Lager beer production — Which statement correctly describes the yeast behavior and process conditions used for lagers?

Introduction / Context:
Beer styles are differentiated by yeast species or strains and fermentation temperature. Lagers are associated with Saccharomyces pastorianus (formerly carlsbergensis), a bottom-fermenting yeast that thrives at cool temperatures and is followed by cold maturation (lagering).

Given Data / Assumptions:

• Lagers: bottom-fermenting, typically 7–13 °C primary fermentation, extended cold conditioning.
• Ales: top-fermenting, typically 18–22 °C, shorter warm maturation.
• Temperature affects ester formation, sulfur compounds, and overall flavor profile.

Concept / Approach:
Cool fermentation suppresses excessive ester and fusel alcohol formation, producing the clean profile of lagers. Yeast flocculation characteristics and fermentation kinetics also differ from ales, justifying the bottom-fermenting description historically used in breweries.

Step-by-Step Solution:

Verification / Alternative check:
Production SOPs for Pilsner, Helles, and other lagers specify cool primary fermentation with S. pastorianus and subsequent cold lagering.

Why Other Options Are Wrong:

• b/c/d: Describe ale conditions, not lager practice.
• e: Process conditions strongly influence beer style; therefore it is incorrect.

Common Pitfalls:
Assuming all beers ferment similarly; ignoring yeast strain and temperature leads to off-style results.

Final Answer:
Bottom-fermenting yeast is used for lager production at relatively cool temperatures