Pulp winemaking 1 Flashcards
What are 5 key features of Saccharomyces cerevisiae in winemaking?
Alcohol and sugar tolerance, SO₂ tolerance, pH/acid tolerance, temperature tolerance, anaerobic, efficiently produces ethanol.
What are general characteristics of non-Saccharomyces yeasts?
Less alcohol/sugar/SO₂ tolerant, aerobic, may produce high volatile acidity and ethanal, cannot ferment to wine alcohol levels in some cases.
How can non-Saccharomyces yeasts influence S. cerevisiae metabolism?
Through competition, provision/removal of metabolites, and release of enzymes and bioactive proteins.
What are the five key stages of yeast fermentation?
Preparing yeast, lag phase, growth phase, stationary phase, decline.
What are some worst practices in yeast preparation?
Wrong hydration temperature, using yeast too early, leaving yeast to starve, temperature shocks, chlorinated water, juice too high in sulphite.
What is the goal of starting ferments correctly?
To reach a “magic number” of cells that dominate indigenous flora.
What is direct inoculation in fermentation?
Adding commercial yeast directly to must; it’s easy but can be expensive.
What are benefits of direct inoculation with acclimatisation?
Reduces lag phase and improves yeast viability.
Why culture yeast before fermentation?
Reduces costs and improves viability.
What is a non-inoculated fermentation?
A fermentation relying on indigenous yeast without added commercial strains.
What is the purpose of adding or withholding SO₂ in non-inoculated fermentation?
To select for or against S. cerevisiae dominance.
What is cross-seeding in winemaking?
Intentional or unintentional transfer of an active fermentation to another vessel.
What is a pied de cuve?
A starter culture made by picking early and beginning fermentation in a separate vessel to seed the main batch.
Name some risks associated with improper yeast inoculation.
Fermentation failure, stuck ferments, off-aromas, contamination by spoilage microbes.
