Lesson 8 - Quality Management End of Unit SAQ

***Excessively high levels of dissolved oxygen (DO₂) pick-up during filtration are an intermittent problem in your brewery. Investigations into the issue have found that the pick-up is principally due to procedural errors at operator level.

a)    Explain how by using the PDCA cycle you would make the necessary changes to the process to achieve an improvement in performance.

b)    Detail and explain the basis of the at-line and in-line equipment you could use to measure the impact of your project on DO₂ in the beer, and the laboratory method used to determine the impact of the DO₂ on the shelf life of the beer.

Response:

a) The PDCA (plan, do, check, and act) cycle enables an improvement project to be planned, executed, and embedded within the organisation, the outcomes to be established, and further improvements defined for the next PDCA cycle. The phases of the project would be as follows.

Plan Phase:

• Identify resources required to complete project and gain approval. 

• Gather information about the nature of the procedural issues.

• Establish baseline process parameters (turnaround time, operator hours/hL DP, throughput, haze, energy, and material use).

• Identify key stakeholders in the project (operators, team leaders, trainers, lab, production planning).

• Work with operators, team leaders, and technical to identify the necessary changes in procedure.

• Draft revised standard operating procedure (SOP) for task and review with stakeholders.

• Publish project plan and timeline and gain stakeholder buy-in.

Do Phase:

• Publish SOP.

• Train team leaders and operators in new procedure.

• Carry out trial using procedure.

• Adopt procedure.

• Measure process parameters for new procedure across several runs.

• Measure DO₂ in pre and post filtration.

• Determine EAP and BAX for beer post filtration.

Check Phase:

• Compare DO₂ levels with historic data.

• Compare EAP and BAX data with that from old operating procedure.

• Compare process parameters with that from old operating procedure.

• Check how procedure is working with stakeholders.

Act Phase – successful project (If DO₂, EAP, and BAX not improved stop project, return to previous procedure, and recommend further investigation):

• Ensure that all staff are trained and competent and that training records are updated.

• Set training review date.

• Update SOP in quality management system.

• Communicate change to wider business.

• Instigate next project to further improve DO₂ pick-up or other filtration process parameters.

b) There are two main methods we can use to measure DO₂ at line and in line: optochemical and the oxygen electrode. In optochemical oxygen measurement, the optical sensor is a photodetector which measures light emitted by the luminescent dye in response to stimulation by a LED light. Any oxygen in the sample absorbs some of the energy from the luminescent layer thus reducing the amount of luminescence measured by the photodetector.

In the oxygen electrode, a thin membrane which is permeable to oxygen separates the electrode from the beer. Oxygen molecules from the beer migrate across the membrane and are reduced electronically at the cathode. The electrical current produced by the flow of electrons used in this reduction is measured and used to calculate the DO₂ in the sample. Of the two methods, the optochemical is better suited to in-line measurement. The optical sensor can be cleaned and steamed in place whereas the oxygen electrodes need to be removed before hot CIP. 

In-line measurement, before and after the filter, could be used to determine the amount of DO₂ picked up through the process. Analysis of DO₂ on the CCV and BBT could also be used.

To estimate shelf life in the lab we can use oxidative resistance by electron paramagnetic resonance (EPR) spectroscopy. EPR quantifies the amount of free radicals produced by oxidation present as the beer is heated to 60 °C to accelerate aging.

To measure the free radicals, they are trapped using α-(4-Pyridyl 1-oxide)-N-tert-butylnitrone (POBN) and the concentration of the POBN free radical adduct is measured. Two values are obtained from the analysis: lag time, or endogenous antioxidative potential (EAP); and EPR intensity at 150 minutes (T150), or beverage antioxidative index (BAX). EAP, also known as lag time, is the time taken before an increase in free radicals is recorded and is a measure of resistance to oxidative damage provided by antioxidants in the beer. BAX is the level of free radicals after 150 minutes and is a guide to how rapidly the beer flavour will stale over time.

This test is only indicative of shelf life but a comparison of beers sampled from CCV and BBT before and after the change in procedure will provide a picture of the impact of the process change. Samples would of course need to be taken anaerobically.