Microbial Stability Flashcards
(24 cards)
Why is microbial stability important before bottling?
To prevent spoilage, off-flavors, refermentation, and quality loss after bottling.
What are the key spoilage microbes in wine?
Brettanomyces, Acetobacter, Pediococcus, Lactobacillus, and film yeasts.
What is cold stabilization and its microbial benefit?
Reduces tartrate crystals and lowers microbial populations in cold-sensitive organisms.
What is the role of SO₂ before bottling?
Inhibits microbial growth and acts as an antioxidant.
How does pH affect microbial stability?
Lower pH enhances the effectiveness of SO₂ and reduces microbial activity.
Why is hygiene critical in the bottling line?
Any contamination can result in spoilage post-bottling; cleanliness is key to sterility.
What is cross-flow filtration?
A pre-bottling filtration method that removes microbes while preserving wine integrity.
How can dissolved oxygen be controlled before bottling?
Use of inert gas blanketing and careful handling to limit oxidative spoilage.
What is sterile filtration?
A physical method (typically 0.45 micron) to remove all microbes before bottling.
When is sterile filtration essential?
For off-dry, sweet, or low-SO₂ wines vulnerable to refermentation or spoilage.
What are the benefits of SO₂ additions?
Long-lasting microbial inhibition and protection against oxidation.
What are the drawbacks of sterile filtration?
Possible flavor stripping or textural changes; requires clean environment.
How does SO₂ effectiveness vary by pH?
More effective at lower pH due to higher proportion of molecular SO₂.
Can sterile filtration replace SO₂?
It can reduce the need for high SO₂, but SO₂ is still often needed for post-bottling protection.
How can winemakers balance both methods?
Use sterile filtration to ensure microbial safety, and minimal SO₂ for antioxidant and residual protection.
What is the difference between sterile and membrane filtration?
Sterile removes all microbes (0.45 μm); membrane is broader and includes other pore sizes.
How can closures impact microbial stability?
They determine oxygen ingress and risk of microbial growth in headspace or under closure.
What closure is most effective at preventing spoilage?
Screwcaps and technical corks with consistent seals reduce microbial ingress.
What is the risk of natural corks?
Variability and potential TCA contamination; possible microbe ingress if poorly sealed.
How do synthetic corks perform?
Generally neutral and consistent but may allow more oxygen over time than screwcaps.
What is post-bottling refermentation?
Residual sugar + yeast + O₂ can cause unintended fermentation in bottle.
How does headspace management affect stability?
Proper CO₂ or nitrogen flushing removes O₂ that supports microbial growth.
What closures are preferred for wines with RS?
Screwcaps or tight synthetic corks to prevent yeast activation.
How do closure trials assist microbial stability?
Producers evaluate closure impact on oxygen ingress and bottle evolution to select optimal types.
