D VALUES OF COMPOSITE SALMONELLA ENTERICA SEROTYPES TYPHIMURIUM AND ENTERITIDIS IN PHILIPPINE NATIVE ORANGE JUICE ALONZO A. GABRIEL 1 Department of Food Science and Nutrition College of Home Economics University of the Philippines Diliman, Quezon City, Philippines Accepted for Publication May 8, 2007 ABSTRACT This study established the decimal reduction times (D values) of a com- posite inoculum of Salmonella enterica serotypes Typhimurium (American Type Culture Collection 13311 and E 1366) and Enteritidis (BIOTECH 1963) in Philippine native orange juice (pH 3.0, 0.84 % citric acid, 8.4°Brix). Acid- adapted cells (10 log 10 cfu/g) were heated to 50–70C for 0–1.5 min and re- covered by surface plating onto a selective (bismuth sulfite agar) and a nonselective medium (nutrient agar [NA]). Results showed that in both enu- merating media and in all heating temperatures, survivor populations signifi- cantly decreased (P < 0.05) with increasing treatment time. The greater populations enumerated on NA in all treatment times were attributed to the sublethal injuries imparted by the acidity of the suspending medium and the heat treatments. The D values calculated from the survivor populations on both media were not significantly different (P > 0.05). The D values ranged from 0.16 to 0.40 min. PRACTICAL APPLICATIONS This study established the thermal inactivation rates of a composite Sal- monella spp. inoculum in a Philippine orange juice medium. Salmonella is a target organism pertinent in the assuring citrus juices. Hence, appropriate thermal process schedules for citrus juices with similar physicochemical prop- erties as the test medium, against the test organisms may be calculated using the results obtained from this study. 1 Corresponding author. A.A. Gabriel, Alonso Hall, Regidor Street, University of the Philippines, Diliman Campus, 1101 Quezon City, Philippines. TEL: +632-9818500 local 3407; TEL/FAX: +632- 9202091, +632-9273828; EMAIL: alonzo.gabriel@up.edu.ph Journal of Food Processing and Preservation 31 (2007) 649–658. All Rights Reserved. © 2007, The Author(s) Journal compilation © 2007, Blackwell Publishing 649