Ochratoxin A (OTA) is one of the most important mycotoxins due to its prominent nephrotoxicity as well as potential carcinogenicity to human. OTA has been detected in a wide range of agricultural commodities including cereal grains and their processed products. OTA is stable under most food processing conditions while the reduction of OTA is more rapid and extensive under higher temperature and alkaline conditions. In this study, the effects of extrusion cooking on the stability of OTA in spiked (100 μg/kg) rice flour (moisture content, 16% wet weight basis) in the presence and absence of baking soda was investigated using a laboratory scale twin-screw extruder. The extrusion variables were temperature (120 and 150°C), screw speed (150, 200, and 250 rpm), and baking soda (0, 0.5, and 1%, w/w). Both unextruded and extruded samples were analyzed for OTA by high-performance liquid chromatography with a fluorescence detector (HPLC-FLD). The reduction of OTA was in the range of 78-82% with no added baking soda, whereas lesser reductions of 75-80% and 72-77% were observed at 0.5% and 1% baking soda, respectively. Both temperature and screw speed did not affect reduction of OTA during extrusion regardless of the presence or absence of baking soda. While the total color difference (ΔE) of extruded samples were increased with baking soda content, the radial expansion of extruded samples were decreased with baking soda content. These results suggest that OTA in rice flour may be reduced significantly by extrusion. In addition, added baking soda may negatively impact the reduction of OTA while its mechanism of action is unknown.

• Hyun Jung Lee(School of Food Science, University of Idaho)
• Dojin Ryu(School of Food Science, University of Idaho)