Microorganisms: Bacteria, Malolactic Fermentation, spoilage, and problem fermentations Flashcards
(14 cards)
What two bacteria are especially important to wine making
Lactic Acid bacteria
Acetic Acid Bacteria
Why is lactic acid bacteria important to wine making?
they contribute important flavor characteristics to foods
What are the four main lactic acid genera important to wine making and which is most important
Lactobacillus
Pediococcus
Leuconostoc
Oenococcus
What do lactic caid bacteria contribute to wine
Lactic Acid, converted from malic acid
grapes are one of few fruits that contain malic acid
What is malolactic fermentation
Lactic acid microorganisms convert the malic acid in grapes into lactic acid and CO2 through the process of malolactic fermentation
What is the affect on wine of Malolactic fermentation
Because the process converts a compound (malic acid) with two functional groups of acid to a compound with only one group of acid (lactic acid) the wine becomes less acidic
The process also sabilizes the wine making it less susceptible to growth of spoilage microorganisms
The process also forms an aroma compoound called diacytel , buttery aroma
How can the winemaker control spontaneous malolactic fermentation
- Use sulfur dioxde (SO2)
- Use Lysozyme - an anzyme that breaks down the proteins in bacteria
- Filtration - filter out microorganisms
What is primary fermentation?
Alcoholic fermentation by yeast to convert sugars to alcohol and CO2
What is secondary fermentation
Malolactic fermentation where malic acid is converted to lactic acid and CO2
What is acetic acid?
Acetobacter Aceti converts ethanol into acetic acid, the main acid in vinegar.
Gives wine a nail polish aroma
How can winemakers prevent/control the presence of acetobacter
Conversion of ethanol to acetic acid requires oxygen, so winemakers try to exclude air.
- Keep wine containers as full as possible to eliminate headspace
- Addition od SO2
What is Brettanomyces Bruxellensis
spoilage microorgansim that gives “barnyard” characteristics
May be desirable in low levels in some wines
controlled by addition of SO2 or filtration
What is a sluggish or stuck fermentation?
Fermentations slows or stops prior to consumption of all sugars
Why is a sluggish or stuck fermentation undesirable?
produces a sweet wine which may not be desirable
microbilogically unstable
