Title: Viability loss of Escherichia coli cell populations in whey and corn meal snack treated at different temperatures with a twin screw extruder Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 7, 2011
Publication Date: June 11, 2011
Citation: Ukuku, D.O. 2011. Viability loss of Escherichia coli cell populations in whey and corn meal snack treated at different temperatures with a twin screw extruder. IFT Annual meeting and Food Expo, June 11-14, 2011, New Orleans, LA., Volume 1, P. 1. Technical Abstract: Many studies on the development of new and/ or value added nutritional meals for the US consumer have been reported. However, information on the effect of treatment parameters on microbial safety of foods extruded below 100 deg C is limited. In this study, we investigated the effect of extrusion treatment at different temperatures on viability loss of E. coli cell populations inoculated on corn and whey protein isolates. Extrusion treatment temperatures were set at 35 deg C, 55 deg C, 75 deg C, and 95 deg C and two materials, corn and whey protein products were conveyed separately into the extruder with a series 6300 digital feeder, type T-35 twin screw volumetric feeder (K-Tron Corp., Pitman, NJ) at a set speed of 600 rpm, and E. coli water solution (109 CFU/ml) was added into the extruder at the rate of 1.0 L/h with an electromagnetic dosing pump (Milton Roy, Acton, MA). The initial bacterial population averaged 8.8 log10 CFU/g on corn and whey protein. Extrusion treatment at 35 and 55 deg C led to 7 log reduction of E. coli populations in corn product. Extrusion treatments at 75 deg C and above led to below detection (<10 CFU/g) of E. coli cell populations in corn product. Population reductions of E. coli cells in whey samples similarly treated was significantly different. Only 1.8 and 4.4 log reductions were achieved at 35 deg C, and 55 deg C, respectively. And treatment at 75 deg C led to 5.8 log reduction while surviving cell populations were below detection (<10 CFU/ml) at 95 deg C. The results of this study suggest higher extrusion treatment temperature at 95 deg C or above to achieve microbial safe extruded whey product and >75 deg C treatment for corn product.