Your Answer : (Not Answered)

Correct Answer : C

The correct matching is P-4; Q-3; R-1; S-2.

• Aflatoxin is produced by the mould Aspergillus flavus (and A. parasiticus) on groundnuts and grains (4).
• Nisin is a bacteriocin produced by Lactococcus lactis and used as a food preservative (3).
• Fumonisin is a mycotoxin of Fusarium verticillioides on maize (1).
• Shiga-like toxin is produced by enterohemorrhagic E. coli such as O157:H7 (2).

The other options pair aflatoxin with Fusarium or nisin with a pathogen, which mixes up the producing organisms.

Your Answer : (Not Answered)

Correct Answer : D

Ergotism is caused by grains infected with Claviceps purpurea.

This fungus infects the flowers of rye and other cereals and replaces the grain with a hard, dark sclerotium, the ergot. Ergot contains alkaloids such as ergotamine that constrict blood vessels and act on the nervous system, causing gangrene of the limbs or convulsions and hallucinations (the medieval 'St Anthony's fire').

Clostridium perfringens is a bacterium that causes food poisoning through an enterotoxin, Rhizopus stolonifer is bread mould, and Lactococcus lactis is a harmless lactic acid bacterium used in cheese making.

Your Answer : (Not Answered)

Correct Answer : B

The Gram positive pathogen is Clostridium botulinum.

C. botulinum is a Gram positive, anaerobic, spore-forming rod. Its neurotoxin causes botulism, and its heat-resistant spores are the reason low-acid canned foods receive a full sterilizing process.

The other three are Gram negative: Campylobacter jejuni is a curved rod and a leading cause of bacterial gastroenteritis; Vibrio cholerae is a comma-shaped rod causing cholera; Salmonella typhi is the rod that causes typhoid fever.

Your Answer : (Not Answered)

Correct Answer : D

The lowest water activity is 0.86.

Staphylococcus aureus is unusually tolerant of low water activity for a bacterium. Under aerobic conditions it can grow down to about a_w 0.86, which is why it is a hazard in cured meats and other salted foods that stop most other bacteria.

0.98 and 0.91 are typical limits for many Gram-negative spoilage bacteria and for most bacteria in general, and 0.89 is above the accepted aerobic minimum for S. aureus, so none of them is the lowest value supporting its growth.

Your Answer : (Not Answered)

Correct Answer : D

The statement that is NOT correct is HACCP plan involves establishment of corrective actions as second principle.

The seven HACCP principles are: (1) conduct a hazard analysis, (2) determine the critical control points, (3) establish critical limits, (4) establish monitoring procedures, (5) establish corrective actions, (6) establish verification procedures, and (7) establish record keeping and documentation. Corrective actions are the fifth principle; the second is identifying CCPs.

The other statements are correct: HACCP is a food-safety management tool, it is preceded by five preliminary steps (team, product description, intended use, flow diagram, on-site confirmation), and it relies on prerequisite programmes such as good manufacturing practices.

Your Answer : (Not Answered)

Correct Answer : A

The order is P, R, Q, S.

The seven HACCP principles are applied in this sequence: (1) conduct a hazard analysis, (2) determine the critical control points, (3) establish critical limits, (4) establish monitoring procedures, (5) establish corrective actions, (6) establish verification procedures, and (7) establish record keeping and documentation.

Of the four listed, hazard analysis (P) comes first, then critical limits (R), then monitoring (Q), with record keeping (S) last. Monitoring cannot precede the limits it checks against, and nothing can be set up before the hazards are identified.

Your Answer : (Not Answered)

Correct Answer : C

The correct matching is P-2; Q-3; R-1; S-4.

• E. coli is a Gram-negative rod that does not form spores (2).
• Bacillus subtilis is a Gram-positive rod that forms endospores (3).
• Staphylococcus aureus is a Gram-positive coccus (round) that does not form spores (1).
• Listeria monocytogenes is a Gram-positive rod that does not form spores (4).

Option D swaps Bacillus and Listeria, the two Gram-positive rods, which differ only in spore formation. Options A and B mismatch E. coli or S. aureus.

Your Answer : (Not Answered)

Correct Answer : C

The genus without a cell wall is Mycoplasma.

Mycoplasmas have no peptidoglycan cell wall at all. Their cell membrane contains sterols, which give it some strength, and they are among the smallest free-living organisms. With no wall, they are naturally resistant to penicillin and other antibiotics that act on cell-wall synthesis, and they have no fixed shape.

Lactobacillus and Staphylococcus are Gram-positive bacteria with thick peptidoglycan walls, and Escherichia is Gram-negative, with a thin peptidoglycan layer and an outer membrane; all three have cell walls.

Your Answer : (Not Answered)

Correct Answer : C

Aflatoxins are produced by Aspergillus flavus.

Aflatoxins B1, B2, G1 and G2 are toxic, carcinogenic secondary metabolites of A. flavus and A. parasiticus, which grow on groundnuts, maize, cottonseed and tree nuts stored warm and damp. Aflatoxin B1 is among the most potent natural liver carcinogens known.

Aspergillus niger is the industrial mould used for citric acid production and is not an aflatoxin producer. Fusarium verticillioides produces fumonisins, and Rhizopus oligosporus is the mould used to ferment tempeh.

Your Answer : (Not Answered)

Correct Answer : C

The match is P-3, Q-4, R-2, S-1.

• The cytoplasmic membrane is a phospholipid bilayer with embedded proteins.
• The flagellum is the organ of motility, rotated by a motor in the cell envelope.
• The bacterial cell wall is made of peptidoglycan (murein), thick in Gram-positive and thin in Gram-negative bacteria.
• Ribosomes (70S in bacteria) carry out protein synthesis.

The other options swap these, for example giving the flagellum peptidoglycan or the cell wall motility, which are wrong.

Your Answer : (Not Answered)

Correct Answer : B

The mould is Penicillium roqueforti.

Blue-veined cheeses such as Roquefort, Gorgonzola and Stilton are inoculated with P. roqueforti. The cheese is pierced so that air reaches the interior, and the mould grows along these channels and cracks, producing blue-green sporulating veins and the characteristic flavour from its breakdown of fat.

Penicillium camemberti forms the white surface rind of Camembert and Brie, not internal veins. Rhizopus oryzae is used in fermenting tempeh and rice products, and Aspergillus niger is best known for producing citric acid; neither is a cheese mould.

Your Answer : (Not Answered)

Correct Answer : C

The product is sauerkraut.

Sauerkraut is shredded cabbage fermented with salt. Leuconostoc mesenteroides, a heterofermentative lactic acid bacterium, starts the fermentation, producing lactic and acetic acids and carbon dioxide; Lactobacillus species take over as acidity rises.

Tempeh is soybean fermented by the mould Rhizopus, natto is soybean fermented by Bacillus subtilis (natto), and miso is a soybean paste fermented with Aspergillus oryzae koji. None of them is made from cabbage.

Your Answer : (Not Answered)

Correct Answer : A

The correct match is P-3, Q-4, R-2, S-1.

• Vinegar: acetic acid bacteria such as Acetobacter aceti oxidize ethanol to acetic acid (3).
• Citric acid: industrially produced by the mould Aspergillus niger (4).
• Ethanol: brewer's and baker's yeast, Saccharomyces cerevisiae, ferments sugars to ethanol (2).
• L-Lysine: the remaining organism, the bacterium the paper prints as Enterbacter aerogenes, is paired with lysine (1).

The first three pairings are standard and are enough on their own: only one option has vinegar-3, citric acid-4 and ethanol-2. Options giving citric acid to Enterobacter or ethanol to Aspergillus reverse well-known industrial processes.

Your Answer : (Not Answered)

Correct Answer : A

The match is P-3, Q-1, R-4, S-2.

• Sake is Japanese rice wine, fermented from rice.
• Chhurpi is a traditional Himalayan cheese made from yak or cow milk.
• Natto is Japanese soybean fermented with Bacillus subtilis.
• Sauerkraut is lactic-fermented cabbage.

The other options swap rice, milk and soybean between sake, chhurpi and natto.

Your Answer : (Not Answered)

Correct Answer : C

The match is P-3, Q-4, R-2, S-1.

• Yoghurt is made with Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus.
• Cheese, in the key's pairing, with Lactobacillus casei and Streptococcus thermophilus, which are used in ripening and in many cheese starters.
• Sauerkraut is fermented by Leuconostoc mesenteroides, which starts the fermentation, followed by Lactobacillus plantarum.
• Kefir is fermented by a mixed culture that includes lactobacilli such as L. acidophilus, along with yeasts.

Yoghurt's classic pair is the decisive clue: only the options with P-3 can be right, and of those only one gives sauerkraut its Leuconostoc starter.

Your Answer : (Not Answered)

Correct Answer : C

The match is P-3, Q-4, R-2, S-1.

• Green rot of eggs is caused by Pseudomonas fluorescens, whose fluorescent pigment gives the green colour.
• Putrid swell in canned fish comes from Clostridium sporogenes, a putrefactive anaerobic spore-former that produces gas and foul odours.
• Red bread is caused by Serratia marcescens, which produces the red pigment prodigiosin.
• Yellow discoloration of meat is caused by pigmented Micrococcus species.

Each other option misplaces at least two of these organisms.

Your Answer : (Not Answered)

Correct Answer : D

The organism not responsible for ropy milk is Streptococcus lactis.

Ropiness comes from bacteria that produce slimy capsular polysaccharides in milk. Alcaligenes viscolactis is the classic cause of ropy milk, Enterobacter aerogenes also produces sliminess, and certain slime-forming strains of Streptococcus cremoris are known to cause ropiness (and are used deliberately in Scandinavian ropy milks).

Streptococcus lactis (now Lactococcus lactis) is the common lactic acid bacterium of normal milk souring; it ferments lactose to lactic acid and curdles milk, but it is not the agent of ropy fermentation.