Lactobacillus spp. from Mexican Cocido cheese were shown to produce bacteriocin-like substances (BLS) active against Staphylococcus aureus,Listeria innocua,Escherichia coli, andSalmonella typhimurium by using the disk diffusion method. Crude extracts of Lactobacillus fermentum showed strong inhibitory activity against Staph. aureus, L. innocua, E. coli, and Salmonella cholerae. Complete inactivation of antimicrobial activity was observed after treatment of crude extracts with proteinase K, pronase, papain, trypsin, and lysozyme, confirming their proteinaceous nature. However, antimicrobial activity was partly lost for some of the crude extracts when treated with α-amylase, indicating that carbohydrate moieties were involved. The antimicrobial activity of the crude extracts was stable at 65°C for 30min over a wide pH range (2-8), and addition of potassium chloride, sodium citrate, ethanol, and butanol did not affect antibacterial activity. However, antimicrobial activity was lost after heating at 121°C for 15min, addition of methanol or Tween 80. Fourteen out of 18 Lactobacillus spp. showed antimicrobial activity against different test microorganisms, and 12 presented bacteriocin-like substances. Generation time and growth rate parameters indicated that the antimicrobial activity of crude extracts from 3 different strains was effective against the 4 indicator microorganisms. One of the crude extracts showed inhibition not only against gram-positive but also against gram-negative bacteria. Bacteriocin-like substances produced by this specific Lactobacillus strain showed potential for application as a food biopreservative.

This study provides more information on one of the most popular artisanal cheeses with high cultural value and economic impact in northwestern Mexico. In view of the foregoing, good manufacturing practices need to be implemented for the manufacture of Cocido cheese. Also, it is of utmost importance to make sure that the heat treatment applied for cooking the curd ensures a phosphatase-negative test, otherwise it would be necessary to pasteurize milk. Nevertheless, since Cocido cheese is a non-ripened, high-moisture product, it is a highly perishable product that could present a health risk if not properly handled. © 2017 Society of Chemical Industry.

Poro de Tabasco cheese (PTC) is one of the most popular cheeses in southern Mexico. It has been made by traditional, nonstandardized artisanal techniques dating back more than 50 yr. These techniques result in the cheese having a heterogeneous chemical and microbiological composition and, consequently, distinct organoleptic characteristics. Scientific interest in artisanal cheese is growing because it represents a source of bacteria with potential health benefits. However, the quality of raw-milk cheeses often does not comply with official sanitary standards. The objective of the present study was to explore the chemical composition and microbiological quality of PTC and to describe its production process. Based on chemical composition, this cheese can be classified as a hard, full-fat, fresh cheese, with moisture on a fat-free basis and fat in dry matter ranging from 41 to 55% and from 49 to 57%, respectively. The chemical and microbiological composition of PTC varied among the evaluated dairies due to the lack of standardization in the production process. Microbial populations decreased during production, which may be associated with high acidity and high salt and low moisture contents, the presence of lactic acid bacteria or antimicrobial substances, and the drainage of whey. However, despite the absence of Escherichia coli, Salmonella spp., and Listeria monocytogenes in final cheeses for all dairies, Staphylococcus aureus and its toxins were found in some samples from one dairy. Therefore, heat treatment for milk and good manufacturing practices should be implemented throughout the entire production process to ensure a safe product.

No abstract

En la industria pecuaria es importante mantener al ganado en buen estado de salud para alcanzar niveles adecuados de producción. En la actualidad, el uso de antibióticos para el control de infecciones es limitado, debido a la resistencia de los microorganismos a estos fármacos. Por otro lado, los insecticidas y repelentes de origen sintéticos contienen químicos tóxicos para los animales, el humano y el medio ambiente. Una alternativa es utilizar compuestos químicos naturales derivados de plantas. El objetivo fue evaluar la actividad antimicrobiana, insecticida y repelente de extractos hidro-etanólicos de plantas. En este estudio, se utilizaron 12 extractos de plantas contra 5 diferentes bacterias y 8 especies de insectos. Los resultados mostraron que el extracto de Eucalyptus globulus y la mezcla de extractos presentaron actividad antimicrobiana contra Escherichia coli, Listeria monocytogenes, Salmonella typhimurium, Vibrio cholerae y Staphylococcus aureus (P<0.05). Por otro lado, los extractos de E. globulus y Azadirachta indica mostraron actividad insecticida contra todos los insectos (P<0.05); mientras que, la mezcla de los extractos mostró actividad repelente contra todos los insectos utilizados (P<0.05). Por lo anterior, los extractos hidro-etanólicos de plantas mostraron potencial para controlar bacterias patógenas e insectos indeseables en la industria pecuaria.