A novel method for analyzing grain facility heat treatment data*1

Abstract

Use of elevated temperatures (⩾50° C ) in food processing facilities for management of stored-product insects is a viable alternative to fumigation with methyl bromide. Effectiveness of heat treatment in controlling insects is determined by attainment of uniform temperatures between 50°C and 60°C. A unique surface area method was proposed and developed to assess the effectiveness of heat distribution. The pilot flour mill at Kansas State University, Manhattan, KS, was heated with natural gas (positive pressure) and electric (neutral pressure) heaters in June and August 1999, respectively. The proposed surface area method compared the two different heating systems and successfully quantified the under- and over-heated sections of the treated rooms at any given time during the treatments. A two-parameter nonlinear log-logistic equation was used to describe and predict the general trend in the floor surface area that is under 50°C as a function of treatment time, and percentage of floor surface area as a function of maximum floor temperature. With electric heating, time delays for temperature increase were considerably shorter than with gas heating. However, electric heating resulted in substantial amounts of under-heated floor areas ( T < 50°C) throughout the facility at the end of the heat treatment. The methods provided here, especially when coupled with the contour maps of temperature, can be used to design and evaluate heat treatment strategies in grain and food processing facilities.