Pickle defects – cause of blackening: In commercial pickling operations, blackening of pickles most commonly occurs due to which factor(s)?

Introduction / Context:
Dark or black discoloration is a classic quality defect in pickles. Understanding biochemical and microbiological mechanisms behind color changes helps processors prevent consumer complaints and product recalls. Two common contributors are sulfide chemistry and fungal growth.

Given Data / Assumptions:

• Certain bacteria generate hydrogen sulfide (H2S) during metabolism.
• Penicillium molds can colonize brine or surfaces when oxygen and nutrients are available.
• Plant tissues contain iron and other metals that can react with sulfide.

Concept / Approach:
H2S produced by bacteria reacts with iron to form iron sulfide (FeS), a black precipitate that stains plant tissues. In parallel, molds such as Penicillium may produce dark pigments or promote secondary reactions that discolor the product, especially in inadequately sealed or oxygen-exposed packs. Therefore, blackening frequently arises from either mechanism or their combination.

Step-by-Step Solution:
Relate H2S to iron: H2S + Fe compounds → FeS (black).Connect oxygen ingress with mold growth: surface colonization by Penicillium encourages dark patches.Assess pack conditions: poor sanitation, residual sugars, and headspace oxygen worsen both issues.Conclude that both factors are valid causes of blackening.

Verification / Alternative check:
Processors mitigate blackening by minimizing iron contamination, controlling sulfide-producing microbes via acidification, and eliminating headspace oxygen to prevent mold growth.

Why Other Options Are Wrong:

• H2S alone or mold alone may explain some cases, but both are recognized contributors.
• None of the above: contradicted by well-known spoilage pathways.
• Chlorophyll leaching: yields greenish brine, not black discoloration.

Common Pitfalls:
Ignoring trace metals; neglecting oxygen control; assuming only one microbial group is responsible.

Final Answer:
Both (a) and (b).