Pichia membranaefaciens is a well-known oxidative film-forming (pellicle-forming) yeast. In the presence of air, it grows rapidly as a white, chalky, wrinkled film/pellicle across the surface of alcoholic beverages like wine, beer, and ciders, oxidizing ethanol and organic acids into carbon dioxide and water, imparting vinegar-like off-flavors.

Aeromonas hydrophila is a psychrotrophic gram-negative aquatic rod capable of multiplying at refrigeration temperatures in dairy products. It produces lipases and amine-releasing enzymes that degrade butter lipids and lecithin into trimethylamine and volatile aldehydes, imparting an undesirable fishy off-flavor/taint (fishiness) in butter.

Microbial pathways of fish spoilage and nucleotide catabolism:

• Streptococcus cremoris (Lactococcus lactis subsp. cremoris) is a dairy lactic starter culture.
• Shewanella putrefaciens is a dominant psychrotrophic marine spoilage bacterium. It degrades post-mortem nucleotides (ATP $\to$ ADP $\to$ AMP $\to$ IMP $\to$ inosine $\to$ hypoxanthine), leading to progressive accumulation of hypoxanthine which imparts a pronounced bitter off-flavor, while also reducing TMAO to fishy TMA.
• Paraburkholderia fungorum is an environmental soil bacterium.
• While S. frigidimarina is cold-adapted, S. putrefaciens is the primary recognized spoilage agent responsible for intense hypoxanthine off-flavor.