulase-negative staphylococci (CNS) are not only part of the desirable microbiota of fermented meat products but also commonly inhabit skin and flesh wounds. Their proliferation depends on the versatility to use energy sources and the adaptation to fluctuating environmental parameters. In this study, the conversion of the amino acid arginine by...
Pork-based cooked products, such as cooked hams, are economically valuable foods that are vulnerable to bacterial spoilage, even when applying cooling and modified atmosphere packaging (MAP). Besides a common presence of Brochothrix thermosphacta, their microbiota are usually dominated by lactic acid bacteria (LAB). Yet, the exact LAB species diver...
Food-borne diseases, including those via dairy products, have been recognised as major threats to human health. The causes associated with dairy food-borne disease are the use of raw milk in the manufacture of dairy products, faulty processing conditions during the heat treatment of milk, post-processing contamination, failure in due diligence and...
Although meat fermentation originally emerged for preservation, fermented meats have evolved as a popular dietary compound because of their convenience and attractive sensory properties. After stuffing of the salted sausage batter into casings, a fermentation stage results from the activity of meat enzymes and microbial action by acidifying lactic...
The European Commission (EU) laid down the general principles and requirements of food law where it had changed the approach to food safety through the integrated control of the food chain. Hazard characterisation’ is the quantitative and/or qualitative evaluation of the adverse effects that may results from the ingestion of chemical, microbiologic...
In dry fermented sausages, myofibrillar proteins undergo intense proteolysis generating small peptides and free amino acids that play a role in flavour generation. This study aimed to identify small peptides arising from actin proteolysis, as influenced by the type of processing. Two acidification profiles were imposed, in order to mimic the pH nor...
The consumption of yogurt in Western countries has risen for over a century, first slowly, then more rapidly. The purpose of the present study was to investigate this prolonged phase of growth, by examining the popularity and the projected image of yogurt. A particular focus was on the way these aspects were reflected in consumption patterns and me...
Bifidobacteria are important members of the human gut microbiota. They are capable to degrade inulin‐type fructans (ITF; oligofructose and inulin) and arabinoxylan‐oligosaccharides (AXOS), non‐digestible polysaccharides (NDPs) present in the human diet. However, these properties are strain‐dependent, as they rely on the expression of the appropriat...
Together with acidifying lactic acid bacteria, yeasts play a key role in the production process of sourdough, where they are either naturally present or added as a starter culture. Worldwide, a diversity of yeast species is encountered, with Saccharomyces cerevisiae, Candida humilis, Kazachstania exigua, Pichia kudriavzevii, Wickerhamomyces anomalu...
With the increasing amount of evidence linking certain disorders of the human body to a disturbed gut microbiota, there is a growing interest for compounds that positively influence its composition and activity through diet. Besides the consumption of probiotics to stimulate favorable bacterial communities in the human gastrointestinal tract, prebi...
Inulin-type fructans (ITF) are known to cause a health-promoting bifidogenic effect, although the ITF degradation capacity of bifidobacteria in different intestinal regions remains unclear. The present study aims at offering new insights into this link, making use of a collection of 190 bifidobacterial strains, encompassing strains from gut biopsie...
The ability of the meat isolate Staphylococcus sciuri I20-1 to inhibit food-borne pathogens in view of its application as a functional starter culture for the production of clean-label fermented meats was investigated. The strain produced a heat-stable antibacterial compound of a proteinaceous nature that was released following primary metabolite p...
The capacity of strains to produce exopolysaccharides (EPS) is widespread among species of lactic acid bacteria and bifidobacteria, although the physiological role of these molecules is not yet clearly understood. When EPS are produced during food fermentation, they confer technological benefits on the fermented end products, such as improved textu...
The vulnerability of fish products to microbial damage can be partially countered by the use of bioprotective cultures. The latter are able to exert antimicrobial activity, often through the production of bacteriocins, so that spoilage microorganisms and/or pathogens are inhibited. Several food-compatible and effective strains have been selected, o...
Conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers are present in foods derived from ruminants as a result of the respective linoleic acid (LA) and α-linolenic acid (LNA) metabolism by ruminal microorganisms and in animals' tissues. CLA and CLNA have isomer-specific, health-promoting properties, including anti-carcinogenic,...
The ability of two coagulase-negative staphylococci (Staphylococcus sciuri I20-1 and Staphylococcus sciuri VT-S8-8) to inhibit food-borne pathogens in view of their application as functional starter cultures for the production of clean-label fermented meats was investigated. Both strains were active towards Clostridium botulinum and Staphylococcus...
The ability of different coagulase-negative staphylococci (CNS) to convert amino acids into technologically important metabolites was investigated in a rich medium (brain heart infusion, BHI) and in dry fermented sausages. Firstly, 56 CNS strains from five different species were tested for volatile and biogenic amine production after 24 h and 48 h...
The bacterial communities of a wide variety of chilled cooked meat products (29 different products), originating from pork and poultry, were subjected to extensive sampling. Samples were stored at 4 °C and analyzed at expiration date. Bacterial isolates were obtained from MRS agar, modified MRS agar, and M17 agar. Next, a procedure consisting of (G...
Cooked hams have gained an important position within the delicatessen market. Nowadays, consumers not only demand superior sensory properties but also request low levels of sodium and fat and the absence of conventional chemicals and preservatives used for the increase of the technological yield and shelf-life of the products. As a result, products...
Coagulase-negative staphylococci (CNS) are a major cause of intramammary infections (IMI) in dairy cows and they colonize the teat skin. Staphylococcus haemolyticus, one of the more common CNS, has been identified as a highly versatile opportunistic species. The aim of the present study was to gain better insight into the adaptation of S. haemolyti...
The ability of coagulase-negative staphylococci (CNS) to convert amino acids into volatile compounds and biogenic amines was investigated after 24 h and 48 h of incubation in a rich medium (brain heart infusion). Volatile compounds were measured with static-headspace gas chromatography and mass spectrometry (SH-GC-MS); biogenic amine measurements w...
The cured colour of European raw fermented meats is usually achieved by nitrate-into-nitrite reduction by coagulase-negative staphylococci (CNS), subsequently generating nitric oxide to form the relatively stable nitrosomyoglobin pigment. The present study aimed at comparing this classical curing procedure, based on nitrate reductase activity, with...
Since phenotypic methods to identify coagulase negative staphylococci (CNS) from the milk of ruminants often yield unreliable results, methods for molecular identification based on gene sequencing or fingerprinting techniques have been developed. In addition to culture-based detection of isolates, culture-independent methods may be of interest. On...
Within ecosystems that are poor in carbohydrates, alternative substrates such as arginine may be of importance to coagulase-negative staphylococci (CNS). Yet, the versatility of arginine conversion in CNS remains largely uncharted. Therefore, a set of 86 strains belonging to 17 CNS species was screened for arginine deiminase (ADI), arginase, and ni...
The performance of starter cultures during meat fermentation is a function of the combined actions of several process parameters. Not only are the recipe and the composition of the initial sausage batter of importance (i.e., the types and amounts of meat, fat, curing salt, spices, and other ingredients), but so too is the processing technology as s...