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Chapter 2 THERMAL PROCESSING PRINCIPLES . INFLUENCE OF ELEVATED TEMPERATURES ON MICROBIAL POPULATIONS ESTABLISHMENT OF PRODUCT SHELF LIFE AND SAFETY INFLUENCE OF THERMAL PROCESS ON PRODUCT QUALITY INTRODUCTION TO PROCESS CALCULATIONS. Vocabulary.

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chapter 2 thermal processing principles
Chapter 2 THERMAL PROCESSING PRINCIPLES
  • INFLUENCE OF ELEVATED TEMPERATURES ON MICROBIAL POPULATIONS
  • ESTABLISHMENT OF PRODUCT SHELF LIFE AND SAFETY
  • INFLUENCE OF THERMAL PROCESS ON PRODUCT QUALITY
  • INTRODUCTION TO PROCESS CALCULATIONS
vocabulary
Vocabulary
  • microbial population elevated temperature viability vegetative Salmonella spp., Listeria or Escherichiacoli-anyClostridium botulinum function of time logarithmic microbial spores abruptly semilogarithmic coordinates decimal reduction time, or D--value food spoilage microorganisms decimal reduction curve
vocabulary3
Vocabulary
  • thermal resistance curve thermal resistance constant or Z--value, thermal death time (F) survivor curve linear relationship commercial sterilization yeast and molds acidity, or pH low--acid anaerobic Low Acid Canned Food pathogen Spoilage probability quality attributes heat-sensitive nutrients flavor, texture, and color over-processing lethal rate lethality
survivor curve
survivor curve
  • When the microbial populations as a function of time are presented on semilogarithmic coordinates, a linear decrease in microbial population with time is observed. It is the survivor curve. It is emphasized that these relationships occur when the environment around the population is at a constant temperature throughout the period of exposure.
definition of decimal reduction time
Definition of Decimal Reduction Time
  • On survivor curve, the time required for a one log cycle reduction in microbial population is the decimal reduction time (D), or D--value .
thermal resistance curve
thermal Resistance Curve
  • A plot of decimal reduction time as a function of temperature on semilog coordinates results in a linear relationship. This linear relationship is the thermal resistance curve for a given microbial population.
definition of thermal resistance constant z
Definition of Thermal Resistance Constant (Z)
  • On Thermal Resistance Curve , the temperature increase required to cause a one log cycle reduction in the decimal reduction time is defined as the thermal resistance constant (Z), or Z—value.
definition of thermal death time f
Definition of Thermal Death Time (F)
  • Thermal death time (F) is defined as the time required to achieve a stated reduction in the microbial population at a given temperature (in minutes), or F--value.
relations between f d
Relations Between F & D
  • Each log cycle reduction in the microbial population on the thermal death curve represents a decimal reduction time, or D-value F--values may be expressed as multiples of D--values. The most common of these relationships is F = 12D for Clostridium botulinum in commercial sterilization.
establishment of product shelf life
Establishment of Product Shelf Life
  • Factors influence the heat resistance of microbial.
  • When product safety is concerned.
  • When product shelf life is concerned.
factors influence the heat resistance of microbial
Factors Influence the Heat Resistance of Microbial
  • Species of microorganisms.
  • Acidity or pH .
  • Oxygen (some of the spores with high thermal resistance are anaerobic).
  • Water activity
  • Food composition
when product safety is concerned
When product safety is concerned
  • The Low Acid Canned Food (LACF)
  • Food and Drug Administration
  • l2-D process for low--acid canned foods
introduction to process calculations
INTRODUCTION TO PROCESS CALCULATIONS
  • Lethal Rate Curve
  • Time/Temp. Process & LR
  • LR Curve for Thermal Process
problems
Problems
  • What is D-value, What is decimal reduction curve or survivor curve,?
  • What is Z-value, What is thermal resistance curve?
  • What is F-value, What is thermal death time curve?
  • What are the relationships between them?