MICR-4070 Lecture Notes - Lecture 12: Thermal Death Time, Magnetic Ink Character Recognition, Microbiology
Document Summary
Micr 4070: food and dairy microbiology, test 2 (lecture 3: physical preservation methods) Factors affecting thermal death (continued from lecture 2) Nature of the food: chemical composition-e. g proteins, carbohydrates, fats, etc. Macromolecules can bind to water and prevent damage: aw- available water for bacteria to use. The lower the aw, the fewer deaths (aka more heat resistant: ph. Microbes are more sensitive at a low ph, especially in the presence of acetate, lactate, or propionate. Thermal death time (tdt): the time necessary to kill a given number of organisms at a specified temperature: population size dependent. D value: the time required to destroy 90% of the organisms at a specified temperature. Wednesday, march 21, 2018: make sure to include what temperature is being used, population size independent, steeper slopes indicate shorter times. When using these, the effect on the food needs to be considered.