Definitions Flashcards
Microbiology
The study of microscopic organisms
Food Microbiology
The study of biochemical, physiological and ecological interactions of microorganisms with food
Activities of a food microbiologist
- predict types/ numbers of microorganisms associated with a food
- isolate/ identify microorganisms from food
- detect microbially produced toxins
Activities of a food microbiologist (cont.)
- identify changes in food attributable to microbial growth
- predict growth/ survival of microorganisms in a food product, based on intrinsic & extrinsic parameters of the food
- Inhibit microbial growth to extend product quality/ shelf-life
Employment of Food Microbiologists
- Industry
- Academia
- Government
Free-living organisms
Can be cultivated using laboratory media
Unicellular (Prokaryotes)
- Cell wall: protein, lipid, peptidoglycan (rigidity)
- Cell membrane: Lipid bilayer (respiration)
- No nuclear membrane
- Circular DNA
Bacterial Size
- measured in microns
- μm, > 10^6
Bacterial Multiplication (Binary fission)
-Growth Rate: 20 min
Bacterial Growth Requirements (6):
- Nutrient Source (food)
- Carbs (energy)
- Carbon
- Nitrogen
- Vitamins
- Trace minerals, sulfur, phosphorus
Growth Curve
Lag, Log, Stationary, Death
Lag
Physiological adaptation to new environment
Log
Rate of increase, function of absolute cell number, exponential
Stationary
Steady-state equilibrium, rate of cell growth is exactly balanced by rate of cell death
Death Phase
Occurs because vegetative cells can survive exposure to harsh conditions (few nutrients or too many toxins) for only so long
Psychrophylic Growth Temp
- ≤0°C (optimum 10-15°C)
- e.g. Vibrio spp
Psychrotrophic Growth Temp
- 0-7°C (optimum 30-35°C)
- e.g. Spoilage = Pseudomonas, Pathogens = Listeria, Yersinia, Vibrio
Mesophilic Growth Temp
- no growth at 4°C, optimum at 30-37°C
- e.g. Pathogens = Salmonella, E. coli, Shigella,
Thermophilic Growth Temp
- growth at temperatures >45-50°C (optimum at 55-65°C)
- e.g. Some starter cultures
Enterobacteriaceae
Enteric, Gram negative rod, Anaerobe, peritrichous flagella
Coliforms
- Produce gas from lactose
- E.g. E. Coli
Non- Coliforms
- Doesn’t produce gas from lactose
- E.g. Salmonella
Eukaryotes
- Cell wall absent
- Nuclear Membrane
- Strands of DNA
- Sexual/asexual
- Respiration: mitochondria
Yeasts
Unicellular Fungus
