Native microflora in raw milk cheeses, including the Mexican variety Queso Chihuahua, contribute to flavor development through degradation of milk proteins. The effects of proteolysis were studied in four different brands of Mexican Queso Chihuahua made from raw milk. All of the cheeses were analyzed for chemical and sensory characteristics. Sensory testing revealed that the fresh cheeses elicited flavors of young, basic cheeses, with slight bitter notes. Analysis by gel electrophoresis and reverse phase-high performance liquid chromatography (RP-HPLC) revealed that the Queseria Blumen (X) and Queseria Super Fino (Z) cheeses show little protein degradation over time while the Queseria America (W) and Queseria Lago Grande (Y) samples are degraded extensively when aged at 4 °C for 8 weeks. Analysis of the mixture of water-soluble cheese proteins by mass spectrometry revealed the presence of short, hydrophobic peptides in quantities correlating with bitterness. All cheese samples contained enterococcal strains known to produce enterocins. The W and Y cheese samples had the highest number of bacteria and exhibited greater protein degradation than that observed for the X and Z cheeses.
Keywords: Cheese microbiology; Mass spectrometry; Protein profiling; Queso Chihuahua; RP-HPLC.