Dike O. Ukuku, Charles Onwulata and Sudarsan Mukhopadhyay
New studies on the development of low-temperature extruded value-added nutritional foods containing corn meal and whey protein isolate have been reported. However, information on the effect of extrusion treatment parameters on microbial safety of foods below 100°C is limited. In this study, we investigated the effect of extrusion treatments at 35°C, 55°C, 75°C, and 95°C on reduction of E. coli cell populations inoculated onto corn meal (CM) and whey protein concentrate (WPC80) at 8.8 log 10 CFU/g. Inactivation of E. coli bacteria on CM and WPC80 extruded at 35 and 55°C averaged 4.8 log, 6.9 log and 1.8 log, 4.3 log, respectively. Extrusion treatment at 75°C and above reduced E. coli (ATCC-25922) cells on CM to below detection (<20 CFU/g); but treatment at 95°C was needed to achieve a similar below detection (<20 CFU/g) for WPC80. The results of this study suggest that corn meal products extruded at 75°C or above, and whey protein isolate extruded at 95°C, will enhance the microbiological safety of the extrudates.