Sterilisation Flashcards
Cosideration of heat processing setting
Heat transfer
Inactivation kinetic
Thermal death rate of the microbes
Heat processing target
Clostridium botulinium
Example of commercial sterility
in- container sterilisation
Ultra- high temperature processing
Factors influence the reaction rate
termperature pH heat efficiency types od microbes incubation conditions for the microbes food composition
Temperature influence of D- value
Increasing temp will lower the D- value
as less time is require to achieve the decimal reduction
z- value
temperature increased required to gives a 10- fold change in decimal reduction time
it indicates the thermal resistant constant of the microbes
it can be derived from the thermal resistant curve
Large z value means
the microbes has slow response the temerature change
they are more heat resisitant
F- value
Thermal death time
The time required for the microbe population reduced to stated level at given temperature
It is temp dependent
expressed as multiples of D- value
usually 12D [ process standard for low acid food (> pH 4.6)] C_0 to 10^-12 C_0.
5D [ process standard for low acid food (
Classification of food pH
> pH 4.6 = low acid
pH 4.6 = acid food
ph 2.5 - 3.7 = high acid food, such as jam
Food processing sequence
2 types of sequence and examples
Traditional sequence = first packing then process
In container sterilisation
Modern sequence = first process then packing
Aseptic processing
Stage of thermal processing [3]
Heat –> hold –> cool
Key thermal processing parameters
Temperature (heating and cooling)
Time
The time and temperature sequence depends on the purpose of treatment and the food properties
milk pasteurisation
heat to 72’C and hold for 20s –> cool rapidly to 4’C and store
Milk UHT processing
heat to 140’C and hold for 6s –> cool rapidly to 4’C and store
factors that can affect the product heating rate
product viscosity- change in starch / protein in the formulation
the filling procedures - package filling height
The rehydrationprocedures of the product
