Journal of Food Processing & Technology

Abstract

Behavior of Escherichia coli Bacteria in Whey Protein Concentrate and Corn Meal during Twin Screw Extrusion Processing at different Temperatures

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.