Structured approach reduces production costs

Food production processes are continuously adapted under the pressure of marketing demands, the availability of new technologies, and to reduce production costs. However, poor awareness about critical aspects of new products and processes may lead to disappointing results. For example, spoiled or overprocessed products. “A structured process validation prevents such unwanted effects of adaptations and saves time, energy and money,” say experts at the Dutch research institute, TNO.

Process validation is an early and structured assessment of the process performance: how the process functions under normal and extreme conditions, and how the process is controlled. In addition, all assessment data is well-documented.

Although it might sound obvious, process validation is not common in the food industry. “In many cases, companies assume they can modify their process and save time and costs. They do not realise that by carrying out these changes, products are more likely to lose their stability and may spoil more easily. Solving these problems afterwards costs more time, money and energy than performing validation studies in advance,” says Erik Hoornstra, project leader of Microbiology at TNO Quality of Life in Zeist, The Netherlands. Process validation takes a couple of days and saves time and money-consuming trial-and-error experiments.

According to Hoornstra’s experience, smaller companies often fail to perform process validation. “They trust in turnkey delivered process lines and components. The suppliers, however, usually test their equipment at their own development centre under their standard conditions, and do not check whether the equipment fits well into the production process of their clients. It is very important to appreciate the interaction between the equipment and the product characteristics,” he emphasises.

Overprocessing

In contrast to smaller companies, large companies often do follow validation procedures. “However, these procedures are usually not appropriate for the process. Overestimating a worst-case scenario of contamination may result in ‘overprocessed’ foods, such as canned soups and sauces that have lost their taste because they have been heated for too long,” the microbiologist illustrates. Overprocessing can lead to a lower client satisfaction and consequently a lower product price.

“Better validate before than verify afterwards. And during the validation, think carefully on what process you are looking at, as every process has its own specific requirements. For example, for high pressure processing (HPP), one has to consider other microorganisms than for conventional pasteurisation methods. A structured approach makes sure you do not forget any of these aspects,” Hoornstra advises.

For more than a decade, TNO has been supporting the food industry in developing and applying a structured validation approach. The institute covers a wide range of relevant processing aspects, including microbiology, chemistry and process technology. The institute has recently validated processes such as HPP and mild preservation treatment, aseptic product packaging, and cleaning and disinfection of production plants.

Five steps

TNO uses a structured approach for validation that is based on five steps, as defined by the American Food and Drugs Administration (see FDA Info panel). In the first step, a validation plan is prepared, describing all aspects that have to be addressed. “For example, one defines the required pH and water activity of the end product; one states the storage and packaging conditions of the product; and one indicates which microorganism should be inactivated during the process,” Hoornstra explains. According to the microbiologist, the choice of these critical microorganisms is the biggest challenge of the first validation step, “For example, the acid resistance of particular microorganisms is not always clear. Therefore, at TNO, we regularly perform acid resistance tests, using our in-house bacterial strain collection. In addition, new tools using molecular microbiology are being developed for testing antimicrobial effects.”

In successive qualification steps the installation (IQ), operation (OQ), performance (PQ) and maintenance (MQ) is tested (see FDA Info panel). The well-functioning of the equipment under all – including extreme – conditions is tested. Process technologist Henk-Jan Meijer adds “During pasteurisation the coldest spot in the pasteuriser is determined using heat transfer modelling. Under these conditions, challenge tests are performed, measuring for example, the survival and growth potential of relevant microorganisms. It is our experience that, after adequate validation, adaptation of the process is seldom needed.” In case of substitution of raw materials and modifications of recipes it should be seriously considered to revalidate (change control).

Hoornstra advises all food companies to start with a structured process validation, such as the five-step plan. The microbiologist expects that process validation will become increasingly important in the near future. “New product concepts require optimised processes or novel technologies. This, together with shortening the time-to-market should not have adverse impact on product quality.” In conclusion, process validation is the way for food companies to work more efficiently and come to higher product quality.

CASE STUDY

“A food company produces several shelf-stable acid (pH < 4.0) sauces. The sauces are pasteurised for 10 minutes at 80ºC and subsequently hot-filled in cups at ~80ºC. Recently, they developed a new sauce with pH 4.5. Although the new sauce is less acid, they apply the same pasteurisation and hot-fill process. Unfortunately, the company had to recall their sauces because of spoilage.”

This is a typical example in which a more structured approach, such as the five step validation, could have prevented the recall-action. In this case the choice of the pasteurisation criterion is critical with respect to the microbial stability of the new product. There are two points in the validation process where it could have become clear the process is ineffective. Firstly, already in the validation plan a good definition of the user requirement specification should have resulted in the need to change the pasteurisation intensity: it is already known that at pH 4.5 surviving spore-forming microorganisms are capable of growing. Secondly, if this information would not have been known in advance, it would have popped up as the result of appropriate challenge tests such as described under Operation Qualification. In this case spore-forming microorganisms (“critical microorganism”) had to be added to the new product followed by the pasteurisation for 10 minutes at 80°C. The result would be spoilage of the product. The next step would involve improvement of the pasteurisation by a more intense pasteurisation (heat inactivation occurs at 10 minutes at 90°C) or change of the product formula (growth inhibition due to pH < 4.0 or the use of sorbic acid as preservative). These improvements should be tested in subsequent challenge tests. In case the equipment performs well and no growth is observed from critical microorganism, it can be concluded that the process is adequate.

FDA Information

The American Food and Drugs Administration (FDA) describes process validation as follows: ‘Establishing documented evidence which provides a high degree of assurance that a specific process will consistently produce a product meeting its predetermined specifications and quality attributes.

A structured process validation includes five steps:

1. Validation plan: description of the whole validation process, from the aim of the process and user requirement specifications (URS) to processing tools, measurement protocol, assessment criteria and documentation, time and budget.
2. Installation Qualification (IQ): assessment of correct installation and well-functioning of all essential processing- and measurement equipment. New applications have to be tested in advance (‘commissioning’), for example on temperature, pressure, pumps and valves.
3. Operational Qualification (OQ): assessment of well-functioning of all essential equipment under all conditions. In this step, process control limits – for example, based on worst case conditions – are defined. With these limits as a starting-point, challenge tests are performed.
4. Performance Qualification (PQ): assessment of well-functioning and control of the process under normal conditions, leading to a consistent product quality.
5. Maintenance Qualification (MQ): this step focuses at process control, when process indicators are exceeding their critical limits. It indicates whether a process still gives the desired outcome, even with significant changes in, for example, raw materials.’