FDFOP2010A
Work with temperature controlled stock
Contents
Introduction and Unit Details ………….………………………………......
4
Element 1: Store stock to meet temperature control requirements...
7
Food products requiring temperature control…………..………………..…
8
Temperature Control…………………………………………………..……....
12
Use of temperature as a control (2hr / 4 hr rule).…………………..……..
14
Use of time as a control ………………………………….……………….…..
17
Element 2: Monitor and maintain temperature of stock within specifications
Measuring temperature…………………………………………………..…….
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Cold storage……………………………………………………………..…..….
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Frozen storage ……………………….……………………………………..….
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Thawing………………………………………………………………………....
29
Food Preparation ……………………………………………………………...
31
Cooking / Thermal Processing………………..…………………………..…
33
Cooling Food …………………………………………………………………..
38
Reheating and hot holding …………………………………………………….
41
Safety Hazards …………………………………………………………………
43
Element 3. Transfer temperature controlled stock………………….….
44
Receiving food deliveries……………………………………………………..
45
Stock rotation………………………………………………………………..….
48
Activity Answers……………………………………………….………………. 49
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FDFOP2010A
Work with temperature controlled stock
Food Products Requiring Temperature
Control
Bacteria require certain environmental conditions for growth. These are
 pH
 water
 food source (protein/ sugar)
 air
 Temperature (– the temperature danger zone);
 Time (bacteria can double every 10 -20 minutes under optimal conditions)
In food production these growth parameters are used individually or in combination to
extend the shelf-life of foods and prevent the growth of pathogenic organisms. For
example:
 pH is a measure of how acid or alkaline a food is. Food spoilage and pathogenic
micro-organisms prefer a pH around 7, or neutral. By lowering the pH and making
the food more acid (say, pH 4), such as in pickled foods, microbial growth can be
hindered.

Water. Like us, micro-organisms require water or moisture to carry out their
biological functions. Remove, reduce or bind the water such as in drying or in jam
making and the microbes will be inhibited.

Air. Many, but not all micro-organisms require the oxygen in air to survive. The air
can be removed such as in tinned or vacuumed packed product. Alternatively the
oxygen can be replaced with a non-reactive gas such as nitrogen and the result is
a modified atmosphere like that used to pack potato crisps.

Food source. Obviously a bit difficult to avoid in a food product, but the removal
of food sources is important in cleaning and sanitising operations.
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Temperature. Food spoilage and pathogenic microbes prefer temperatures
between 5°C and 60°C and will have optimum growth temperatures around that
of body temperature (37°C).
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Time. Under optimum conditions, bacteria can double in numbers every 10 - 20
minutes. By altering any or all of the previous growth parameters, conditions are
no longer optimal and replication time is increased.
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FDFOP2010A
Work with temperature controlled stock
Commercial Sterilisation / UHT/ Thermal Processing
While pasteurization conditions effectively
eliminate potential pathogenic micro-organisms, it
is not sufficient to inactivate the thermo-resistant
spores. The term sterilization refers to the
complete elimination of all micro-organisms. The
food industry uses the more realistic term
"commercial sterilization"; a product is not
necessarily free of all micro-organisms, but those
that survive the sterilization process are unlikely
to grow during storage and cause product
spoilage. 1
Commercial sterilization of low-acid food is that process by which all Clostridium
botulinum spores and all other pathogenic micro-organisms are destroyed, as well as
micro-organisms which could produce spoilage under conditions of normal, nonrefrigerated storage and distribution in sealed containers. The time/ temperature
combination to achieve this is 121oC for 15 minutes.
In canning we need to ensure the "cold spot" has reached the desired temperature for
the desired time. With most canned products, there is a low rate of heat penetration to
the thermal centre. This leads to over-processing of some portions, and damage to
nutritional and sensory characteristics, especially near the walls of the container. This
implies long processing times at lower temperatures. 2
Milk can be made commercially sterile by subjecting it to temperatures in excess of 100°
C, and packaging it in air-tight containers. The milk may be packaged either before or
after sterilization. The basis of UHT, or ultra-high temperature, is the sterilization of food
before packaging, then filling into pre-sterilized containers in a sterile atmosphere. Milk
that is processed in this way using temperatures exceeding 135° C, permits a decrease
in the necessary holding time (to 2-5 s) enabling a continuous flow operation.
1
2
(Brennan, Butters, Cowell, & Lilly, 1981)
(Brennan, Butters, Cowell, & Lilly, 1981)
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Work with temperature controlled stock
Cooling Food
Chilling to temperatures below 5oC retards microbial spoilage and prevents the growth
of pathogens. The rate of biochemical changes by either micro-organisms or naturally
occurring enzymes changes rapidly with temperature. Chilling therefore reduces the rate
of enzymic and microbiological change and retards respiration of fresh foods.
Cooked potentially hazardous food that is cooled, needs to be cooled to 5°C or colder
and as quickly as possible. There may be food poisoning bacteria in the food even
though it has been cooked. Faster cooling times limit the time when these bacteria are
able to grow or form toxins.
When cooling cooked potentially hazardous food, cool the food within the following
timeframes:
 from 60°C to 21°C within two hours; and
 from 21°C to 5°C within a further four hours.3
Therefore you have a total of six hours to cool food from 60°C to 5°C or below. A probe
thermometer can be used to determine how fast the food is cooling and measure the
warmest part of the food – usually in the centre.
In a food service situation, food can be chilled quickly by breaking it up into smaller
portions in shallow containers. Take care not to contaminate the food as you do this.
Chilling Equipment
Chilling equipment is classified by the method used to remove heat:
1. mechanical refrigerators and
2. cryogenic systems
Batch or continuous operation is possible with both types of equipment
Mechanical refrigerators have four basic elements: an evaporator, a compressor a
condenser and an expansion valve. A refrigerant circulates between the four elements
of the refrigerator, changing state from liquid to gas and back to liquid. It is in the
evaporator that the liquid refrigerant evaporates and in doing so absorbs heat and cools
air, water and/or metal surfaces, which in turn cool the food.
Refrigerants commonly used are:
 Ammonia as it has excellent heat transfer properties and is not miscible4 with oil.
It is toxic, flammable and causes corrosion of copper pipes.
 Carbon dioxide is non-flammable and non-toxic, however higher operating
pressures are required.
 Halogen refrigerants (fluorine, chlorine, bromine etc) are all non-toxic and non
flammable, possesses good heat transfer properties and have lower costs than
other refrigerants. They are therefore widely used despite their miscibility with oil.
3
(FSANZ, 2013)
4
Miscible - capable of being mixed
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FDFOP2010A
Work with temperature controlled stock
Hazards
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Potentially hazardous foods delivered, purchased or transported at temperatures
between 5°C and 60°C can allow the growth of pathogenic (disease causing)
bacteria or the formation of toxins;
Food products must not be transported with chemicals as this presents a
contamination risk.
Controls and monitoring5
Only purchase goods from approved suppliers on the food business’s Approved
Suppliers list. Suppliers should also read and sign an Approved food supplier agreement
form (where they understand the temperature requirements). An employee of the
business needs to be present when the goods are delivered to carry out the following
checks:
 check that the temperature of potentially hazardous foods received from all
suppliers is 5°C or below for cold food and 60°C or above for hot food;
 check that frozen food is received frozen hard (not partially thawed);
 check that packaging isn’t damaged and that food has no immediate signs of
contamination;
 check that all products are within their ‘best before’ or ‘use by’ date;
 check that all products are properly labelled with the name and address of the
manufacturer and a batch code or a date code. A label will help you identify the
food in case it is recalled;
 ensure all deliveries are placed into designated storage areas immediately;
Corrective actions6
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5
6
reject potentially hazardous foods which are delivered having internal
temperatures between 5°C and 60°C (unless the supplier can demonstrate that
the time period at which the food has been between 5°C and 60°C will not
compromise the safety of the food).
reject products in damaged packaging;
reject goods that are incorrectly labelled i.e. no name and address of the supplier,
use by/best before date or batch code as a minimum (un-packaged food is
exempt);
reject deliveries if the inside of the delivery vehicle is unclean or is carrying
chemicals or other matter that may contaminate food;
reject suppliers that do not provide food in the agreed manner.
(Food Safety Policy and Regulation Unit - Queensland Health, 2008)
(Food Safety Policy and Regulation Unit - Queensland Health, 2008)
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