Microbiological Profile of Two Artisanal Mexican Cheeses During Manufacturing Process

Introduction: Artisanal Mexican cheeses generally are made by farmers on a small scale using traditional techniques and in some occasions raw milk. The sensorial characteristics are unique, however the final quality of the product, including safety, is variable and could represent a health risk to the consumer.

Purpose: The objective of the present study was to study the evolution of the microflora during the processing of two Mexican artisanal cheeses (“bola” and “poro”) produced during dry and rainy seasons.

Methods: Along the manufacturing process, samples of bola and poro cheese were analyzed to quantify the levels of aerobic plate count (APC), lactic acid bacteria (LAB), yeast, molds, coliforms, and Escherichia coli. The presence of Listeria monocytogenes, Staphylococcus aureus and Salmonella spp. were also determined.

Results: A total of 107 and 143 samples of bola and poro cheese were analyzed.  In bola cheese along the ripening (50, 80, and 110 days) populations of all microbial groups decreased; the levels of APC, LAB, yeasts and molds ranged from 7.2 to 5.6, 7.6 to 6.0, 3.9 to 1.4 and 4.5 to 3.6 log CFU/g, respectively. In poro cheese after 7, 30 and 60 days of storage, populations of APC, LAB, yeast and molds ranged from 6.1 to 5.8, 6.2 to 5.9, 4.0 to 3.4 and 4.4 to 4.2 log CFU/g, respectively. In general in both type of cheeses produced during rainy season, the levels of all indicator microorganism were higher. In all samples coliforms and E. coli were under detection limit (<3 MPN/g), whereas L. monocytogenes, S. aureus and Salmonella were not isolated from any sample. 

Significance: These results showed that microbial quality of artisanal cheeses is acceptable. However, if the manufacturing method is not standardized the risk for the consumer still is present.