During cooking and chilling, incorporating a temperature-profiling program can help ensure HACCP compliance.

Thermal profilers measure the true product and environmental temperature in process, an essential requirement for HACCP regulations and process validation.


For years, cooking has been used to improve the quality of an array of food products. Today, food processors are increasingly supplying ready-cooked foods to add value to product and maximize market appeal. The benefits of ready-cooked meals are well documented and include improved flavor, palatability, texture and shelf life as well as reduced in-home preparation time.

The overriding benefit -- and critical requirement, in many food sectors -- of cooking remains product safety. When purchasing precooked food from the supermarket or at a restaurant, the consumer expects the food to be safe to eat. With increased public awareness, ever more visible food-poisoning outbreaks are being traced to the offending food processor. The potential outcomes -- in terms of product recall, loss of customer confidence in a food brand or supplier, and cost of litigation from affected individuals -- can be catastrophic to the profitability of a company and threaten its future market presence.

Table 1. The HACCP protocol contains seven main principles that are used to identify, control, monitor and document potential hazards in a food processing operation. To illustrate the principles, a sample application at a poultry processing plant is shown.

The HACCP Principle

Faced with market and regulatory pressures to provide safe food products, food companies worldwide are adopting hazard analysis and critical control point (HACCP) plans, either by choice or as a mandatory requirement. HACCP involves the systematic assessment of all of the main steps involved in a food operation and the identification of those steps that are critical to product safety.

The HACCP protocol contains seven main principles that are used to identify, control, monitor and document potential hazards in a food processing operation. To illustrate the principles, a sample application at a poultry processing plant is shown in table 1. In many food processing operations, often the most important critical control points within the HACCP protocol will be the cooking and chilling processes. For a poultry cooking process -- and many other food processing applications -- potentially lethal bacteria such as Listeria Monocytogenes have a critical interdependency on temperature (table 2). Getting the cook and chill processes wrong can result in a process that not only does not deliver the expected, guaranteed safe kill of bacteria but actually creates conditions where an existing contamination can be made significantly worse. There often is a fine dividing line between bacteria growth (120°F [49°C]) and bacteria kill (158°F [70°C]).

Table 2. The environmental temperature plays a role in whether a process results in bacteria growth or bacterial kill.

Putting the HACCP Plan into Practice

For many food processors, HACCP protocols now commonly are implemented. The main crux of the plan is the manual testing of food product temperatures (with a handheld thermometer) at the oven exit or during storage in a blast chiller. In itself, this action is easy to implement but does have some issues that must be managed with care. For example:
  • Does the exit temperature accurately reflect the peak product temperature?
  • Is the operator measuring the correct part of the product to test accurately?
  • Is the operator measuring products over the entire cook/oven area, including those located on the top and bottom shelves of a static food rack, or those on the left and right on a conveyor mesh belt?
  • Is manual recording of product temperature readings adequate? What risks do potential errors due to transposed readings from a digital display to quality assurance test sheet present?
In most cases, safe cooking will be ensured because the product temperature normally will peak in the oven before the quality assurance (QA) operator can access the food for measurement purposes. However, from a productivity standpoint, over-specifying the QA test temperature may be more of an issue because it may unnecessarily compromise product quality and yield.

The greatest deficiency of the use of a hand-held thermometer is that the instrument provides only a point measurement post-process. If the product’s core temperature is greater than the specified safe minimum, everything is fine and processing can continue with confidence. If the core temperature is less than the target value, major problems may exist that need to be addressed and quickly.

To obtain data that also can be used for corrective action, an oven monitoring system can be used to measure the oven and product temperature profile throughout the entire process.

Figure 1. This sample analysis shows a cook critical control point (CCP) using lethality calculations for kill of Listeria Monocytogenes. Using the entire profile data, the software calculates the FO value, or number of decimal reductions in the bacteria population. From a single number, a processor can instantaneously prove product safety. By applying alarms, potential process problems are highlighted clearly and immediately.

Temperature Profiling with a Food Monitoring System

A food monitoring system is a temperature datalogging system designed to travel with the product through the cook and chill processes, measuring the product and/or oven temperature along the way. The datalogger measures product temperature using up to eight thermocouples placed in a product or number of products located within the oven. Because the logger is located remotely from the sensing point of the thermocouple, product temperature can be measured without incurring thermal mass errors from the datalogging equipment itself. Also, the probe can be placed exactly where the measurement is required such as in the breast meat, muscle, skin or bone layer. A thermal barrier is employed to protect the datalogger from the hostile oven environment. Along with temperature protection, the barrier protects the device from water and steam. Systems are available that will even allow measurement through deep fat fryers.

After temperature data is collected, it is transferred to a PC, where the profile data can be reviewed in detail (figure 1). Using customized calculations such as peak temperature, time-at-temperature and lethality calculations FO, the critical control points of the cook and chill processes can be verified and then used to create documentary proof of HACCP compliance.

Obviously, the immediate benefit of applying temperature profiling as a means of routine HACCP protocol is that users are able to measure the true critical control point (CCP) of the product. Should trouble arise, all of the process data is available, allowing users to see where problems occurred and identify the steps necessary to correct the problems. The data also will enable users to verify the success of the corrective action.

In addition, measuring both process and product temperature eases process development, process optimization and process validation against the target CCP limits as part of the HACCP plan specification. For new product lines, the profile systems help users quickly and accurately identify the cook parameters required to achieve the desired CCP targets.

Figure 2. This example demonstrates a chill critical control point (CCP) analysis using hams in a blast chiller, post cook, as part of LACOTS (USDA) guidelines. An automatic analysis of fall times between specified target temperatures ensures that microbiological post-cook growth is prevented. Using alarm status to identify whether the process is within the CCP limits, the profiling system highlights in red those times when the CCP falls outside of the appropriate temperature, allowing immediate corrective action strategies to be employed.

Benefits without Compromising Safety

In the competitive food processing industry, with the drive to increase productivity and yields, temperature profiling provides data and information necessary to get the most out of a process without compromising safety.

Food Quality. Oven temperature monitoring can help optimize the process to maximize the food quality with regard to taste, texture and uniformity of color. It also can help prevent product recalls for cosmetic grounds or due to batch-to-batch variation.

Profitability. Oven temperature monitoring can help improve profitability by assuring food processors that their products are safe. Monitoring also allows processors to optimize the cooking temperature and time rather than adding an overcook safety contingency. If as a result of using profiling, a processor can decrease the cook temperature by 2°F or cook time by 10 percent, that processor can benefit from increased throughput and product yield per item.

Problem Solving. When process problems occur, oven monitoring systems provide a means to help engineers identify the fault and then rectify it quickly. Having the ability to react quickly limits process downtime. Engineers can use profiling data once the line is back online to prove the engineering fix has been successful.

Problem Prevention. Performing regular profile runs allows processors to understand the operating variability of their processes. Engineers can compare historical runs to identify any deterioration in performance over time, allowing processors to plan for preventive maintenance rather than react to catastrophic line failure.

Process Validation. Oven monitoring systems can be used to provide certified, traceable reports to customers as evidence of the product quality a processor provides as well as value-added process control measures undertaken to guarantee that quality.

Regular and routine temperature profiling can comprehensively satisfy all the principles of the HACCP protocol for cook or chill processes. Temperature profiling provides the means to validate processes, maximize throughput and ensure quality.

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