Intra- and inter-batch variability in raw pork challenge test studies and their consequences on model predictions: An intricate interplay between L. monocytogenes, the microbiome, and packaging atmosphere.

The purpose of this study was to conduct challenge studies in raw pork by strictly following all aspects of the 2014 EURL technical guidance document for conducting shelf-life studies on Listeria monocytogenes. Growth potential was assessed on three batches of self-cut pork chops and one batch of in-house prepared pure minced pork without any additives in air and MAP (70 % O/30% CO) packaging. Pork chops did not support the growth of the pathogen throughout the shelf-life, given the specific conditions used in this study, with growth potential values of 0.

Time Is of the Essence-Early Activation of the Mevalonate Pathway in Apple Challenged With Gray Mold Correlates With Reduced Susceptibility During Postharvest Storage.

Apple is typically stored under low temperature and controlled atmospheric conditions to ensure a year round supply of high quality fruit for the consumer. During storage, losses in quality and quantity occur due to spoilage by postharvest pathogens. One important postharvest pathogen of apple is .

Why mass allocation with representative allocation factor is preferential in LCA when using residual livestock products as organic fertilizers.

The production impact of agricultural residues are generally not accounted for in LCAs when they are given a second life as feedstocks for bio-fuels/plastics/fertilizers. Such is the case for the organic fertilizers manure and blood meal (stemming from livestock) used in organic cultivation. This raises questions on how realistic comparisons are between conventional cultivation systems and organic systems: the flows of resources and associated impacts are not represented equivalently in both systems.

Identifying Belgian protein consumption typologies by means of clustering and classification to move towards personalized advices for sustainable and nutritious food choices.

Protein sources are determinant for the environmental impact and nutritiousness of our food consumption patterns. Dietary advices, in terms of nutritional values and, more recently, the associated environmental impacts, are mostly formulated at nationwide level. However, actual food consumption patterns are variable between individuals within nations, leading to a need for more personalized dietary advices to ensure the feasibility of potential dietary changes.

Genetic Types in the Pork Processing Plant Environment: From Occasional Introduction to Plausible Persistence in Harborage Sites.

The purpose of this study was to investigate the occurrence and genetic diversity in three Belgian pork cutting plants. We specifically aim to identify harborage sites and niche locations where this pathogen might occur. A total of 868 samples were taken from a large diversity of food and non-food contact surfaces after cleaning and disinfection (C&D) and during processing.

Study of the transfer of Listeria monocytogenes during the slaughter of cattle using molecular typing.

The introduction, transmission, and persistence of Listeria monocytogenes in Belgian beef slaughterhouses was investigated using genetic characterization. During slaughter, samples were taken of the hide, carcass, and environment to detect the pathogen. Remarkably, L.

Modelling postmortem evolution of pH in beef M. under two different cooling regimes.

A model based on enzyme kinetics was developed to predict differences in postmortem pH change in beef muscles as affected by cooling rate. For the calibration and validation of the model, pH and temperature measurements were conducted at different positions in following conventional carcass cooling or faster cooling of the muscle after hot boning. The glycogen conversion, and, hence, the pH fall, was observed to significantly vary with position and cooling regime but only during the initial hours of cooling.

To disinfect or not to disinfect in postharvest research on the fungal decay of apple?

Postharvest losses of fruit and vegetables can reach up to 30%, the main cause being microbial decay. For apple fruit, mostly fungal pathogens, such as Penicillium expansum, Colletotrichum spp., Neofabraea spp.

Dynamic Labeling Reveals Temporal Changes in Carbon Re-Allocation within the Central Metabolism of Developing Apple Fruit.

In recent years, the application of isotopically labeled substrates has received extensive attention in plant physiology. Measuring the propagation of the label through metabolic networks may provide information on carbon allocation in sink fruit during fruit development. In this research, gas chromatography coupled to mass spectrometry based metabolite profiling was used to characterize the changing metabolic pool sizes in developing apple fruit at five growth stages (30, 58, 93, 121, and 149 days after full bloom) using C-isotope feeding experiments on hypanthium tissue discs.

Kinetic modelling: an integrated approach to analyze enzyme activity assays.

Background: In general, enzyme activity is estimated from spectrophotometric data, by taking the slope of the linear part of the progress curve describing the rate of change in the substrate or product monitored. As long as the substrate concentrations are sufficiently high to saturate the enzyme and, the velocity of the catalyzed reaction is directly proportional to the enzyme concentration. Under these premises, this velocity can be taken as a measure of the amount of active enzyme present.

Thermal inactivation kinetics of surface contaminating Listeria monocytogenes on vacuum-packaged agar surface and ready-to-eat sliced ham and sausage.

The aim of this work was to study thermal inactivation kinetics of Listeria monocytogenes on vacuum-packaged food surfaces. The kinetics were first determined on model agar systems (BHI agar plates), mimicking cooked meat products, which have the same characteristics (pH, sodium chloride (NaCl) or sodium lactate (NaL) content and thickness) as the cooked meat products. Then, in order to validate how well the thermal inactivation on the model agar system simulated inactivation on real products, inactivation kinetics of L.

A mechanistic modelling approach to understand 1-MCP inhibition of ethylene action and quality changes during ripening of apples.

Background: 1-Methylcyclopropene (1-MCP) inhibits ripening in climacteric fruit by blocking ethylene receptors, preventing ethylene from binding and eliciting its action. The objective of the current study was to use mathematical models to describe 1-MCP inhibition of apple fruit ripening, and to provide a tool for predicting ethylene production, and two important quality indicators of apple fruit, firmness and background colour.

Results: A model consisting of coupled differential equations describing 1-MCP inhibition of apple ripening was developed.

Thermal inactivation and sublethal injury kinetics of Salmonella enterica and Listeria monocytogenes in broth versus agar surface.

The objective of the present study was to compare the thermal inactivation and sublethal injury kinetics of Salmonella enterica and Listeria monocytogenes in broth (suspended cells) and on solid surface (agar-seeded cells). A 3-strain cocktail of S. enterica or L.

Cross-protection between controlled acid-adaptation and thermal inactivation for 48 Escherichia coli strains.

Given the importance of pH reduction and thermal treatment in food processing and food preservation strategies, the cross-protection between acid adaptation and subsequent thermal inactivation for 48 Escherichia coli strains was investigated. Those strains were selected among 188 E. coli strains according to their odds of growth under low pH conditions as determined by Haberbeck et al.

Slow softening of Kanzi apples (Malus×domestica L.) is associated with preservation of pectin integrity in middle lamella.

Kanzi is a recently developed apple cultivar that has an extremely low ethylene production, and maintains its crispiness during ripening. To identify key determinants of the slow softening behaviour of Kanzi apples, a comparative analysis of pectin biochemistry and tissue fracture pattern during different ripening stages of Kanzi apples was performed against Golden Delicious, a rapid softening cultivar. While substantial pectin depolymerisation and solubilisation was observed during softening in Golden Delicious apples, no depolymerisation or increased solubilisation was observed in Kanzi apples.

Growth and inactivation of Salmonella enterica and Listeria monocytogenes in broth and validation in ground pork meat during simulated home storage abusive temperature and home pan-frying.

Ground pork meat with natural microbiota and inoculated with low initial densities (1-10 or 10-100 CFU/g) of Salmonella enterica or Listeria monocytogenes was stored under abusive temperature at 10°C and thermally treated by a simulated home pan-frying procedure. The growth and inactivation characteristics were also evaluated in broth. In ground pork meat, the population of S.

Multi-objective experimental design for (13)C-based metabolic flux analysis.

(13)C-based metabolic flux analysis is an excellent technique to resolve fluxes in the central carbon metabolism but costs can be significant when using specialized tracers. This work presents a framework for cost-effective design of (13)C-tracer experiments, illustrated on two different networks. Linear and non-linear optimal input mixtures are computed for networks for Streptomyces lividans and a carcinoma cell line.

Metabolic profiling reveals ethylene mediated metabolic changes and a coordinated adaptive mechanism of 'Jonagold' apple to low oxygen stress.

Apples are predominantly stored in controlled atmosphere (CA) storage to delay ripening and prolong their storage life. Profiling the dynamics of metabolic changes during ripening and CA storage is vital for understanding the governing molecular mechanism. In this study, the dynamics of the primary metabolism of 'Jonagold' apples during ripening in regular air (RA) storage and initiation of CA storage was profiled.

Effectiveness of inactivation of foodborne pathogens during simulated home pan frying of steak, hamburger or meat strips.

In order to evaluate the effect of simulated home pan frying of raw meat and meat preparations of different animal species on the thermal inactivation of pathogens, the heat resistance (D-value) of three strains of Campylobacter jejuni, Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes and two strains of generic E. coli was validated in BHI and adjusted BHI (i.

Formate hydrogen lyase mediates stationary-phase deacidification and increases survival during sugar fermentation in acetoin-producing enterobacteria.

Two fermentation types exist in the Enterobacteriaceae family. Mixed-acid fermenters produce substantial amounts of lactate, formate, acetate, and succinate, resulting in lethal medium acidification. On the other hand, 2,3-butanediol fermenters switch to the production of the neutral compounds acetoin and 2,3-butanediol and even deacidify the environment after an initial acidification phase, thereby avoiding cell death.

Multi-response optimization of the extraction and derivatization protocol of selected polar metabolites from apple fruit tissue for GC-MS analysis.

Given the complexity of the plant metabolome exhibiting a wide spectrum of physico-chemical properties, finding the best compromise for GC-MS analysis is a challenging exercise. In this study, the GC-MS protocol for extracting and analyzing polar metabolites from apple tissue is optimized. We found pure methanol extraction to be slightly better as compared to the two phase methanol/chloroform/water extraction in terms of introducing less degradation of the extracted metabolites while being comparable in extraction efficiency and repeatability.

Pectin modifications and the role of pectin-degrading enzymes during postharvest softening of Jonagold apples.

This study aimed at understanding softening in Jonagold apple (Malus×domestica Borkh.) fruits, by investigating pectin modifications and the evolution of pectin-modifying enzymes during postharvest storage and ripening. Jonagold apples were harvested at commercial maturity and stored at different temperatures and controlled atmosphere conditions for 6 months, followed by exposure to ambient shelf life conditions (20 °C under air) for 2 weeks.

Modeling the fate of Escherichia coli O157:H7 and Salmonella enterica in the agricultural environment: current perspective.

The significance of fresh vegetable consumption on human nutrition and health is well recognized. Human infections with Escherichia coli O157:H7 and Salmonella enterica linked to fresh vegetable consumption have become a serious public health problem inflicting a heavy economic burden. The use of contaminated livestock wastes such as manure and manure slurry in crop production is believed to be one of the principal routes of fresh vegetable contamination with E.

2,3-Butanediol fermentation promotes growth of Serratia plymuthica at low pH but not survival of extreme acid challenge.

The mechanisms by which Enterobacteriaceae can survive or grow at low pH are of interest because members of this family are increasingly linked to problems of spoilage and foodborne infection related to mildly acidic foods. In this work, we investigated the contribution of the 2,3-butanediol fermentation pathway in coping with specific forms of acid stress in Serratia plymuthica RVH1. This pathway consumes intracellular protons, similar to the amino acid decarboxylases which are involved in acid resistance in Enterobacteriaceae.

A transcriptomics-based kinetic model for ethylene biosynthesis in tomato (Solanum lycopersicum) fruit: development, validation and exploration of novel regulatory mechanisms.

The gaseous plant hormone ethylene is involved in many physiological processes including climacteric fruit ripening, in which it is a key determinant of fruit quality. A detailed model that describes ethylene biochemistry dynamics is missing. Often, kinetic modeling is used to describe metabolic networks or signaling cascades, mostly ignoring the link with transcriptomic data.