DETERMINATION of RESIDENCE TIME DISTRIBUTION of NONSETTLING FOOD PARTICLES IN VISCOUS FOOD CARRIER FLUIDS USING HALL EFFECT SENSORS

Hall effect sensors were used to determine residence time distributions for diced carrot particles in 4% Colflo 67 carrier fluid. Four sensors at either end of a 3.2 m long 2 in. IDF tube viscometer allowed residence times to be measured for carrot particles incorporating a ceramic magnet. Mean particle residence times were greater than mean bulk residence time for 8 mm diced carrots, whereas 15 mm carrots showed trials in which particles travelled faster than the bulk fluid. Increasing concentration of 15 mm diced carrots from 3.25, 6.30, 9.16 to 11.85% w/w resulted in decreasing mean particle residence times from 17.6, 17.0, 15.9 to 14.3 s, with minimum residence times of 16.4, 16.2, 14.8 and 13.4 s, respectively. This sensing technique operates through stainless steel, providing applications for UHT foods containing particles. In addition, the technique was not affected by high particle concentration, and will operate for any distribution of particle size, shape or type.