Mathematical Modeling of Growth of \u3ci\u3eSalmonella\u3c/i\u3e in Raw Ground Beef under Isothermal Conditions from 10 to 45° C

The objective of this study was to develop primary and secondary models to describe the growth of Salmonella in raw ground beef. Primary and secondary models can be integrated into a dynamic model that can predict the microbial growth under varying environmental conditions. Growth data of Salmonella at nine different isothermal conditions — 10,15, 20, 25, 28, 32, 35, 42, and 45 °C were first fitted into primary models, namely the logistic, modified Gompertz, Baranyi, and Huang models. Performances of these models were evaluated by using various statistical criteria, namely mean square error (MSE), pseudo-R2, −2 log likelihood, Akaike\u27s and Bayesian\u27s information criteria. All the chosen models fitted well to the growth data of Salmonella based on these criteria. The results of statistical analysis showed that there was no significant difference in the performances of the four primary models, suggesting that the models were equally suitable for describing isothermal bacterial growth. The specific growth rates derived from each model was fitted to the Modified Ratkowsky equation, relating the specific growth rate to growth temperatures. It was also observed that the lag phase duration was an inverse function of specific growth rates. These models, if validated, can be used to construct dynamic models to predict potential Salmonella growth in raw ground beef

Inclusión dietaria de clinoptilolita como aditivo en la producción de rumiantes: Zeolita en producción de rumiantes

In recent years, research has focused on the study, development and validation of compounds of natural origin that can be used effectively and safely as an alternative to conventional growth promoters routinely used in livestock production, so that these do not compromise animal welfare, or the meat quality characteristics. One of these alternatives is the use of minerals such as zeolites of the clinoptilolite type. Clinoptilolite, when added to ruminant feed, has been shown to have beneficial effects on some parameters of ruminal fermentation, which translates into an improvement in the productive behavior of the animal. However, there is a lack of studies on ruminants, and in some cases have been inconclusive. Thus, the aim of this review is to discuss the effects of the dietary inclusion of clinoptilolite as a feed additive in ovines, and bovines supplemented with different levels of Clinoptilolite.En los últimos años, las investigaciones se han centrado en el estudio, desarrollo y validación de compuestos de origen natural que se puedan utilizar de manera eficaz y segura como alternativa a los promotores de crecimiento convencionales que se emplean rutinariamente en la producción pecuaria, de modo que estos no comprometan el bienestar animal, ni las características de calidad de la carne. Una de estas alternativas es el uso de minerales como las zeolitas de tipo clinoptilolita. La clinoptilolita al ser adicionada al alimento de rumiantes, ha demostrado tener efectos benéficos sobre algunos parámetros de la fermentación ruminal, lo cual se traduce en una mejora en el comportamiento productivo del animal. Los reportes sobre el uso en rumiantes son limitados y en algunos casos los resultados son inconsistentes. En esta revisión se discuten los efectos que se han encontrado en ovinos y bovinos al ser suplementados con distintas dosis de clinoptilolita

Inhibition of the CYP Enzymatic System Responsible of Heterocyclic Amines Bioactivation by an <i>Asclepias subulata</i> Extract

Asclepias subulata plant extract has previously demonstrated antiproliferative activity and antimutagenicity against heterocyclic aromatic amines (HAAs) commonly found in cooked meat. The objective of this work was to evaluate the in vitro ability of an ethanolic extract from the medicinal plant Asclepias subulata extract (ASE), non-heated and heated (180 °C), to inhibit the activity of CYP1A1 and CYP1A2, which are largely responsible for HAAs bioactivation. Ethoxyresorufin and methoxyresorufin O-dealkylation assays were performed in rat liver microsomes exposed to ASE (0.002–960 µg/mL). ASE exerted an inhibitory effect in a dose-dependent manner. The half inhibitory concentration (IC50) for unheated ASE was 353.6 µg/mL and 75.9 µg/mL for heated ASE in EROD assay. An IC40 value of 288.4 ± 5.8 µg/mL was calculated for non-heated ASE in MROD assay. However, after heat treatment, the IC50 value was 232.1 ± 7.4 µg/mL. Molecular docking of corotoxigenin-3-O-glucopyranoside, one of the main components of ASE, with CYP1A1/2 structure, was performed. Results show that the interaction of corotoxigenin-3-O-glucopyranoside with CYP1A1/2s’ α-helices, which are related with the active site and the heme cofactor, may explain the plant extract’s inhibitory properties. Results showed that ASE inhibits CYP1A enzymatic subfamily and may potentially act as a chemopreventive agent by inhibiting bioactivation of promutagenic dietary HAAs

Antagonistic Activity of Bacteriocin-like Inhibitory Substances from <i>Enterococcus lactis</i> Isolated from the Surface of Jalapeno Pepper against Foodborne Pathogens

Lactic acid bacteria (LAB) can produce peptides known as bacteriocins with antagonistic activity against foodborne pathogens. The potential of LAB isolated from the surface of jalapeno peppers to produce bacteriocins with antagonistic activity against Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella Typhimurium was evaluated. Previously isolated LAB strains were reactivated, and their cell-free supernatants (CFSs) were evaluated. Out of 390 reactivated strains, 60 produced bacteriocin-like inhibitory substances (BLIS) since their antagonistic activity was lost after proteases addition. Subsequently, 16 BLIS showed heat resistance (HR-BLIS), retaining their bioactivity after heat treatment (121 °C for 15 min). By 16S rRNA gene sequencing and antibiotic susceptibility tests, LAB strains producing HR-BLIS were identified as Enterococcus lactis. Four HR-BLIS exhibited a minimum inhibitory concentration (MIC) of 80 mg/mL against L. monocytogenes. MIC and minimum bactericidal concentration (MBC) of HR-BLIS-67 for S. aureus (MIC = 80 mg/mL; MBC = 320 mg/mL), S. Typhimurium (MIC = 150 mg/mL; MBC = 250 mg/mL), and E. coli O157:H7 (MIC = 250 mg/mL; MBC = 400 mg/mL) were determined. LAB isolated from the surface of jalapeno pepper produced HR-BLIS (possibly enterocin) that exhibited broad-spectrum antagonistic activity against foodborne pathogens; therefore, they are a promising source of natural antimicrobials to ensure food safety