Lecture 1 Flashcards
What are the 3 main microorganisms in food?
Mould
Bacteria
Yeast
What is yeast?
One cell microorganisms Reproduced by budding Grow best in the presence of: -moisture -O2 -Sugar -Acidic pH
Ferments sugar into alcohol and CO2
What food is yeas important in?
Bread
Wine
Beer
What is a mould?
Multicellular and filamentous
Reproduce by spores
Grow on dry food, cereals, grains (unique to them)
Can grow at room temp or cold temps
What food is mould important in?
Cheese and soy sauce
What are the different bacterial morphologies?
Cocci diplococci Sarcina Staphylcocci Streptococci Rods Vibrio
What are 2 important factors that are important to microbial growth?
Extrinsic Factors
Intrinsic factors
What are extrinsic factors?
Depends ono the storage environment such as:
- Temp
- HUmidity
- Envrionmental Gases(O2, CO2)
What are intrinsic factors?
Properties inherent to food to help protect them such as:
- biological structure (skin, shell)
- pH, water activity, anti-microbial compounds, nutrients
What are the 2 kinds of water activity?
Higher the free water the higher the water activity
○ Free water available for physical and chemical reactions
○ Bound water bound to sugars and not able to participate in andy chemical reactions
How can low water activity be brought about?
Dehydration
Addition of Salt or sugar (binds water to make in unavailable)
What water activity do most fresh foods have?
0.96-0.99
Bacteria that causes food-born illness will grow on foods that have a water activity of what?
0.85 and above
What are the 3 temp categories that bacteria like to grow at?
Psychrophilic Cold
Thermophilic >40C
Mesophilic ~30C
How do we classify bacteria based on their need for O2?
Aerobic or Microaerophile (likes small % of O2)
Anaerobic
Facultative (can grow in presence or absence of O2)
What are spore formers?
Bacteria form spores around themselves to protect against harsh environment
Can have dorment spores, activated in better conditions
In general what do molds require for growth?
O2
What conditions does yeast grow best in?
Aerobic
What is food spoilage?
Indicative of deterioration in taste, smell, sight and texture
-deterioration of sensory products
How can spoilage occur?
Chemical reaction: oxidation of fats causes rancidity
Physical change: bruising/dehydration
Microbial growth
What are the typical indications of food spoilage?
Mold growth Gas Slime Off odour Off Flavour
What is the most common off odour ?
Smell of ammonia, sulphides and hydrogen sulphide
-typical smell of eggs
What is the most common off flavour?
Acidic
Bitter
Not fresh
What is the most common off texture?
Slimy
Mushy
What are the heat propterties of E coli?
can grow/live in cold but is heat sensitive
What is a toxin producing mold?
Aspergillus produces aflatoxin which can causes liver cancer
-common in peanut production
Where do we mostly see viruses?
Cheese
Raw shellfish
What is the most common parasite?
trichinella round worms
-typically found in pork
What are the 5 main practices in food handling?
- People will communicable diseases and skin lesions should never handle foods
- When handling food, person must wear clean (white) clothing and head cover
- When handling foods, hands should not touch mouth, nose or any other part of the body
- When handling foods, person should not eat, drink smoke sneeze or cough
- Pets and other animals should be kept away from food processing area
What is the danger zone?
4-60C
What is bacterial growth rate?
Change in the #/time
What is bacterial generation time?
Doubling time of the population size
What is binary fission?
One cell divides into 2 cells
What is the logistic growth rate of bacteria?
Lag phase
Log phase
Stationary phase
Death Phase
In reality how bacteria grow
How does fermentation preserve food?
pH reduction
Alcohol production
O2 reduction
Microbial inhibitors
Fermentation produces desirable changes in which characteristics of food?
Flavour
Texture
Nutritional Value
What is the definition of fermentation?
Breakdown of Carbs to yield:
- lactic acid
- Alcohol
- Acetic acid
- CO2
What is the difference between control fermentation and wild fermentation?
Control: We know the type of bacteria added and know what will happen.
Wild: you don’t know anything
What is lactic acid fermentation?
Simple sugars to lactic acid
What re the bacteria genera involved in fermentation?
Lactococcus Lactobacillus Leuconooostoc (butter flavour) Pediococcus Streptococcus
What food items are able to ferment?
Dairy: yogurt
Meat: cured sausage (salami)
Veg: pickles, sauerkraut, olives
What its Koji fermentation?
For soy sauce
Aspergillus oryzae mold is added to beans to break down protein and carbs
Then lactobacillus is added to break down into simple sugars
Yeast is added to reduce the sugar to alcohol
What is alcoholic fermentation?
Sugar is converted to CO2 and alcohol with saccharoomyces species
-anaerobic process
Whiskey, brandies and gins are produced by distilling off what?
The alcohol from materials that have been fermented by yeast
What is acetic acid fermentation?
Alcohol + OO2 gives water and acetic acid (vinegar)
What is Coo2 fermentation?
Sucrose broken down into glucose and fructose which is further broken down into CO2 and alcohol with the use or Saccharomyces cereviisiiae
