Name the 4 categories of bacteria
- Harmful/disease causing (aka pathogens)
- undesirable (aka putrefying)
- beneficial
- benign
Does food change taste/appearance once contaminated w/ pathogens?
no
What type of bacteria accelerates decomposition of food?
undesirable
True or false - undesirable bacteria causes food borne illness
false
What food is beneficial bacteria used to produce?
- yoghurt
- sauerkraut
- cheese
- cultured milk
What is the most common type of bacteria?
-benign
What are spores?
-bacteria that forms a shell around itself and remains dormant until conditions are favourable to continue growth
Name 3 spore forming pathogens
- tetanus
- anthrax
- botulism
What is the name of the process of microorganisms splitting in 2?
-binary fission
Ideal conditions for the rapid multiplication of microorganisms
- warmth
- moisture
- nutrients
Name the 4 stages of bacterial growth
- lag (adjusting to conditions)
- log (ideal rapid growth)
- stationary (used up nutrients)
- death (used up nutrients)
6 conditions necessary for growth of bacteria
- Food
- Acidity (low, >4.6 pH)
- Time
- Temperature (warm, in general - 41-140)
- Oxygen
- Moisture (high)
Foods bacteria thrives on
- protein based
- cooked plant based (eg. POTATO)
- seed sprouts
- garlic in oil
Name the bacteria that need
a) oxygen
b) no oxygen
c) ambivalent to oxygen
a) aerobes
b) anaerobes
c) facultatives
What is the name of the bacteria that thrives in the cold (<50)
psychrophilic
What is the name of the bacteria that thrives in temp 50-110
mesophyllic
What is the name of the bacteria that thrives in temp 110-150
thermophilic
How do bacteria absorb water?
in liquid form through their cell wall
How does one remove moisture from food?
- dehydration
- smoking
- freezing
- preserving w/ salt/sugar
What is the difference between water content and water activity value?
water content measures actual amount of water whereas water activity value measures amount of water available for biological activity
At which water activity value does food not have enough moisture to support bacteria?
<8.5
Name 4 methods of destroying bacteria
- heat
- refrigeration (doesn’t destroy but slows growth)
- air/sunlight (ultraviolet/lack of moisture)
- chemicals (germicides/bactericides)
Name 2 ways of pasteurizing milk
- holding method: 145 for 30 min
- flash method: 161 F for 15 sec
What is the most popular chemical used to kill bacteria
chlorine
