PDA Technical Glossary
PDA Technical Reports are highly valued membership benefits because they offer expert guidance and opinions on important scientific and regulatory topics and are used as essential references by industry and regulatory authorities around the world. These reports include terms which explain the material and enhance the reader’s understanding.
The database presented here includes the glossary terms from all current technical reports. The database is searchable by keyword, topic, or by technical report. Each definition provided includes a link to the source technical report within the PDA Technical Report Portal.
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- TR 70: Cleaning/Disinfection Programs (4)
- TR 51: Biological Indicators (3)
- TR 1: Validation: Moist Heat (3)
- TR 3: Validation: Dry Heat (3)
- TR 61: Steam in Place (2)
- TR 69: Bioburden/Biofilm Management (2)
- TR 13: Environmental Monitoring (2)
- TR 54-5: Quality Risk Management for the Design, Qualification, and Operation of Manufacturing Systems (2)
- TR 45: Depth Filtration (2)
- TR 47: Virus Spikes/Virus Clearance (1)
- TR 48: Moist Heat Sterilizer Systems (1)
- TR 71: Emerging Methods for Virus Detection (1)
- TR 26: Sterilizing Filtration of Liquids (1)
- TR 29: Validation: Cleaning (1)
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D-Value
The time in minutes required for a one-logarithm, or 90%, reduction of the population of microorganisms used as a biological indicator under specified lethal conditions. For dry-heat sterilization, the D-value should always be specified with a reference temperature, DT. For example, a biological indicator (BI) challenge system with a D 160°C=1.9 minutes, requires 1.9 minutes at 160°C to reduce the population by one logarithm. (TR3) The time in minutes at a specific temperature required to reduce the population of a specific microorganism by 90% [or one (1) log] in defined conditions [e.g., method of sterilization (dry heat versus steam), solute, or carrier]. (TR13)
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D-value (D10 -Value)
The time in minutes required for a one-logarithm, or 90%, reduction of the population of microorganisms used as a biological indicator under specified lethal conditions. (TR51)
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DT Value
The time in minutes required for a onelogarithm, or 90%, reduction of the population of microorganisms used as a biological indicator under specified lethal conditions. For steam sterilization, the D-value should always be specified with a reference temperature, DT . For example, a BI system with a D121°C = 1.4 minutes requires 1.4 minutes at 121°C to reduce the population by one logarithm.(TR1) (TR61)
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Darcy Permeability
The constant of proportionality of the material as defined by Darcy’s Law. (TR45)
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De Novo Sequence Assembly
Assembly of short reads of a sequence to generate a contiguous sequence (contig). (TR71)
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Dead Leg
Area of entrapment in a vessel or piping run that could lead to contamination of the product. (TR69)
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Deadlegs
An area of entrapment in the vessel or piping run that could lead to contamination of the product due to insufficient exposure to moist heat. (TR61)
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Decontamination
A process that is designed to remove soil (including microorganisms) and may consist of cleaning and/or disinfection. (TR51)
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Depyrogenation
The destruction and/or removal of bacterial endotoxins. A depyrogenation process should demonstrate at least 99.9% or a 3-log endotoxin reduction. (TR3) Removal or destruction of pyrogens. (TR70)
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Design Reviews
Planned and systematic reviews of specifications, design, and design development and continuous improvement changes performed as appropriate throughout the lifecycle of the manufacturing system. Design reviews evaluate deliverables against standards and requirements, identify problems, and propose required corrective actions. (TR54-5)
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Design Specification
Controlled documentation that clearly and explicitly defines the manufacturing system details, codes, and standards to be followed during fabrication and construction to meet associated requirements. (TR54-5)
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Detergent
A synthetic wetting agent and emulsifier that can be added to a solvent to improve its cleaning efficiency. (TR70)
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Dirty Hold Time
The time from the end of product manufacturing until the beginning of the cleaning process (also called “soiled hold time”). (TR29)
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Disinfectant
A chemical or physical agent that reduces, destroys, or eliminates vegetative forms of harmful microorganisms but not spores. (TR70)
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Disinfection
The destruction of pathogenic and other kinds of microorganisms by thermal or chemical means. (TR51) (TR70) Process of eliminating nearly all recognized pathogenic microorganisms but not necessarily all microbial forms (e.g., bacterial spores) on inanimate objects. (TR69) The chemical or physical inactivation of a bioburden on inanimate surfaces. Typically this requires a minimum three-log (3-log) reduction of vegetative microorganisms and two-log (2-log) reduction for bacterial spore be achieved in validation. (TR13)
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Downstream Side (of Filter)
The effluent side of the process step (filter). (TR45) The filtrate or outlet side of the filter. (TR26)
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Dryness Fraction
An absolute measure of the actual latent heat of a sample of steam relative to the theoretical latent heat of saturated steam. (TR01) (TR48)
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Dryness Value
A dimensionless test quantity developed to approximate the dryness fraction. (TR01)
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Dwell Time
The period that items are subjected to a given processing condition. [Synonym: Residence Time] (TR3)
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Dynamic Light Scattering (DLS)
A technique used to measure the size and size distribution of particles. Particles suspended in a solution will cause scattering of light and the extent of the scattering is related to the size and shape of the particles. (TR47)