Impact of multiple hurdles on Listeria monocytogenes dispersion of survivors.

Pathogen exposure to multiple hurdles could result in variation in the number of survivors, which needs to be carefully considered using appropriate regression models for dealing with survivor dispersion. The aim of this study was to evaluate the impact of the hurdles on the random component of the measured variation and on its unexplained part (over or under-dispersion) representing the departure from randomness, i.e.

The COM-Poisson Process for Stochastic Modeling of Osmotic Inactivation Dynamics of .

Controlling harmful microorganisms, such as , can require reliable inactivation steps, including those providing conditions (e.g., using high salt content) in which the pathogen could be progressively inactivated.

An Italian web-based application for predictive microbiology to ensure food safety.

The use of predictive modelling tools, which mainly describe the response of microorganisms to a particular set of environmental conditions, may contribute to a better understanding of microbial behaviour in foods. In this paper, a tertiary model, in the form of a readily available and userfriendly web-based application (PP) is presented with research examples from our laboratories. Through the PP application, users have access to different modules, which apply a set of published models considered reliable for determining the compliance of a food product with EU safety criteria and for optimising processing throughout the identification of critical control points.

Survival strategies of Bacillus spores in food.

Control of bacterial spores is one of the major problem in the food preservation. Spores of Bacillus genus are commonly present in different environments, including soil and the gut of insects and animals and, as a result, they can be spread to all kind of foods. Due to their high resistance properties, their complete inactivation in food is often impossible without changing the product characteristics.

Involvement of alanine racemase in germination of Bacillus cereus spores lacking an intact exosporium.

The L-alanine mediated germination of food isolated Bacillus cereus DSA 1 spores, which lacked an intact exosporium, increased in the presence of D-cycloserine (DCS), which is an alanine racemase (Alr) inhibitor, reflecting the activity of the Alr enzyme, capable of converting L-alanine to the germination inhibitor D-alanine. Proteomic analysis of the alkaline extracts of the spore proteins, which include exosporium and coat proteins, confirmed that Alr was present in the B. cereus DSA 1 spores and matched to that encoded by B.

A simplified approach for modelling the bacterial growth/no growth boundary.

A simplified growth/no growth (G/NG) model, conceptually derived from the Gamma model and making direct and explicit use of growth limits of bacteria through a normalization constant (η), was proposed. The η value, which quantifies the product of the cardinal optimal distances for growth probability, is a species-independent constant. This is of importance when experimental data is missing or insufficient.

Changes of physicochemical, microbiological, and textural properties during ripening of Italian low-acid sausages. Proteolysis, sensory and volatile profiles.

In this study low-acid sausages were studied to characterize their physicochemical, microbiological, and textural properties during ripening. The final a(w) was 0.87-0.

Glassy state in Bacillus subtilis spores analyzed by differential scanning calorimetry.

Thermal properties of dried spores of Bacillus subtilis, investigated by differential scanning calorimetry (DSC), were studied. A reversible heat capacity shift ascribable to glass-rubber transition was observed at 90-115 degrees C. The transition was found to be a pressure-inhibited volume-activated event.

Growth of Listeria monocytogenes as influenced by viscosity and water activity.

The effects of osmotic stress on Listeria monocytogenes growth parameters was examined in relation to the viscosity of the growth media. In low-viscosity systems, growth of L. monocytogenes in glucose-supplemented media was comparable to growth in sucrose-supplemented media.

The Behavior of Yeast Populations in Stracchino Cheese Packaged under Various Conditions.

The growth of yeasts, lactic acid bacteria, pseudomonads, and enterobacteria during the refrigerated storage of an Italian soft cheese (Stracchino) in various packaging conditions (under air, under vacuum, and in the presence of ethanol) was studied. Yeasts were found to play a significant role in cheese spoilage, producing unplesant flavors and odors and causing significant reductions in the shelf life of the paper-wrapped cheeses. Packaging under vacuum decreased the yeast growth rates and reduced the populations attained at the end of the exponential phase of growth, resulting in a shelf-life extension of the Stracchino cheese of over 28 days.

Effect of Essential Oils on Aeromonas hydrophila in a Culture Medium and in Cooked Pork.

The inhibitory effects of essential oils of coriander, clove, nutmeg, and pepper towards Aeromonas hydrophila were studied in tryptic soy agar. Essential oils of clove, coriander, and nutmeg at concentrations of 500, 1,250, and 10,000 μg/ml, respectively, were effective in inhibiting the growth of A. hydrophila on tryptic soy agar.