lecture 14

lecture 14 - FOOD SCIENCE 4010-Lecture 14 Heat...

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FOOD SCIENCE 4010--Lecture 14 Heat Sterilization PRINCIPLES: Commercial sterilization is the killing of all pathogenic and spoilage microbes in a food. 4 types of microbes: Pathogenic, spoilage, free-riders, and fermentative Usually kill ¾ but don’t really care about free-riders Commercial sterilization is achieved by heat All pathogens are killed by intense heat… most concerned about Clostridium botulinum in canning Problem: effects sensory and nutritional quality … texture, color, and flavor differences in fresh and canned W/ fresh asparagus naturally break @ a point where the spear is good Canned foods are sterile while other foods are not A thermal death curve plots microbial survival as a function of time at a given temperature. Fig 1.14 , 12.7 D-values (min 90%, 1 log reduction), Z-values (# of degrees for a specific death time curve to pass through 1 cycle), and F-values (# of min at a specific temperature for specific bacteria at specific Z value) - # of minutes required to destroy a known population of microorganisms in a given food under specified conditions Z- value – specific temp vs. D-value Canning is a 12-D process. Goes through 12-D steps 1-D – 90% 2-D – 99% 3-D 99.9% 12-D =99 w/ 10 9’s behind it Cold point – geometric center of the can when we’re talking conduction – molecule to molecule 1/3 from the top or 1/3 bottom… can be either … get currents going and the currents change it. . when you have liq/ sol = particulates – more challenging ex: peas… asparagus
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lecture 14 - FOOD SCIENCE 4010-Lecture 14 Heat...

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