In the laboratory, weighing is only one step in a QC analysis chain, but it strongly influences the overall quality and integrity of the final result. In production, weighing is a key factor in achieving batch uniformity and consistency in dispensing or formulation processes. Proper weighing is thus essential in ensuring continuous adherence to predefined process requirements and avoiding a frequent source of out-of-specification results.
Furthermore, accurate weighing processes help to address some of the most demanding challenges of the food industry, increasing public health, consumer safety, productivity, and competitiveness.
This article introduces a scientific methodology for selecting and testing weighing instruments within an integrated qualification approach—good weighing practices. Based primarily on the user’s weighing requirements and prevailing weighing risks, it provides a state-of-the-art strategy to reduce measurement errors and ensure reliable weighing results. Understanding weighing process requirements and important balance and scale properties such as minimum weight is essential to selecting an appropriate system. When the instrument is in use, these requirements and risks are taken into account to establish a specific routine testing scenario.
The higher the impact of inaccurate weighing and the more stringent the weighing accuracy requirements are, the more frequent testing should be. For less risky and stringent applications, however, testing efforts can be reduced accordingly. Risk and life cycle management forms an integrated part of the overall strategy of good weighing practices to bridge the gap between productivity, process quality, safety, and compliance.
OOS Results and Consequences
OOS results have always had a significant impact on consumer safety and product quality, but company productivity is also affected. OOS may result in reduced uptime due to investigations, delayed batch release, and even costly recalls. In recent years, companies are facing more stringent food safety and quality regulations. New challenges concerning food safety and quality are created by developments such as genetically modified organisms or nanotechnology. Furthermore, the rise in international sourcing and trade of food and feed are expected to accelerate this trend.
In light of these issues, along with corresponding changes in international and national laws, standards and inspection processes will be subject to regular revision. One example of recent legislation affecting the industry is FSMA, which went into effect in 2011. FSMA shifts federal regulators’ focus from responding to safety issues to preventing them. Implementation, which is still underway, will lead to enhanced prevention and increased frequency of mandatory FDA inspections. In the past, almost all FDA 483 observations and warning letters were addressed to the pharmaceutical and medical device industry; the focus is now moving toward the food industry.
Weighing is a key activity in most laboratories; however, it’s not well understood, and its complexity is often underestimated. The weighing process is even less understood in the production environment than in the lab. The selection of a scale is affected by external factors such as hygiene, ingress protection, corrosion, the risk of fire or explosion, and the health and safety of the operator. In current practices, all these factors are given higher priority than mere metrological needs. Metrological criteria—the understanding and proper consideration of which are a prerequisite for preventing OOS outcomes—are taken into consideration to an insufficient degree.
More often than not, the qualifications of production operators are lower than those of laboratory technicians. As a consequence, manipulation errors, along with OOS errors, are more frequent in production than in a laboratory.
One frequent practice is to use existing instruments for a different purpose than the one for which they were originally acquired. Unfortunately, the metrological needs of the new application may not clearly match the capability of the recycled scale.