There are many factors that can have an impact on the efficiency of a thermal process but one of the main considerations in the development of processes for heat preserved foods is the acquisition of accurate time/temperature profiles. The main reasons for this are:
| • | Safety – ensuring that microbial stability has been achieved and there is no risk of food poisoning or food spoilage |
| • | Optimization – reducing process times to increase production throughout and minimize energy costs |
| • | Improvement of Quality – optimization of vitamin and protein retention, and product sensorial qualities |
| • | Process Validation – providing documentation to demonstrate compliance with regulations for authorities, FDA/USDA, EC, customers, ISO9000, HACCP, etc. |
| • | Temperature Distribution – temperature mapping within a fully loaded process vessel to investigate performance against a control program and identify the cold zone |
| • | Cold Point Determination – multiple measurements within a product container to find the slowest heating point within the product (this will be product and packaging dependent) |
| • | Heat Penetration – replicate measurements with temperature measurement devices located at the position identified within the cold point tests |
The phases above are focused on identifying the worst case conditions to which a product would be exposed, with the lowest temperatures and slowest heat transfer leading to the lowest microbial reduction. It is therefore crucial that the temperature measurement devices are of high accuracy and reliability. A systematic or experimental error of 1°C in a temperature measurement system at the sterilization reference temperature of 121.1°C would lead to a corresponding error of 26% in the calculated Fo sterility value.
It is also important that the correct equipment is applied to a given validation. We have developed a large selection of probes, sensors, packing glands, and tools which are available for correct mounting in many styles and designs of containers. The range of fittings available is being continually expanded and improved with the following parameters taken into consideration:
• Correct Positioning of The Measuring Point
It is very important that the packing gland and probe are correctly positioned in the “cold spot”. If this is not obtained it can result in “false” measurements, risking high Fo/Po-values.
• Elimination of Steam and Water Ingression
It is pertinent that the packing gland and the probe are mounted so that the integrity of the container is maintained. Properly maintaining the gland will also ensure that water/steam ingression cannot reach the measuring point which would lead to false data and high Fo/Po values.
• Minimizing Risks of Heat Conduction
It is recommended that the probe and gland are mounted from the side of the container with the longest distance to the “cold spot” so that heat conduction from the water/steam is avoided. Even if the probe/gland is as small as possible and made of materials with the lowest conductivity there will always be a risk for heat conduction.
• Minimizing The Probe Assembly Inside The Container
It is very important that the probe and gland are as small as possible so that the impact on the internal environment (product) of the container, including the headspace, is minimized. This is especially important for products that receive a rotary process where the movement of the headspace will be a critical factor in the rate of heat transfer.
If it is a mixed product in liquid it is important the biggest piece of solid is positioned at the measuring point, and that the probe assembly is mounted so that it is not preventing the other solid pieces from moving freely. The reference container must be as close to the “normal” containers as possible, otherwise the heat transfer profile will no longer be a representative for the entire batch.
International
French
German