Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/16/2006
Publication Date: 7/13/2006
Citation: Renye, J.A., Jr., Somkuti, G.A., Vallejo-Cordoba, B., Van Hekken, D.L. Gonzalez-Cordova, A.F. 2006 Characterization of the indigenous microflora present in commercial queso fresco from Mexico. (abstract) ADSA Annual Meeting. Paper No. T60. Journal of Dairy Science. 88(Suppl.l):180. Interpretive Summary: n/a
Technical Abstract: Queso Fresco is the most popular variety of Hispanic-style cheese consumed in the United States and Mexico. It is traditionally made from raw milk without specific starter cultures and the functional and flavor properties of the cheese are determined by the native microflora present in the raw milk. In the U.S., Queso Fresco is made from pasteurized milk with non-specific starter cultures resulting in a product with different organoleptic qualities from the traditional cheese. In this ARS-CIAD study, the indigenous microflora from six commercial Queso Fresco cheeses, obtained from Sonora, Mexico, were analyzed to identify bacterial species which may function as specific starter cultures. Four of the cheeses analyzed were made from raw milk and two from pasteurized milk. Classification of bacterial species was based on growth on selective media and 16S rDNA sequencing. The highest colony counts were obtained on M17 and MRS agar used for the selection of streptococci and lactobacilli respectively. Growth on MRS agar supplemented with vancomycin suggested that Leuconostoc species were present in all six samples. A high number of coliforms, enterococci and coagulase-positive staphylococci were identified in all raw milk samples. The number of enterococci remained high in cheese samples made from pasteurized milk but a 2 log10 reduction of coliforms was observed. Coagulase-positive staphylococci were reduced by 3 log10 in one pasteurized milk sample but remained high in the other (log 6.26 CFU/g). 16S rDNA sequence analysis revealed that lactobacilli were not present in any sample. Lactococcus lactis ssp. lactis was identified in four samples and Leuconostoc mesenteriodes and Entercoccus faecium were identified in all six samples. The results suggest that these species need further study to explore their potential as starter cultures for the production of cheese made from pasteurized milk while preserving the organoleptic qualities of traditional Queso Fresco.