Statistical Process Control: What It Is and How It Drives Quality & Optimal Control in Food and Drink Manufacturing

“If you can’t describe what you are doing as a process, you don’t know what you’re doing.”

— W. Edwards Deming

Building on Shewhart’s principles, Deming advocated data-driven decision-making to reduce variation and improve overall process performance. Deming’s emphasis on structured processes and statistical methods, known as Profound Knowledge, has had a huge impact on various industries, including food and beverage manufacturing.

From raw material variability to seasonal fluctuations, food manufacturers navigate a complex production environment where maintaining consistent quality is not always straightforward. Understanding these challenges highlights why effective quality control strategies—such as SPC—are essential for reducing variability and ensuring product integrity.

Quality Challenges in Food & Beverage Manufacturing

The food and beverage industry faces unique challenges, including:

• Highly perishable products
• Variability in raw material quality and FIFO
• Diverse recipes and processing methods
• Seasonality effects and fluctuating harvesting conditions
• Smaller batch sizes compared to other industries
• More frequent product changeovers

Many manufacturers have adopted quality control and improvement techniques such as statistical process control (SPC) to maintain quality and reduce variation under these conditions. However, some still rely on manual adjustments, often overcorrecting process variations. W. Edwards Deming demonstrated that over-adjusting a process increases variation through the Funnel Experiment. If you react to every deviation by making adjustments, the process drifts further from the intended target rather than stabilising and reducing variation.

What is Statistical Process Control (SPC)?

Statistical Process Control (SPC) is a data-driven methodology for monitoring and controlling manufacturing processes to ensure consistent product quality and efficiency. Deming said ‘Bring me data. Without data you are just another person with an opinion.’

Instead of relying solely on end-product inspections, SPC focuses on real-time statistical data collection to detect variations early and prevent defects before they occur. This proactive approach helps manufacturers minimise waste and improve overall process stability.

Key SPC Concepts:

• Variability Management: Every process has variation. Where there is variation, there is waste. SPC helps differentiate between:
  • Common cause variation – inherent fluctuations within a stable process
  • Special cause variation – unexpected deviations that signal a special problem outside the established process capability
• Control Charts: Graphical tools that track process data over time, helping operators visualise trends, detect abnormalities and take corrective action before quality issues arise.
• Process Capability: A measure of the extent to which a process can consistently produce products within specification limits, ensuring efficiency and compliance with quality standards and minimal rejects.

Statistical Process Control (SPC) & Process Capability

Statistical Process Control and Process Capability are very much interrelated because both focus on understanding, controlling and improving the quality and consistency of a production process.

Process capability metrics (Cp, Cpk, Pp, Ppk) are only meaningful if the process is stable. If SPC charts show that the process is out of control (due to special causes of variation), then process capability analysis is unreliable. Hence, a strong SPC system naturally leads to better process capability, and process capability metrics can help validate how well SPC is working.

A Brewery’s Journey to Enhance Performance with SPC

A brewery recently faced challenges with manual recording of line performance and inefficiencies in identifying production losses. The paper-based method made it difficult to spot process deviations in real time. Too much overfilling and giveaway resulted in unnecessary wastage and inconsistent quality.

The brewery implemented Harford’s Statistical Process Control (SPC), Paperless Quality and OEE solutions to monitor production in real time. By capturing performance data from all production lines, including keg and cask lines, the system reduced variation and provided more precise control over the filling process, thereby reducing rejects, overfills and exposure to excess excise duty.

Using action limits based on standard deviation, the system automatically adjusted the filling process to maintain consistency and reduce waste. For any deviation beyond the limits, Harford’s system automatically encouraged a root cause analysis to identify the issue(s). Integrated with existing balances, it provided real-time feedback and automated adjustment recommendations, thereby optimising the filling processes.

Harford system helped the brewery take a proactive approach to quality control, focusing on detecting deviations early and minimising waste. Real-time control charts displayed performance data, giving operators instant feedback on production status and potential issues.

By adopting SPC, the brewery saw:

• A 0.5% reduction in giveaway and improved yield
• A 15% increase in OEE (Overall Equipment Effectiveness)
• A more data-driven, proactive approach to quality and performance management
• Better visibility and traceability

Achieving Optimal Control with Harford SPC

Harford’s system goes far beyond basic SPC by combining Statistical Process Control with Process Capability analyses, ensuring that each product, and production line, operates with the most appropriate Target and Control Limits. This precision minimises giveaway, reduces unnecessary process adjustments and helps manufacturers achieve optimal fill levels with maximum efficiency.

You can buy SPC from many companies, but at Harford, we provide more than just software—we deliver cutting-edge SPC solutions backed by expert knowledge and industry experience. That’s what makes the difference. When you are ready to learn more about our approach to optimal control and continuous improvement, please get in touch with our specialists at info@harfordcontrol.com or, better still, talk to a real person, call us on +44 (0)1225 764461.