Brewing Microbiology Flashcards
List 5 factors that influence microbial growth
Oxygen
Ph
Temperature
Nutrients
Moisture
Selective chemicals
What is a microorganism?
Plant or animal of microscopic size
What is a eukaryote?
Cell containing genetic material in a membrane enclosed structure (nucleus)
What is a prokaryote?
Cell lacking a true nucleus
T/F: yeasts, fungi, plants, and animals are eukaryotes
True
In brewing, what is a contaminant?
All microorganisms other than cultured yeast
Where do brewery microbes exist?
Everywhere
What are bacteria?
Single celled prokaryotes
What are the main shapes of bacteria?
Coccus (round)
Rod (cylindrical)
Curved rods (spiral)
Spiral helix
What shape are pediococcus bacteria?
Round (coccus)
What shape are bacilli bacteria?
Rods (lactobacillus)
What is the name of ale yeast?
Saccharomyces cerevisiae
What is the name of lager yeast?
Saccharomyces pastorianus
What are the three types of fungi?
Fusarium, penicillium, aspergillus
Are molds aerobic or anaerobic?
Aerobic
What are mycotoxins?
Toxic, potentially carcinogenic fungi of which several are heat stable (survive boil)
What is fusarium?
A red mold on barley that produces a mycotoxin called deoxynivalenol (DON)
What are the stages of microbial growth?
Lag, exponential (log), or stationary
Why is beer a worse environment for microbial growth than wort?
Lower ph
Low o2
High co2
Ethanol
Hops
What are 2 gram positive bacteria?
Lactobacillus
Pediococcus
What are 2 gram negative bacteria?
Zymomonans
Megasphaera
Gluconobacter
What is a gram stain based on?
Positive - thicker wall - monoderms
Negative - thinner or no wall - diderms
What is a traditional method for identifying spoilage bacteria?
Microscopy followed by plating
Catalase test
What is a modern test for identifying spoilage bacteria?
ATP
PCR
Volatile Organic Acid (VOA)
Why are wild yeasts important?
Sometimes you want wild yeast for certain flavors
