Brewing Microbiology Flashcards

1
Q

List 5 factors that influence microbial growth

A

Oxygen
Ph
Temperature
Nutrients
Moisture
Selective chemicals

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2
Q

What is a microorganism?

A

Plant or animal of microscopic size

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3
Q

What is a eukaryote?

A

Cell containing genetic material in a membrane enclosed structure (nucleus)

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4
Q

What is a prokaryote?

A

Cell lacking a true nucleus

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5
Q

T/F: yeasts, fungi, plants, and animals are eukaryotes

A

True

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6
Q

In brewing, what is a contaminant?

A

All microorganisms other than cultured yeast

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7
Q

Where do brewery microbes exist?

A

Everywhere

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8
Q

What are bacteria?

A

Single celled prokaryotes

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9
Q

What are the main shapes of bacteria?

A

Coccus (round)
Rod (cylindrical)
Curved rods (spiral)
Spiral helix

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10
Q

What shape are pediococcus bacteria?

A

Round (coccus)

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11
Q

What shape are bacilli bacteria?

A

Rods (lactobacillus)

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12
Q

What is the name of ale yeast?

A

Saccharomyces cerevisiae

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13
Q

What is the name of lager yeast?

A

Saccharomyces pastorianus

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14
Q

What are the three types of fungi?

A

Fusarium, penicillium, aspergillus

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15
Q

Are molds aerobic or anaerobic?

A

Aerobic

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16
Q

What are mycotoxins?

A

Toxic, potentially carcinogenic fungi of which several are heat stable (survive boil)

17
Q

What is fusarium?

A

A red mold on barley that produces a mycotoxin called deoxynivalenol (DON)

18
Q

What are the stages of microbial growth?

A

Lag, exponential (log), or stationary

19
Q

Why is beer a worse environment for microbial growth than wort?

A

Lower ph
Low o2
High co2
Ethanol
Hops

20
Q

What are 2 gram positive bacteria?

A

Lactobacillus
Pediococcus

21
Q

What are 2 gram negative bacteria?

A

Zymomonans
Megasphaera
Gluconobacter

22
Q

What is a gram stain based on?

A

Positive - thicker wall - monoderms
Negative - thinner or no wall - diderms

23
Q

What is a traditional method for identifying spoilage bacteria?

A

Microscopy followed by plating
Catalase test

24
Q

What is a modern test for identifying spoilage bacteria?

A

ATP
PCR
Volatile Organic Acid (VOA)

25
Q

Why are wild yeasts important?

A

Sometimes you want wild yeast for certain flavors