Food Microbiology chpt 1 Flashcards
What are microorganisms found in food?
viable spores, bacteria, viruses, parasites yeasts, molds, viable nonculturable
How do Microorganisms get into food?
- Soil
- Water (E.coli)
- Humans ( Staphylococcus aureus, Cross contamination)
- Utensils
- Intestinal tract of humans and animals (meat, veggies and water contamination)
- Air, dust
Explain what microorganism could be found in vacuum packaged hot dogs
- Stored in fridge, it was due to air condition unit that was cleaned. However, people got listeriosis.
Listeria monocytogenes
What is bacteria that is associated with foods called?
Chemoheterotrophs
- Use organic compounds to grow/ produce ATP.
If an organism is fastidious it is..?
Has a complex nutritional requirements
LAB
What is a microorganism that can cause spoilage to all food?
Pseudomonas
What does bacteria need in food to grow?
water, CHO, nitrogen source, ammonium cholirde, potassium, magnesium, iron ect
What will inhibit growth of bacteria?
NOT nutrients b/c food is abundent in nutrients.
Intrinsic factors: pH, Aw, salt concentration
Extrinsic factors: temp and aerobic/anaerobic conditions
With a microbial growth curve, what phases do you want to slow down, and what phase do you want to extend?
Extend the lag phase (numbers aren’t increasing)
Slow down the exponential growth phase
Stationary phase is high # but not growing at least
(see notes for graph)
What does growth rates determine?
- How fast a food might spoil.
2. How fast a food ferments
What is generation time?
Generation time is the time it takes for the population to double. (Useful for comparative purposes).
Generation time can give you Number of generations. n= T/ GT
Gram stains! What is the difference between gram positive and gram negative
Gram positive has a cell membrane with a thick layer of peptidoglycan and no outer cell wall.
Gram Negative: Has an outer cell wall, cell membrane has a thin layer of peptidoglycan
How do you perform a gram stain?
- Heat culture, smear by passing slide through fame.
- Flood with crystal violet, wash (All cells purple)
- Flood with iodine solution (All cells purple)
- Decolorize with alcohol (Gram + purple, Gram - no color)
- counterstain with safranin (gram + purple grapm - red)
What is the 1st step to characterize microorganisms?
GRAM STAIN
Yeast
Nonfilamentous, Unicellular fungi Sexual (binary fision) Asexual ( budding) ex. Saccharomyces (brewing and backing, food spoilage)
Molds
- Filamentous
- Grow over range of temp and moisture
- septate hyphae mostly
- sporulating (spread by air)
- good in cheese and fermented products
- causes disease in pple (mycotoxins)
- extremely important cause of food spoilage
Virus
- Very small
- genetic material eitehr DNA or RNA
- surrrounded by protein coat
- sometimes have lipid envelope
- are “parasites” cannot carrry out chemical rxns/ reproduce as self sufficient organisms
- transmitted through foods.
- -> cross contamination, workers not washing hands
Parasites
* DO NOT GROW IN FOOD*
- host is necessary for growth and reproduction
- causes serious illness
Trichinella spiralis (from wild game)
–> Control by cooking meat > 65C ( 70C internal)
- Some cysts destroyed by freezing.
Protozoa
Single cellular animals can cause infections
- have cysts or oocysts that surive outside host.
ex. Entamoeba histolytica
Giardia lamblia
Cryptospordium parvum
Food spoilage
Relates to food composition
Lipids= Rancid
–> Oxidative (peroxides fishy smell) chemical
–> Hydrolytic FFA (microbial)
Proteins: proteolysis (microbial)
putefaction (ammonia, H2S, amines)
CHO: Fermentation (microbial), organic acids causes souring.
Perishable foods regulations must haves:
Packaged foods: storage life < 90 days, BBD
Retail storage life < 90 days, Packed on date
What does BBD indicate?
The quality of the food, but NOT food safety. Gives consumer idea of how old the food is. Won’t change food quality until BBD.
Foodborne Disease is either intoxication or infection..what is the difference?
Intoxication is a toxin produced in the food, food ingestdd and illness occurs (happens quick). ex. Bacillus cereus, Clostridium botulinum,C. perfingins Staphylococcus aureus mold toxins ( aflatoxin)
Infection:Food is infected with organism, food eaten, organism colonizes GI track, illness occurs (takes a couple days) Campylobacter jejuni Enteropathogenic Escherichia coli Enterohemorrhagic E. coli Listeria monocytogenes Salmonella spp.
Why is food fermenation important?
25% of foods are fermented.
How does raw meat spoil?
Via protein degradation if stored in oxygen
Bread spoilage?
Mould growth
Oil spoilage?
Lipid rancidity due to oxidation (chemical)
Yogurt spoilage?
Too much acid LAB, mould growth
