Sauerkraut processing: Excessively long fermentation of sauerkraut is most likely to favour the growth of which organism, leading to quality defects?

Introduction / Context:
Sauerkraut fermentation proceeds through a microbial succession: early Leuconostoc species, followed by Lactobacillus species, with heterofermentative strains potentially generating gas and off-flavours if process control lapses. Prolonged fermentation or suboptimal salt/temperature can shift dominance toward undesirable species and defects like bloating, gassiness, and soft texture.

Given Data / Assumptions:

• “Too long” a fermentation suggests extended exposure beyond optimal endpoints.
• We compare typical LAB species and a spore-former.
• We consider organisms known to cause gassy or flavour defects late in the process.

Concept / Approach:
Lactobacillus brevis is a heterofermentative lactic acid bacterium producing lactic acid, ethanol/acetate, and CO2. In prolonged fermentations, L. brevis overgrowth can increase gas formation and off-flavours. L. lactis (often referring to Lactococcus lactis) is typically early/benign in dairy contexts, and Bacillus subtilis is not favoured in acidic, saline sauerkraut conditions. Yeasts may appear on the surface but are not the principal late-holdover culprit in extended lactic fermentations at low pH.

Step-by-Step Solution:
Match “prolonged fermentation” with late-phase flora that tolerate acidity and salt. Identify heterofermentative LAB (L. brevis) as gas producers causing texture and flavour issues. Select L. brevis as the most likely overgrowing species.

Verification / Alternative check:
Fermentation guides cite L. brevis as a spoilage organism in sauerkraut and pickles when conditions extend too long or salt is low, due to gas and off-flavour production.

Why Other Options Are Wrong:

• L. lactis: Not a typical late gassy spoiler in kraut.
• B. subtilis: Spore-former that does not thrive at kraut pH and salinity.
• Saccharomyces: Surface yeasts cause scum but are less linked to late bulk over-acidification/gas in kraut.
• None of these: Incorrect because L. brevis fits the defect profile.

Common Pitfalls:
Conflating yeast surface growth with the internal heterofermentative lactic bacterial spoilage responsible for gas pockets.

Final Answer:
Lactobacillus brevis is most favoured by overly long sauerkraut fermentations and causes quality defects.