Microbiology

Good manufacturing practice regulations of the FDA are subdivided into six categories. Name three.

Sanitation; Thermally processed, low-acid foods (packaged in hermetically sealed containers, including aseptic processing); acidified foods; cacao products and confectionery; smoked and smoke-flavored fish; frozen raw breaded shrimp

Name four toxins responsible for PSP, paralytic shellfish poisoning.

Saxitoxins are a group of more than 50 structurally related neurotoxins, including saxitoxin (STX), neosaxitoxin (neoSTX), gonyautoxins (GTX), and decarbamoylsaxitoxin (dcSTX), produced by protists, algae, and cyanobacteria.

Name 3 examples of seafood intoxications.

Scromboid poisoning, puffer fish toxin, ciguetera toxin, shellfish toxin

Explain the steps of a standard microbial plate count and how CFU/mL is calculated.

Serially dilute sample. Plate on agar medium. Incubate and count colonies (30–300 range). CFU/mL = (colonies × dilution factor) / plated volume.

List the 'Big 8' allergens in the US.

Shellfish, Fish, Milk, Eggs, Soy, Wheat, Peanuts, and Tree Nuts

What are some of the advantages of using the general method to calculate lethality?

Simple to perform, most accurate method as long as: temperature measurement is accurate, time interval is reasonable, and a proper integration method is chosen, is a good tool for process evaluation

Name 3 foods that are sources of Listeria.

Soft cheese made from unpasteurized milk, hot dogs, ready to eat deli meats, refrigerate spates or meat spreads, unpasteurized milk, refrigerated smoked seafood, raw sprouts

Name the 3 blotting techniques.

Southern - DNA; Northern - RNA; Western - protein

What are the shapes of following divisions of bacteria? cocci, bacilli, spirilla, vibrios, spirochaetes

Spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) and corkscrew (spirochaetes)

What are the two foodborne bacterial intoxications?

Staphylococcal intoxication: an enterotoxin produced by S. aureus, botulism: a neurotoxin produced by clostridium botulinum

Arrange these foodborne pathogens in the increasing order of their approximate onset time of symptoms due to infection or intoxication: Listeria monocytogenes, Staphylococcus aureus, Clostridium perfringens, and Vibrio cholerae

Staphylococcus aureus (2-4hr), Clostridium perfringens (6-12hrs), Vibrio cholerae (18-36hrs), Listeria monocytogenes (1-30 days or more)

Name two organisms responsible for foodborne illness that tolerate relatively high salt concentrations.

Staphylococcus aureus, Listeria monocytogenes.

Name 3 instrument and extensive factors that affect microorganisms growth in foods.

Temperature, water activity, pH

What are the microbial inhibitors in egg whites and how do they work?

The albumen is beneath the shell membranes and is important in providing three antimicrobial defenses to the egg. The first defense is the viscosity of the albumen components, which provide conditions in which bacteria cannot move easily. The second defense is the alkaline pH of the albumen that initially ranges from 7.6 to 7.8 but quickly increases over a period of a few days due to the loss of carbon dioxide during storage, resulting in a pH of 9.1–9.6. This is a pH range that is not conducive to the growth of most microorganisms. The third defense is the presence of a number of proteins and glycoproteins that possess antimicrobial activity: lysozyme (breaks cell walls), ovotransferrin (binds iron), and avidin (binds biotin).

Explain the significance of D-value and z-value in thermal processing.

The D-value is the time required at a specific temperature to reduce a microbial population by 90%. The z-value is the temperature change needed to change the D-value by a factor of ten. Together, they are used to design and validate thermal processes to ensure microbial safety while minimizing quality loss.

Describe the “danger zone” for bacterial growth in foods and its significance.

The temperature range of 40°F–140°F (4°C–60°C) where bacteria grow most rapidly; foods should not remain in this range for more than 2 hours to prevent foodborne illness.

A ready-to-eat refrigerated hummus product: Identify three major food safety hazards. Propose two processing or formulation controls. Suggest one packaging strategy to extend shelf life.

Three major food safety hazards: Listeria monocytogenes, Salmonella, Spoilage microorganisms (yeasts, molds) Two processing or formulation controls: Acidification (low pH), Use of preservatives (e.g., potassium sorbate), High-pressure processing, Strict sanitation and environmental monitoring One packaging strategy to extend shelf life: Modified atmosphere packaging (MAP), High-barrier packaging, Refrigerated distribution with cold-chain control

Discuss food allergens: Name the top 9 major food allergens in the U.S. Explain why cross-contact is a major concern. Describe one control measure in manufacturing.

Top 9 major food allergens in the U.S.: Milk, Eggs, Fish, Crustacean shellfish, Tree nuts, Peanuts, Wheat, Soybeans, Sesame Why cross-contact is a major concern: Even trace amounts can trigger severe allergic reactions; Can occur via shared equipment, utensils, or improper sanitation One control measure in manufacturing: Dedicated production lines; Validated cleaning procedures; Allergen labeling and employee training

Where in the US are C. botulinum type A, B, and type E generally found?

Type A: Common in the Western US (soil). Type B: Common in the Eastern/Mid-Atlantic US (soil). Type E: Common in Northern/Aquatic environments (sediment/fish).

Name the five quality grades of pork carcass.

US no. 1, US no. 2, US no. 3, US no. 4, Utility