Microbiological Changes during Ripening of Chihuahua Cheese Manufactured with Raw Milk and Its Seasonal Variations

Chihuahua cheese is a traditional cheese produced in Northwest Mexico that is consumed shortly after production. Cheeses prepared during autumn, winter and summer were collected from five dairies, and analyzed to determine seasonal influence on proximate analysis, texture profile and the microbiological dynamic during a ripening period of 270 days. Coliforms, coagulase-positive staphylococci, molds, yeast, as well as presumptive mesophilic lactobacilli, thermophilic lactobacilli, lactococci, thermophilic cocci and enterococci, were enumerated by plate count on selective agar. Manufacturing dairy had an effect on Chihuahua cheese composition and texture profile. Seasonality influence on the microbial dynamic was observed, since the highest initial counts of coliforms (5.14 log CFU/g), coagulase-positive staphylococci (4.13 log CFU/g) and mesophilic lactobacilli (7.86 log CFU/g) were detected on summer samples. Also, ripening time affected the survival of coliforms and presumptive lactococci after 270 days (1.24 and 5.89 log CFU/g respectively) while from day 90th, coagulase-positive staphylococci were absent. Microbial changes and seasonal influence provide information on the microbiota that can influence the sensorial characteristics of Chihuahua cheese.

Microbial Dynamic Changes under Different Grazing Intensities in Growing Seasons of Desert Steppe

Soil microbial plays a very important role in the grassland ecosystems, but measured data is very lack. In this paper, based on the ground survey data microbial dynamic changes in growing seasons of Desert steppe in 2012 was estimated. The main conclusions are as follows: soil bacteria number began to increase in May, reached to highest value in July and then began to decrease. Actinomycetes population increased first and then decreased. Fungus amount decreased in beginning and then increased. Grazing significantly affect the number of soil microbial, shown as soil microbial of very severe grazing fences are significantly lower than other fences.