Lecture+22+food+preservation+_color_

Lecture+22+food+preservation+_color_ - Review: MOLDS YEASTS...

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Review: MOLDS YEASTS LACTIC ACID BACTERIA ENDOSPORE BACTERIA ENTERICS PSEUDOMONAS A W 0.6 0.6 0.9 0.93 0.94 0.97 pH 1.5 1.5 3.5 4.5 (3.7) 4.5 5.5 temperature no thermophiles some psychrotrophs no thermophiles some psychrotrophs some marginal thermophiles some psychrotrophs several thermophiles some psychrotrophs No thermophiles few psychrotrophs (1 pathogen) no thermophiles many psychrotrophs Oxygen tolerance aerobe aerobes (aw <0.8), others are facultative microaerophile mixed facultative aerobe other grow relatively slowly, break down high MW compounds grow faster than molds, prefer high sugar foods predominate in low O 2 , including refrigeration spores survive cooking Erwinia is a member major in spoiled raw products, grow on protein/fat
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Most food pathogens belong to Enteric & Endospore -forming bacterial groups. Safety Concerns (page 107) Spoilage conditions which encourage either of these might also be a safety concern Example: Salmonella in meat ( Shigella might be present but won’t grow) Staphylococcus aureus Pathogens–Not in spoilage groups Habitat: Human/animal skin Most similar to the “endospore forming” group Produces lipases and proteases Similar growth rate Tolerance: oxygen tolerant (facultative anaerobe) pH 4.5 low a w (0.86) but toxin production (0.93) 7–48 o C= growth (enterotoxin:10–46 o C)
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In general, pathogens do NOT grow: Below a w of 0.85 ( S. aureus ) Below pH of 4.5 Above temp of 60 o C( C. perfringens ) Environmental limits of food pathogens Pathogens are either facultative anaerobes and obligate anaerobes Therefore, no redox potentials are safe from pathogens except extremely high or low redox QUIZ (Number 4) 1. Which group of microorganisms (discussed last Friday) is likely to cause spoilage of fresh whole oranges stored for weeks at 25 °C? ANSWER: MOLDS On a sheet of paper: Name, SID#, and answer. (5 points) 2. What is the Redox (Eh) range for most aerobes ? ANSWER: +100 to +400 mV (because of ambiguity on the slides, credit (for this quiz) Was given when a lower limit of -50 mV was written)
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Controversial Food Preservation Bokyung Lee 3/5/2012 FST104 (Food Microbiology)
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Food preservation • the process of treating and handling food in a way that
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Lecture+22+food+preservation+_color_ - Review: MOLDS YEASTS...

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