11-4 |
Laboratory exercise demonstrating three types of heat penetration in canned foods |
J. H. GOFF1, C. O'Bryan1, P. G. Crandall1, and W. G. McGlynn2. (1) Dept. of Food Science, Univ. of Arkansas, 2650 N. Young Ave., Fayetteville, AR 72704, (2) Oklahoma State Univ., Oklahoma Food & Agricultural Products Research & Technology Center, Rm. 112, Stillwater, OK 74078-6055 In 1998 over 24 billion cans of food were produced in the U.S. Food Science graduates hired by canning companies are expected to be familiar with the penetration of heat into canned foods. Students must understand the differences among convection, conduction and broken line heating in canned foods. The hands-on approach is the most effective method to teach these concepts. Our objective is to provide examples of these heat penetration characteristics which will increase student knowledge of all types of heating and cooling of foods. A vertical still retort and an FMC Steritort were used to process 300 X 407 cans of garbanzo beans and raw and pregelatinized cracked wheat. Wheat was gelatinized by heating in water to 100 °C, canned and cooled to < 4 °C. Ice water covered the beans and raw wheat. Heat penetration data were recorded with TechniCal CalSoft using Ecklund-Harrison thermocouples. Thermocouples for beans in the still retort were centered at the cold spot, 3.8 cm from the bottom of the can. Other thermocouples were placed in the geometric center of cans. All Steritort cans were equipped with Ecklund-Harrison rotary contactors. Both retorts were operated at 121 °C for 20 min. The Steritort was operated at 5 rpm. Garbanzo beans showed pure convection heating with slopes of 22.5 for still and 24.7 for rotary processing. Raw cracked wheat and water produced convection slopes of 15.9 for still and 16.3 for rotary. The break point was clearly demonstrated at about 11 min (conduction slope=0.4). After a lag of about 7 min pregelatinized cracked wheat demonstrated pure conduction heating (slope=4.9) regardless of retort type. Students produced examples of convection, conduction and broken line heating in a hands-on laboratory exercise. The authors will provide copies of the laboratory exercise, results and student evaluations on CD ROM.
Session 11, Education: Food Science Education
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