Food Microbiology chpt 1

Question 1

What are microorganisms found in food?

Answer 1

viable spores, bacteria, viruses, parasites yeasts, molds, viable nonculturable

Question 2

How do Microorganisms get into food?

Answer 2

1. Soil
2. Water (E.coli)
3. Humans ( Staphylococcus aureus, Cross contamination)
4. Utensils
5. Intestinal tract of humans and animals (meat, veggies and water contamination)
6. Air, dust

Question 3

Explain what microorganism could be found in vacuum packaged hot dogs

Answer 3

• Stored in fridge, it was due to air condition unit that was cleaned. However, people got listeriosis.
  Listeria monocytogenes

Question 4

What is bacteria that is associated with foods called?

Answer 4

Chemoheterotrophs

- Use organic compounds to grow/ produce ATP.

Question 5

If an organism is fastidious it is..?

Answer 5

Has a complex nutritional requirements

LAB

Question 6

What is a microorganism that can cause spoilage to all food?

Answer 6

Pseudomonas

Question 7

What does bacteria need in food to grow?

Answer 7

water, CHO, nitrogen source, ammonium cholirde, potassium, magnesium, iron ect

Question 8

What will inhibit growth of bacteria?

Answer 8

NOT nutrients b/c food is abundent in nutrients.
Intrinsic factors: pH, Aw, salt concentration
Extrinsic factors: temp and aerobic/anaerobic conditions

Question 9

With a microbial growth curve, what phases do you want to slow down, and what phase do you want to extend?

Answer 9

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)

Question 10

What does growth rates determine?

Answer 10

1. How fast a food might spoil.

2. How fast a food ferments

Question 11

What is generation time?

Answer 11

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

Question 12

Gram stains! What is the difference between gram positive and gram negative

Answer 12

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

Question 13

How do you perform a gram stain?

Answer 13

1. Heat culture, smear by passing slide through fame.
2. Flood with crystal violet, wash (All cells purple)
3. Flood with iodine solution (All cells purple)
4. Decolorize with alcohol (Gram + purple, Gram - no color)
5. counterstain with safranin (gram + purple grapm - red)

Question 14

What is the 1st step to characterize microorganisms?

Answer 14

GRAM STAIN

Question 15

Yeast

Answer 15

Nonfilamentous, 
Unicellular fungi 
Sexual (binary fision)
Asexual ( budding)
ex. Saccharomyces (brewing and backing, food spoilage)

Question 16

Molds

Answer 16

• 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

Question 17

Virus

Answer 17

• 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

Question 18

Parasites

Answer 18

* 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.

Question 19

Protozoa

Answer 19

Single cellular animals can cause infections
- have cysts or oocysts that surive outside host.
ex. Entamoeba histolytica
Giardia lamblia
Cryptospordium parvum

Question 20

Food spoilage

Answer 20

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.

Question 21

Perishable foods regulations must haves:

Answer 21

Packaged foods: storage life < 90 days, BBD

Retail storage life < 90 days, Packed on date

Question 22

What does BBD indicate?

Answer 22

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.

Question 23

Foodborne Disease is either intoxication or infection..what is the difference?

Answer 23

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.

Question 24

Why is food fermenation important?

Answer 24

25% of foods are fermented.

Question 25

How does raw meat spoil?

Answer 25

Via protein degradation if stored in oxygen

Question 26

Bread spoilage?

Answer 26

Mould growth

Question 27

Oil spoilage?

Answer 27

Lipid rancidity due to oxidation (chemical)

Question 28

Yogurt spoilage?

Answer 28

Too much acid LAB, mould growth