Food Processing and Thermal Dynamics Vocabulary

Vocabulary terms and definitions related to food processing, thermal inactivation, and equipment, based on lecture notes.

Low-acid food

Product with a pH greater than or equal to 4.6.

Clostridium botulinum

Target organism for canning/retorting of low-acid foods due to its lethal capacity; has mesophilic spores. Not the target organism for milk or pasteurization processes.

F value

Measure of the total lethality of a thermal process; units are time.

Lethal rate

Measure of the relative effect of temperature on microbial kill compared to a reference temperature. It does not have units. Less than 1 for temperatures below the reference temperature.

Thermophilic spores

Type of spores that are generally not destroyed in most canning/retorting operations; can withstand high temperatures for long times.

Hot fill process

Process involving filling hot product into a container, where the hot product is responsible for inactivating microorganisms on the inside of the container.

Ultra-pasteurized products

Products (like milk) treated at high temperatures but are not shelf stable and require refrigeration.

First order reaction

Reaction where the concentration of the reacting species decreases linearly with time when plotted as ln(c) vs time (as opposed to linearly with time for a zero order reaction).

High decimal reduction times (D values)

Are associated with thermally resistant organisms.

C value

Measure related to thermal processing; units are the same as F value (Time).

Decimal reduction time (D)

Time required for a 1-log reduction of the target microorganism at a specific temperature. Units are in time (e.g., minutes, seconds).

z value

Change in temperature required to get a 1-log reduction in the D value of a target microorganism. Units are in temperature (e.g., °C or °F).

F value required for a process (Freqd)

Processing time at the reference temperature needed for a process to be deemed safe based on adequate microbial inactivation. Determined by a process authority. Units are in time.

F value of a process (Fprocess)

Processing or holding time at the reference temperature that yields the same log reduction in microbial population as the actual process. Units are seconds.

Coxiella burnetti

Target organism for vat pasteurization and HTST pasteurization of whole milk.

Flow diversion device

Mechanism (often in milk pasteurization) to divert inadequately processed product back to the raw product supply tank.

Surge tank (in aseptic processing)

Tank used in aseptic processing to temporarily store sterile product (not under-processed product).

Scraped surface heat exchanger

Heat exchanger suitable for viscous products and very heat-efficient, but expensive and complex to clean.

Back pressure valve (in aseptic processing)

Valve ideally located after the cooling section in an aseptic processing system to maintain pressure and prevent flashing.

Thermal death time (TDT)

Time required at a specific temperature to kill a certain number of cells. Has units of time.

Holding tubes (inclination)

Tubes in continuous flow thermal processing systems usually inclined upward to prevent stratification and ensure proper flow monitoring.

Vat pasteurization

Milk pasteurization process at approximately 145°F for 30 minutes; kills pathogens and vegetative cells.

HTST pasteurization

Milk pasteurization process at approximately 161°F for 15 seconds; kills pathogens and vegetative cells. Target is Coxiella burnetti.

Ultrapasteurization

Milk process at approximately 280°F for 2 seconds; kills pathogens, some spoilage cells, and vegetative cells. Requires refrigeration.

Aseptic processing (milk)

Aseptic process for milk at approximately 284-285°F for 4 seconds; kills pathogens, almost all spoilage cells, and vegetative cells. Targets spoilage microbes at higher temps than HTST.

Canning/Retorting

Process at approximately 250°F for 30 minutes (variable); kills pathogens, spoilage cells, vegetative cells, and spores (e.g., 12D process for C. botulinum).

Hot-filling (high acid beverage)

Filling hot liquid (e.g., 194°F for 0.5 to 3 minutes) into a container, where the hot liquid sterilizes the container.

Helical heat exchanger

Heat exchanger offering advantages like better mixing, uniform heating, high heat transfer rate, and smaller footprint, but requires higher pumping capacity and cost.

Plate heat exchanger (pinhole prevention)

Heat exchanger where replacing plates regularly or using increased pressure on the cooked side can prevent cross-contamination through pinholes.

Gelation (of starch)

The change in heating mode from convection to conduction during retort processing of starch-based products.

Obligate anaerobes (in canned food)

Important category of microorganisms in canned food inactivation due to favorable growth in low oxygen conditions.

Mesophilic (in canned food)

Important temperature-based category of microorganisms in canned low-acid food inactivation.

Sterility of filling area (aseptic)

Maintained in aseptic packaging by laminar flow of HEPA filtered or sterile air.

Surrogate organism

Non-pathogenic microorganism similar to the target organism (e.g., similar z value) used to estimate target organism inactivation.

Factors affecting shelf life

Include intrinsic (formulation) and extrinsic (processing, packaging, handling, storage) factors.

Types of deterioration (during storage)

Include microbial, enzymatic, chemical, nutritional, physical, texture, appearance, and flavor changes during storage.

Target organism

The microorganism of concern that is most difficult to inactivate/reduce in a product (e.g., Coxiella burnetti for HTST milk, Clostridium botulinum for retorts).

Airspace/headspace heater (vat pasteurizer)

Component of a vat pasteurizer that helps maintain the foam and splash at the required temperature.