Open Access
Influence of acid adaptation on the probability of germination of Clostridium sporogenes spores against pH, NaCl and time
(MDPI, 2020) Valero, Antonio; Olagüe Ramos, Elena; Medina Pradas, Eduardo; Garrido Fernández, Antonio; Romero Gil, Verónica; Cantalejo Díez, María Jesús; García Gimeno, Rosa María; Pérez Rodríguez, Fernando; Posada Izquierdo, Guiomar Denisse; Arroyo López, Francisco Noé; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura
The Clostridium sp. is a large group of spore-forming, facultative or strictly anaerobic, Gram-positive bacteria that can produce food poisoning. The table olive industry is demanding alternative formulations to respond to market demand for the reduction of acidity and salt contents in final products. while maintaining the appearance of freshness of fruits. In this work, logistic regression models for non-adapted and acid-adapted Clostridium sp. strains were developed in laboratory medium to study the influence of pH, NaCl (%) and time on the probability of germination of their spores. A Clostridium sporogenes cocktail was not able to germinate at pH <5.0, although the adaptation of the strains produced an increase in the probability of germination at 5.0-5.5 pH levels and 6% NaCl concentration. At acidic pH values (5.0), the adapted strains germinated after 10 days of incubation, while those which were non-adapted required 15 days. At pH 5.75 and with 4% NaCl, germination of the adapted strains took place before 7 days, while several replicates of the non-adapted strains did not germinate after 42 days of storage. The model was validated in natural green olive brines with good results (>81.7% correct prediction cases). The information will be useful for the industry and administration to assess the safety risk in the formulation of new processing conditions in table olives and other fermented vegetables.
Open Access
Prevalence, identification and antimicrobial resistance of Listeria monocytogenes and Listeria spp. isolated from poultry and pork meat
(Wiley, 2024) Martínez-Laorden, Alba; Arraiz-Fernández, Celia; Cantalejo Díez, María Jesús; González-Fandos, Elena; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD
The aim of this work was to evaluate the prevalence of Listeria monocytogenes and other Listeria spp. in chicken, duck, quail, turkey and pork meat, including the antibiotic resistance of isolated strains. A total of 184 meat samples were collected from different retailers in La Rioja (Spain). The presence of Listeria spp. and L. monocytogenes were detected in 24.46% and 10.32% of the meat samples respectively. L. monocytogenes was the predominant Listeria spp. found in chicken, quail and pork meat, while L. innocua and L. welshimeri were the predominant species in duck and turkey meat respectively. A total of thirty-three strains (55.93%) of Listeria spp. were found to be multi-resistant (resistant to ≥3 families of antibiotics). The highest multi-resistant rates were observed in L. monocytogenes (73.68%) and L. innocua (70.59%), followed by L. ivanovii (50%). Resistance to ampicillin and trimethoprim-sulfamethoxazole were found in L. monocytogenes strains isolated from chicken, being of special concern, since these antibiotics are used in the treatment of listeriosis. Special measures should be taken to reduce meat contamination such as adequate handling, correct preparation (cooking) and cleaning and disinfection in order to avoid cross-contamination.
Open Access
Modeling the growth of six Listeria monocytogenes strains in smoked salmon pâté
(MDPI, 2023) Bolívar, Araceli; Garrote Achou, Chajira Camila; Tarlak, Fatih; Cantalejo Díez, María Jesús; Correia Peres Costa, Jean Carlos; Pérez Rodríguez, Fernando; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura
In this study, the growth of six L. monocytogenes strains isolated from different fish products was quantified and modeled in smoked salmon pâté at a temperature ranging from 2 to 20 °C. The experimental data obtained for each strain was fitted to the primary growth model of Baranyi and Roberts to estimate the following kinetic parameters: lag phase (λ), maximum specific growth rate (μmax), and maximum cell density (Nmax). Then, the effect of storage temperature on the obtained μmax values was modeled by the Ratkowsky secondary model. In general, the six L. monocytogenes strains showed rapid growth in salmon pâté at all storage temperatures, with a relatively short lag phase λ, even at 2 °C. The growth behavior among the tested strains was similar at the same storage temperature, although significant differences were found for the parameters λ and μmax. Besides, the growth variations among the strains did not follow a regular pattern. The estimated secondary model parameter Tmin ranged from −4.25 to −3.19 °C. This study provides accurate predictive models for the growth of L. monocytogenes in fish pâtés that can be used in shelf life and microbial risk assessment studies. In addition, the models generated in this work can be implemented in predictive modeling tools and repositories that can be reliably and easily used by the fish industry and end-users to establish measures aimed at controlling the growth of L. monocytogenes in fish-based pâtés.

Cantalejo Díez, María Jesús

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