NU FS363 Lecture Notes - Lecture 17: Food Spoilage, Food Preservation, Pasteurization
6 Jan 2017
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Lecture 17 + 18 thermal and non-thermal processing. To understand principles of microbial death curves due to thermal processes. To know how to apply these processes in the control of microorganisms in foods. Do all relevant calculations, including d- and z-values, and be able to apply them to practical situations. Growth inhibition or microbial death? (first question to answer if you choose preservation) Growth inhibition (bacteriostatic) keep cell count stable and prevent spoilage. Staphylococcus aureus is always in processed foods but need a high count to produce toxins, Clostridium perfringens, etec pulsed electric fields high pressure aseptic packaging, microfiltration irradiation refrigeration chemical preservation pasteurization, canning. Salmonella (low cell counts) will make people ill (can be <10 cell counts), campylobacter, shigella. To get a safe product, need to kill it. Inhibition of bacterial growth (cold, low aw, low ph) Bacteria resume growth when conditions change (temperature abuse) Pathogens remain alive (enterohaemorrhagic e. coli on beef, salmonella on poultry, produce)
