The 12 th ASEAN FOOD CONFERENCE 2011 16 -18 June, 2011 BITEC Bangna, Bangkok, Thailand  OD-263 Thermal Resistance of Local Isolates of Staphylococcus aureus Ratih Dewanti-Hariyadi 1,2,* , Juli Hadiyanto 2 and Eko Hari Purnomo 1,2 1 Southeast Asia Food Agricultural Science and Technology (SEAFAST) Center; 2 Department of Food Science and Technology, Faculty of Agricultural Technology, Bogor Agricultural University, Bogor 16002, Indonesia * Corresponding author: ratihde@ipb.ac.id Abstract Food poisoning is an important indicator for food safety status in any country. Report from The National Agency for Drugs and Food Control of Republic of Indonesia (BPOM) showed that 40.87% of food poisoning occurred in Indonesia was associated with homemade food. Staphylococcus aureus probably is an important pathogen contributing to the food poisoning cases in Indonesia, because this pathogen is a natural flora that lives in human body and could contaminate food due to poor sanitation and hygienic practices. Generally, growth of S. aureus can be prevented by temperature modification such us refrigeration and heating. Since most of Indonesian foods are heavily heated, it is interesting to know whether most processing could actually inactivate a large number of S. aureus and whether the pathogens isolated from local sources are tolerant to heat. This is important because the risk of having S. aureus surviving in cooked food is even worse since they could eventually produce enterotoxins. The goal of this research is to evaluate the heat resistance of several S. aureus isolated from ready to eat (RTE) Indonesian traditional foods. The study was conducted by inoculating 1 ml of a late log phased S. aureus culture into 9 ml of heating menstruum (Trypticase Soy Broth) at 52, 53, 54, and 56 o C for 5, 7, 10, and 15 minutes. S. aureus surviving from the heating process was enumerated on Baird Parker Agar (BPA) media containing egg yolk tellurite after incubation for 48 hours at 35 o C. Thermo tolerance parameters, i.e. D and Z values were estimated using standard regression analysis based on log linier models. The result was used to estimate the adequacy of various cooking methods for several RTE Indonesian traditional foods. The D 53 , D 54 , D 55 , and D 56 values of local isolates of S. aureus were 19.47- 64.59 min, 13.42 – 23.8 min, 6.59 – 14.3 min and 5.17-8.78 min, respectively. The thermal inactivation of S. aureus followed first order kinetics with r 2 values of 0.92-0.99. The Z values calculated in this study ranged from 3.37 to 6.06 o C. These values were within the range of reported Z values for most non-spore forming bacteria (4 – 6 o C). This study provided data on the thermal resistance of S. aureus isolated from Indonesia and validated that heating commonly applied in cooking of RTE traditional foods could reduce Staphylococcus aureus to up to 6.9x10 6 log cycle. However, common practices following heating of certain foods may allow recontamination, thus handling of RTE foods after cooking is very important for the management of this pathogen. Keywords: Staphylococcus aureus, D-value, Z-value, thermal resistance