Ch17 Flashcards
perishable foods
semi perishable foods
non-perishable foods (give ex. of all)
food that easily supports the growth of microorganisms (raw meat/ green salad)
food that does not spoil as easily (nuts/ potatoes)
food that prevents the growth of microbes because that lack water (flour/sugar/ dried beans)
What causes food to spoil?
growth of bacteria in food
The likelihood of food spoiling depends on:
Intrinsic factors (the characteristics of the food itself)
Extrinsic factors (the way the food is stored)
Why are refrigerators used to store foods
They slow the growth of pathogens that grow better in room temperatures
Is dry or moist food more perishable? Why?
Moist foods; the water content
What is water activity? What is the water activity of fresh foods? What water activity do most spoilage bacteria require? What food have a lower water level
The amount of water accessible to microorganisms (a(↓w))
>.99 a(↓w)
.91
dry foods and foods that have a high solute content (like sugar/salt)
enterotoxins
What water level can the microbe that makes this thrive?
secreted by S. aureus; act on the intestine causing foodborne illnesses
.86 (a(↓w))
State the typical spoilage patterns of:
fruits/vegetables
fresh meat/ poultry/ seafood
milk
pectin being hydrolyzed
sugars being fermented
proteins undergoing proteolysis/deamination
carbohydrates being hydrolyzed
lactose being hydrolyzed/ fermented
proteins (casein) undergoing proteolysis/deamination
Is mold spoilage more common in vegetables or fruits? Why?
Fruits, since it is more acidic
What phases of microbial growth determine food spoilage?
What methods are done to prevent food spoilage?
lag phase @ beginning as well as the exponential phase
EXTENDING lag phase/ reducing microbial growth
changing pH
storage temperature
What can be done to prevent food spoilage?
drying meat/ fruit in sun
SMOKING meat
adding high amounts of salt/sugar
heating/ refrigeration
lyophilization
freeze-drying; food is frozen & dried under a vacuum
What are bacteria that can tolerate refrigerator temperatures described as? (give an ex.)
psychrotolerant; Listeria (L.) monocytogenes
What did Nicolas Appert do?
responsible for canning (food sealed inside a jar was heated in boiling water for hours, undergoing HIGH HEAT processing)
botulism
What was done as a solution for this?
disease caused by Clostridium bacterium
associated with contamination of food in early canning procedures
D value (time required to kill 90% of target organisms was studied)
pasteurization
heat processing/ partial sterilization of the food product
(heating/irradiating/ applying high pressure)
not high heat processing like canning
pickling
irradiation
bacteriocins
process of lowering PH of a food by storing/ marinating in chemicals like vinegar
exposing food to radiation
products releases by microbes to kill other microbes
modified atmosphere packaging
(MAP) vacuum packaging, the atmosphere around food is altered to extend shelf life
What technology is implemented when modified atmosphere packaging when microbes like C. botulinum can thrive in these environments?
(describe it)
(give an example)
hurdle technology; constraints that the microbe must overcome to thrive; changing pH levels/ water availability/changing gas concentrations, etc.
starter cultures
microorganisms added to frood to help in the production of FERMENTED products
BRIEFLY describe milk/vegetable/meatfermentation
lactic acid bacteria (LAB) is prevalent in food fermentation like yogurt, kefir, cheese, sauerkraut, etc.
Briefly go through the steps from milk to yogurt
- start with milk
- adjust fat content
- pasteurization
- adding starter cultures
- ferment as lactose sugars change into lactic acid
- add fruit/ sweeteners
Why are starter cultures usually mixed?
Natural microbes are, not always reliable, so microorganisms with intended strains are added
rennin
protease/enzyme that results in the curding of milk
(addition with whey results in cheese)
