HEAT PENETRATION TESTS

Techniques

A heat penetration test is like a photograph.
The test measures product/container system response to heat exposure.

How to measure the progression of the heat within a container?

In order to measure the progression of the heat within a container, thermocouples such as these ones are used
 

Wireless loggers can also be used
 

How are mounted the measurements instruments?

Any of these sensors can be mounted to glass, plastic, or metal containers through appropriate receptacles

How many samples are required?

2 x 12 samples are adequate to perform a good study.
 

To insert the thermocouples into a retort

A gland is necessary to insert the thermocouples into a retort. This gland will usually be screwed in place on an elbow or a T on the vent pipe.

Plan a 2 in. dia hole.
 

I have 4 products. Do you have to test them all?

Whenever it is possible, the products are regrouped in a first test. This enables us to see which products behave the same way when exposed to heat; the number of tests required can thus be reduced.

The key question is to decide how long to heat ?

or when to cut the heat off ?

Heat is cut off when it is sufficient to allow the product to reach commercial sterility

Commercial sterility is a 2 step thermal process

2 STEP PROCESS

2nd level: spore destruction of
spoilage bacteria
(more resistant than pathogens)
2nd level: Commercial Sterility

1st level: spore destruction of pathogen bacteria
1st level: Public Health safety

 

Once the test is finished, you then get a graph as follows

Which becomes, once ground in the «mathematical mill »

Thermal process for a given set of conditions

The previous graph enables us to calculate a thermal process for a given set of conditions:

The graph on the previous page enables us to calculate a thermal process for a given set of conditions:

Product / Size Initial Temperature (C) Retort Temperature (C) Duration (Minutes)
Spaghetti Sauce, acidified, pH max 4,4;1 litre jars 60 105 D
Other

Specify heating medium; vent cycle if applicable; maximum solid fill weight if applicable; thickening agent in the formulation if applicable; viscosity of the sauce.

 

…enables also to calculate alternate processes (distinct initial temperatures)

Product / Size Initial Temperature (C) Retort Temperature (C) Duration (Minutes)
Spaghetti Sauce, acidified, pH max 4,4;1 litre jars 50 105 x
Spaghetti Sauce, acidified, pH max 4,4;1 litre jars 75 105 y
Other

Specify heating medium; vent cycle if applicable; maximum solid fill weight if applicable; thickening agent in the formulation if applicable; viscosity of the sauce.

 

…enables also to calculate alternate processes (distinct retort temperatures)

Product / Size Initial Temperature (C) Retort Temperature (C) Duration (Minutes)
Spaghetti Sauce, acidified, pH max 4,4;1 litre jars 60 100 x
Spaghetti Sauce, acidified, pH max 4,4;1 litre jars 60 110 y
Other

Specify heating medium; vent cycle if applicable; maximum solid fill weight if applicable; thickening agent in the formulation if applicable; viscosity of the sauce.

There is no duration suggested in the previous thermal process tables.

This is done purposely.

Each sauce, each formulation, would require its own heating cycle.

Using a generic process time without considering product formulation could lead to underprocessing or even food poisoning.