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Title: Characterization of microflora in Mexican Chihuahua cheese

Author
item Renye, John
item Somkuti, George
item Van Hekken, Diane
item GUERRERO, PRIETO - CIAD,CUAUHTEMOC, MEXICO

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2011
Publication Date: 7/1/2011
Citation: Renye Jr, J.A., Somkuti, G.A., Van Hekken, D.L., Guerrero, P.V. 2011. Characterization of microflora in Mexican Chihuahua cheese. Journal of Dairy Science. 94:3311-3315.

Interpretive Summary: Queso Chihuahua, or Menonita, is a semi-hard Hispanic-style cheese produced predominantly in the northern Mexican state of Chihuahua. Queso Chihuahua is traditionally made using raw milk and usually consumed within 4 weeks of manufacture, thus not meeting the required 60-day holding period for raw milk cheeses sold in the U.S. The relatively short shelf life of raw milk Queso Chihuahua is the result of the cheese typically not aging well and developing an unacceptable texture. This style of cheese currently produced in the U.S. uses pasteurized milk and commercial starter bacteria but the properties of the cheese are believed to differ from the raw milk varieties. The bacteria present in the raw milk may contribute to the unique qualities found in traditional Queso Chihuahua, thus we have analyzed 10 commercial brands of Queso Chihuahua obtained from Mexico in order to identify the bacteria present in the final product. From the bacteria identified, it is thought that two species could serve as starter bacteria with an additional two to four species required for specific qualities such as flavor and texture of the final product. This study provides insight as to which bacteria should be considered when attempting to produce Queso Chihuahua-style cheese using pasteurized milk while trying to retain the traits associated with traditional raw milk cheeses.

Technical Abstract: This work was performed to identify the bacterial species present in 10 Chihauhua cheeses obtained from commercial producers in Mexico using 16S rRNA gene analysis. As expected some of the agar media initially used for isolation were not very selective, supporting the growth of a number of unrelated bacterial species. Sequence analysis identified potential pathogens, including Escherichia coli and Staphylococcus aureus, in all raw milk samples and two pasteurized milk samples. Streptococcus thermophilus and Lactococcus lactis ssp lactis were identified in 9 and 6 samples respectively and would serve as acidifying agents during cheese production. Lactobacilli were identified in all cheeses with the most prevalent being L. plantarum identified in 7 raw milk and 1 pasteurized milk cheeses. Leuconostoc mesenteroides and Streptococcus macedonicus were identified in 4 raw milk cheeses and both were present in all pasteurized milk samples suggesting they may play a role in the development of traditional Chihuahua cheese attributes.