essential Flashcards
What is yeast primarily responsible for in beer flavor?
Yeast produces many flavor-active compounds during fermentation.
What material is commonly used in the construction of fermentation systems?
Stainless steel, due to its durability, corrosion resistance, and cleanable surface.
What is flocculation in the context of yeast?
The reversible aggregation of yeast cells causing them to form clumps and either sink or rise in the fermentation medium.
Define the SHF method in bioethanol production.
Separate Hydrolysis and Fermentation, a time-consuming process that offers good control over the fermentation.
What does SSF stand for in fermentation processes?
Simultaneous Saccharification and Fermentation, combining hydrolysis and fermentation into a single process.
How does yeast contribute to the flavor of beer?
Yeast generates flavor-active compounds during fermentation that significantly impact beer’s taste.
What are cylindroconical fermenters commonly used for?
They are used extensively in brewing for their hygienic design and suitability for large batch sizes.
What is the significance of the glycolysis pathway in yeast?
Glycolysis is the primary metabolic pathway for converting glucose into pyruvate, generating energy and key metabolites.
What role do higher alcohols play in yeast metabolism?
They are involved in redox balance and possibly regulating intracellular pH.
What conditions favor the formation of esters in yeast fermentation?
Ester formation is influenced by the availability of acetyl-CoA and the fermentation conditions.
What is the Crabtree effect?
A phenomenon where high glucose levels lead to fermentation over respiration, even in the presence of oxygen.
Describe the main challenge with continuous fermentation systems.
They lack flexibility, require continuous substrate supply, and pose a high risk of microbial contamination.
How do environmental conditions affect yeast flocculation?
Influenced by factors like ion concentration, ethanol presence, and nutrient availability.
What are the key elements of an ideal fermentation system?
Includes appropriate design, efficient yeast/substrate separation, suitable capacity, hygienic construction, and effective control systems.
What is the purpose of the CIP system in fermentation?
Cleaning in Place systems facilitate the cleaning of fermentation vessels without dismantling, ensuring hygienic operations.
What does the term “flocculent” describe in yeast behavior?
It refers to the tendency of yeast to form clumps and either sink or float, which is crucial in industrial fermentations for separating yeast from the product.
How is ethanol produced during fermentation?
By converting pyruvate into acetaldehyde, which is then reduced to ethanol.
What is the main disadvantage of cylindroconical fermenters?
Potential contamination of yeast crops with non-yeast solids and issues with hydrostatic pressures that can affect yeast health.
How does stainless steel benefit fermentation vessels?
Provides excellent corrosion resistance, good cleanability, and maintains the integrity of the fermenting product.
What is the impact of oxygen on yeast fermentation?
High levels of oxygen can inhibit certain metabolic pathways in yeast, impacting flavor compound formation.
How does yeast manage environmental stress related to carbohydrate metabolism?
Yeast can convert glucose into storage carbohydrates like glycogen and trehalose, which help in stress response.
How do modern classifications of yeast flocculation vary?
Based on sensitivity to sugars such as mannose, glucose, and maltose, influencing flocculation behavior.
What is gluconeogenesis and its industrial relevance?
The reverse of glycolysis, used to metabolize non-sugar carbon sources under aerobic conditions, typically not desired in brewing.
What role does pyruvate play in yeast metabolism?
Acts as a central metabolite leading to multiple pathways, including ethanol production and amino acid synthesis.
