Lecture 8 - Food Microbiology Flashcards
What are the types of microbes in our food?
Bacteria/Virus/Fungi/Protozoa
What are some common shapes of bacteria?
Round (Cocci)
Rod-Shaped (Bacilli)
Curved-Shaped (Spirilla)
What is the purpose of gram staining?
Bacteria Identification
What are gram positive cells?
Cells have a larger and more highly cross-linked peptidoglycan
What are gram negative cells?
Cells that do not possess a peptidoglycan layer
What are the factors that affect microbial growth?
- Food composition/ Availability of nutrients
- pH
- Availability of oxygen
- Temperature
What is the minimum water activity required for bacteria growth?
0.60
Which type of bacteria has a higher minimum water activity? Gram positive or gram negative?
Gram Negative
Do bacteria require higher or lower water activity and pH for growth compared to yeast and moulds?
Higher
What is the minimum number of bacteria cells per gram in order to cause food spoilage?
10 million cells per gram
What are food spoilage microorganisms?
Microorganisms that produce undesirable aromas, colour defects and slime formation and renders a food to be unsafe for consumption
What are some of the causes of food associated outbreaks?
Improper storage temperatures
Poor personal hygiene
Inadequate cooking temperatures
Cross-contamination
Contaminated raw materials
What are some of the hurdles that inhibit the growth of microbes?
High temperature (for psychrophiles)
Low temperature (for thermophiles)
Reduce water activity
Addition of preservatives (sucrose, sodium chloride, lactic acid, hydrogen peroxide, nitrates)
What is the microorganism responsible for the fermentation of barley to make beer, ferment grapes to make wine and to bake bread?
Saccharomyces Cerevisae
What is the microorganism responsible for pickling cucumbers?
Lactobacillus plantarum
