Lec 6 & Chp 6 Flashcards
What is a psychrophile? What temperature do they grow in?
“cold loving”
grow between 0° C
What are the two groups of Psychrophiles? What temp. do they grow in? What are they responsible/or not for?
True Psychophiles:
15°C or less
rarely cause food spoilage
Psychotrophs:
20-30°C
responsible for most low temp. food spoilage
Mesophile? What do they include? What temp do they grow in?
moderate temp loving
grows between 10°-50°C but opt growth is 25-40°C
includes pathogens & common food spoilage organisms
thermophiles? opt growth temp?
“heat loving”
50°-60°C
found in hot springs and organic compost
hyperthemophiles? opt growth temp?
“extreme thermophile”
>80°C
found in hot springs associated w/ volcanic activity
What pH do most bacteria grow in? molds and yeasts?
- 6.5-7.5
- pH 5-6
acidophiles
bacterium that grow below pH 4
- tolerant of acidity
what does acidity do?
inhibits most microbial growth
- used in food preservation (pickling)
Osmotic Pressure
pressure applied to solution side to stop fluid movement when semi-membrane seperates solution from pure water
hypertonic solution? what is it used for?
high osmotic pressure removes water from cell, causing shrinkage of cell membrane
- used to control spoilage and microbial growth
ex: salt on meat
plasymolisis
process in which cells lose water due to a hypertonic solution
hypotonic solution?
low osmotic pressure causes water to enter cell
extreme/obligate halophiles
require high osmotic pressure
facultative halophiles
don’t require, but tolerate high osmosis pressure
What are the main chemical requirements for microbial growth?
carbon
nitrogen
sulfur
phosphorus
other elements: (potassium, magnesium, calcium)
trace elements: iron, copper,
