Food Safety and Thermal Processing Exam Prep

These flashcards cover important concepts and details related to food safety, thermal processing, and related microbiological principles.

What is the pH level that defines a high acid food?

A high acid food has a pH of less than 4.6.

What organism is the target for pasteurization of low-acid products like milk?

Clostridium botulinum is NOT the target organism for milk pasteurization.

What yields the F value in thermal processes?

The area under the curve with temperature on the y-axis and time on the x-axis.

Why should low-acid canned foods be refrigerated after opening?

To prevent contamination by different bacteria, not to prevent botulism.

Does the lethal rate have units?

No, lethal rate is dimensionless.

What is the temperature tolerance of thermophilic spores during canning?

They can withstand up to 250°F for over an hour.

In a hot fill process, what is responsible for inactivating microorganisms inside the container?

The hot product itself, not a presterilized container.

Are ultra-pasteurized products shelf-stable without refrigeration?

No, ultra-pasteurized products require refrigeration.

How does the concentration of a reacting species behave in a first order reaction?

It decreases exponentially as a function of time.

What kind of organisms are associated with high decimal reduction times (D values)?

Thermally resistant organisms.

What are the units for F value and C value?

Both are measured in units of time.

How does lethal rate change with temperature?

Lethal rate decreases as temperature decreases.

What is the target organism for achieving shelf stability in low-acid products?

Clostridium botulinum.

What is the benefit of using a scraped surface heat exchanger?

It is effective for heating viscous food products.

Does steam infusion result in product dilution?

Yes, steam infusion dilutes the product.

What is the decimal reduction time (D)?

The time required for a 1-log reduction of the target microorganism at a specific temperature.

What is the z value?

The change in temperature required to achieve a 1-log reduction in the D value.

What does the Freqd value represent?

The time of processing required for a safe level of microbial inactivation at the reference temperature.

What is the F process?

The time of processing at the reference temperature that yields the same log reduction as the process in question.

If the D value is 2.6 minutes at 212°F, what is its z value?

The z value is 8°C.

What is the final microbial load if the initial load is 103 cfu/ml and is processed for 0.656 minutes?

N = 2.9 x 10^(-18) cfu/ml.

What temperature and time are used for vat pasteurization of milk?

145°F for 30 minutes.

What is a characteristic of mesophilic organisms?

They are a concern in refrigerated foods.

What is meant by the term target organism?

The microorganism that is most difficult to eliminate in a specific product.

What is a surrogate organism?

A non-pathogenic organism used to model the target organism's behavior in processes.

What factors affect the shelf life of a product?

Formulation, processing, packaging, handling, and storage.

What are common forms of deterioration in stored products?

Microbial, enzymatic, chemical, nutritional, and physical deterioration.

What is the general time and temperature for HTST pasteurization of milk?

161°F for 15 seconds.

What is the purpose of a flow diversion device in milk pasteurization?

To divert inadequately processed product back to the raw supply tank.

What is the thermal death time (TDT)?

The time required to kill a specific microorganism at a certain temperature.

What is the primary purpose of aseptic processing?

To create a sterile environment for food products.

How is a flow diversion device utilized in aseptic processing?

It is placed at the end of the cooling section.

What happens to a can containing food product processed at a high elevation when moved to sea level?

It would tend to bulge due to changes in pressure.

What does the D value indicate in food processing?

The time required at a specific temperature for a 1-log reduction in microorganisms.

What is the approximate time and temperature for canning vegetables?

250°F for 30 minutes.

How does the pressure during thermal processing affect cooked product flow?

Higher pressure on cooked product prevents raw product contamination.

What does the term F0 value represent?

The achieved lethality of a thermal process concerning rapid microbial inactivation.

Does the F value increase with higher Tref values?

No, higher Tref values result in lower F values, as indicated by the F = 10^(T−Tref)/z equation.

What is the main reason for controlling flow direction in a plate heat exchanger?

To prevent cross-contamination between raw and processed products.

What is the effect of using a thermal death time and D value?

They measure the same concept of decimal reduction, but their application can vary.

What does a 12D process involve?

It refers to a process designed to achieve a 12-log reduction in the target organism.

What needs to happen if a pinhole is formed in a plate heat exchanger?

Replace plates regularly or increase pressure on the cooked product flow.

What is the purpose of a back pressure valve in aseptic processing?

To maintain pressure and prevent product flashing after cooling.

What units are used for z value?

Degrees Celsius (°C).

What characteristic of thermophilic organisms affects their preservation during thermal processing?

Their high heat tolerance.

How does gelation during processing affect heating mode for starch-based products?

It may change from conduction to convection.

What is a challenge with effective heat transfer in viscous products?

Increased resistance to heat flow.

What is the primary microbial target for retorting low-acid products?

Clostridium botulinum.

What are intrinsic factors affecting shelf life?

Formulation and processing.

What are extrinsic factors affecting shelf life?

Packaging and storage conditions.

During pasteurization, what helps to maintain temperature?

The airspace headspace heater.

What effect does heating have on the viscosity of certain products during processing?

They can transition from convection heating to conduction heating.

What type of organisms generally exhibit higher z values?

Pathogenic bacteria.

What are the units for F process value?

Time (minutes or seconds).

What is defined as the time it takes to kill a certain amount of microorganisms at a specific temperature?

Thermal death time (TDT).

Which organism is often used as a surrogate in processing testing due to its heat resistance?

B. stearothermophilus.

What is the purpose of vacuum in processed canned foods?

To prevent can deformation during thermal processing.