Food Microbiology & Biotechnology

Statement 4 is NOT true: Spherical bacterial cells (cocci) have the smallest surface-area-to-volume ratio, making vegetative cocci (such as Staphylococcus aureus and Enterococcus faecalis) generally more heat-resistant than non-sporeforming vegetative rod-shaped bacteria (bacilli / rods), not less resistant. Statements 1, 2, and 3 are all biologically accurate.

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.

Molds causing black spot defects in refrigerated and frozen meats:

• Aspergillus fumigatus is a thermotolerant fungus unable to proliferate under refrigeration or frozen storage.
• Correct (Official Answer Key): Aureobasidium pullulans is the official answer designated by NTA. It is a psychrotolerant, melanin-pigmented 'black yeast' fungus capable of colonizing cold meat surfaces, resulting in distinct dark/black spot defects.
• Cladosporium herbarum is widely cited in classical food microbiology for black spot spoilage; however, Aureobasidium pullulans was selected as the key by NTA.
• Aspergillus pullulans is a non-existent taxonomic designation.