Various symbols have been employed to represent measured and derived variables in the applications of thermal processing science. The overall objective of these guidelines is to recommend a standard system of nomenclature for thermal processing applications. The following recommendations are to be considered voluntary guidelines. While this does not preclude the use of other symbols, these guidelines have been developed by consensus of the Institute for Thermal Processing Specialists and should be given serious consideration for adoption by individuals involved in thermal processing studies.
aw - Water activity defined as the ratio of the partial pressure of water above a food to
the water vapor pressure of pure water above a food (p) to the water vapor pressure of pure
water (po) at a given temperature (aw= p/po)
F - Time intercept from a thermal death time curve (log tgmvs T) at T = Tx
Fo - Accumulated lethality when Tx = 121.1°C (250°F) and z = 10 C° (18 F°)
pH - The degree of acidity or alkalinity of a water solution
D Value -Time in minutes at a specified temperature required to destroy 90% of microorganisms' population.
Z Value- The number of degrees Fahrenheit required for a specific bacterial thermal death time curve to pass through one log cycle.
An individual, or group, expert in the development, implementation and evaluation of thermal
and/or aseptic processes. The areas of competency listed below provide a functional
description of areas of practice, but are by no means inclusive or exclusive:
commercial equipment, and manufacturing procedures, and their effects on the delivery
of a thermal process and maintenance of product sterility;
knowledge of applicable regulations;
knowledge of the underlying principles, process calculations, analysis tools, and evaluation techniques related to thermal processing;
knowledge and understanding of the appropriate design and methods of conducting studies relating to thermal processing of food, such as: heat penetration, temperature and heat transfer distribution studies, thermal-death-time experiments, process validation and verification studies, and applying other scientific methods related to aseptic and/or thermal processing;
ability to analyze data generated by scientific studies, and evaluate the effectiveness of a thermal processing and packaging system to ensure safe and commercially sterile products;
experience and ability to identify and evaluate process deviations and spoilage incidents;
ability to document process establishment methods and results, and communicate thermal process requirements and recommendations.
Source from IFTPS Document WP.002.V1