Selected Microbiological and Chemical Characteristics of Illegally Produced and Marketed Soft Hispanic-Style Cheeses in California

Abstract

Recently, there has been a great concern among California state health authorities and the dairy industry that large volumes of illegally produced Hispanic-style cheeses find their way into local markets. In cooperation with the State Milk and Dairy Foods Control Branch, California Department of Agriculture, 100 samples of soft Hispanic-style cheese were collected from all over the state by undercover agents during seizures by state authorities. The cheeses were analyzed in our laboratory for aerobic plate counts, the presence of Salmonella and Listeria, pH, moisture, and salt (%). The state laboratory tested for the presence of phosphatase. Salmonella was not detected in any of the samples. Two samples harbored LISTERIA monocytogenes and 2 more L. innocua. Geometric mean of APC on APT agar (Difco, Detroit, MI) was log10 8.64 (range 7.1–9.97) and on brain heart infusion (BHI) agar (Difco) was log10 8.81 (range 7.3–9.98). Fifty-six samples had a pH ≥ 6.0 with 13 samples ≥ 6.5. Forty percent of the samples had a brine of 4 to 8%. Thirty-one samples were phosphatase positive. The four Listeria positive samples had pH of 6.2, 6.2, 6.5, and 6.5 and brine of 4.15%, 4.29%, 3.93%, and 1.48%, respectively. All four samples were phosphatase positive. The high APC and the presence of Listeria spp. is a reflection of the overall unhygienic conditions prevailing during the processing and handling of these cheeses. They definitely present a serious threat to public health.