Minimising the risk

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Although previously noted (Section 8.1.4), the comment of Hammond et al. (1999) 'that the brewing process is not aseptic and the occasional chance contaminant will often be encountered' is worth reiterating. The industrial scale of the process coupled with the commercial expectations of product hygiene are such that the risk of spoilage is removed or significantly minimised by tried and tested routes.

Of these, by far the most significant vehicles for minimising risk are 'cleaning-in-place' (CiP) of vessels and mains together with downstream heat treatment (or perhaps sterile filtration) of final product. Typically, these operations are managed and 'made to happen' through quality systems that identify frequency and process validation. Outside the brewery in trade outlets, the threat of product spoilage is managed by good hygienic practices and regular 'line cleaning'.

8.2.1 In the brewery

The importance of cleaning to product wholesomeness has long been understood. Quite simply, poor hygienic practices result in poor product quality and, consequently poor sales. In other words, there is a commercial imperative to minimise the threat of microbiological contamination and product spoilage. If not a sufficient driver for good hygienic practice, legislative requirements have required breweries to adopt a significantly wider position to assuring product safety and wholesomeness (Mundy, 1997). For example, in Europe the EC Food Hygiene Directive has been implemented in the UK via the Food Safety Act which, in turn has led to an industry code by the Brewers and Licensed Retailers Association. Indeed the scope of such activities (see White, 1994) includes a number of'big themes' that together minimise (or better still remove!) chemical, physical and microbiological hazards (Table 8.7).

A key platform in meeting the broader based needs of legislation and increasingly customer demand, is the use of HACCP, an acronym for hazard analysis and critical control points. The origins of HACCP go back to the 1960s and the 'space race' - the need to ensure safe food for astronauts in space. The philosophy of HACCP - then and now - is that of a preventative strategy based on an analysis of the prevailing

Table 8.7 Rules of good hygienic practice in the brewing industry (after White, 1994).

Theme

Focus on

Details include

Personnel

Motivation, supervision, selection, training and personal hygiene

Training in basic microbiology and hygiene

Training in the principles and theory of CiP

Housekeeping and pest control

Building environment

Design criteria for internal and external areas and surfaces

Drainage, lighting, ventilation Building security, maintenance and cleanliness

Plant and equipment

Design criteria and materials of construction

Layout, operation, maintenance and cleanliness

Process control

Importance of a quality assurance system

Scope includes raw materials intake through storage to packaged product

Product

Importance that the product released to trade meets specification

Sampling and analysis plans, specifications

Legislation

Responsibilities of 'awareness' and 'compliance' to legislative requirements

Appropriate references

conditions. HACCP takes a somewhat pessimistic view in looking at what could go wrong, causes and effect and possible control mechanisms. In essence, HACCP provides a systematic framework for formally identifying potential hazards to food safety. These are assessed in terms of 'risk' and whether they are 'critical' or not. Those that are assessed as being critical are labelled as 'critical control points'. Target specifications are established for each CCP, which are then monitored to ensure the CCPs are controlled. In the event of a CCP moving out of control, corrective or remedial action is taken to bring it back in line.

HACCP analysis of the brewing process enables the chemical, physical and microbiological hazards to be broken down into bite-sized chunks (White, 1994). This enables the identification of the 'key variables', associated control points and a raft of measures for controlling the risk. Although there are pros and cons (Brown, 1997a; Jackson, 1997), HACCP is typically integrated into the brewery quality management system (typically ISO 9000) (Kennedy & Hargreaves, 1997; Mundy, 1997). Indeed, as demonstrated by Kennedy and Hargreaves (1997), there are strong links between the two (Table 8.8).

Table 8.8 Relationship between HACCP and ISO 9000 Quality System (after Kennedy and Hargreaves, 1997).

HACCP ISO 9000

Identify potential hazards, assess risk

Determine CCPs

Establish limits for control

Establish system to monitor control

Establish corrective action

Verification procedures, effective operation

Documentation and records

Management responsibility; quality system; purchasing; process control; quality planning; design control

Contract review; document and data control; external legislation; process control; purchasing; design control

Contract review; inspection and testing; document and data control; legislation; design control

Quality planning; quality system; process control; inspection and testing; inspection and test status; inspection, measuring and test equipment; handling; storage

Management responsibility; corrective and preventative action, control of non-conforming product

Inspection and tasting; internal quality audits

Document and data control; quality records

As interpreted by the brewing industry, HACCP typically focuses on chemical and physical hazards. Although there are notable exceptions (Kennedy & Hargreaves, 1997), in terms of 'due diligence' and product safety, microbiological hazards are discounted because of the widespread belief that pathogens are not present (Section 8.1.5.3). Whatever, the 'microbiological hazard' is very real when viewed in terms of product spoilage. This commercial 'risk' is controlled through sampling and testing plans (Section 8.3.1.2) and, across the process, through CiP (Section 8.2.1.1) and downstream by pasteurisation and sterile filtration (Section 8.2.2.2).

8.2.1.1 CiP and other processes. Given its importance and application across the brewing process, cleaning in place (CiP) or more generically 'cleaning' has had a bad press! As noted by Ball (1999), 'CiP is one of those basic subjects in our industry, which everyone is supposed to know about; too often people will not admit to only having a small amount of potentially prejudiced knowledge'. Although there are occasional articles in The Brewer (Barnett, 1991; Ball, 1999; Pickard, 1999) and Brewers' Guardian (Felstead, 1994), reviews on CiP in the brewing industry are few and far between. However, a good process-orientated view can be found in Celis and Dymond (1994), together with an exhaustive review of the chemistry of cleaning in Brewing Microbiology (Singh & Fisher, 1996).

Cords and Watson (1998) have identified three main drivers for cleaning and disinfection in the brewery. First, is the removal of unwanted 'soils' that could carryover and contaminate a subsequent batch of beer or wort. Second, and from the perspective of this chapter the most important, is removal of micro-organisms that could spoil or affect product consistency. Third, a factor that cannot be overlooked is the need to remove debris and soil from surfaces that impact on process performance such as wort paraflows and pasteurisers.

The nature and size of the challenge simplifies across the process from the complexity of brewhouse soils to the relative simplicity of beer prior to and during packaging (see Table 8.9). Overlaid on this is the impact of process temperature where, for example in brewhouse operations and wort cooling, soils are baked on to surfaces. Consequently, given the various demands of cleaning, there is no one universal CiP process in breweries. Indeed CiP is all about choice and choosing the best mix of options to meet the demands and constraints of cleaning. Table 8.10 identifies the major options of brewery CiP in terms of (i) choice of detergent (alkali v. acid), (ii) temperature (hot v. cold), (iii) recovery of detergent or single use and (iv) automation (manual v. automatic). Although guidelines exist for best practice, factors such as cost (capital v. revenue), complexity (small v. large brewery) and local preferences impact on choice of CiP operations. Indeed, given the evolution of cleaning practices over the last 25 years, it is common in many breweries for a mix of CiP philosophies to operate side by side.

Whatever the intricacies and choices, effective cleaning is achieved through the synergistic relationship between four parameters (Fig. 8.14) - time, temperature, chemical action and mechanical action. Manipulation of any one of these has a

Table 8.9 The changing challenge of CiP (after Cords & Watson, 1998). Location Soul composition

Brewhouse Protein, starch, minerals, beerstone, hop materials, fermentable sugars

Wort cooler/paraflow Protein, starch, minerals, beerstone, hop materials, fermentable sugars

Fermentation Protein, non-fermentable sugars, minerals, beerstone, yeast - particularly at the top and bottom of vessels

Maturation/conditioning Protein, non-fermentable sugars, minerals, beerstone, yeast

Bright beer tanks and Beerstone, foam components packaging

Table 8.10 CiP - all about choice.

Options

Guidelines and drivers

Comments

Alkaline v. Alkaline (sodium hydroxide at 2-5% acid w/v) based detergents are accepted as offering superior cleaning and greater biocidal activity than acid-based approaches. Alkaline detergents are typically used in high-soil process areas (brewhouse, fermenter and conditioning/maturation).

Acid detergents are less favoured but find application in cleaning low-soil areas such as bright beer tanks, packaging lines. A variety of acids are used including phosphoric or, more effectively, a blend of phosphoric with nitric acid.

Acid detergents are less effective detergents than caustic-based approaches. Although effective against bacteria, acid detergents have little biocidal activity with yeast (cf. acid washing).

Routinely, acid detergents have been used to periodically remove 'scale' that accumulates over time with alkaline detergents. 'Hard' water scale originates from the precipitation of calcium carbonate or magnesium hydroxide under alkaline (detergent) conditions or at high temperature. Scale protects micro-organisms from detergents and disinfectants.

Depending on the application, both alkaline and acid detergents can include surface active agents or 'surfactants' to improve the 'wetting power'. Anionic surfactants are high foaming and are used in conveyor lubricants. Non-ionic are most commonly used across the process. Cationic surfactants find application in pasteuriser water treatment. For a discussion see Singh and Fisher (1996).

Czechowski and Banner (1992) have shown caustic-based detergents to be more effective against biofilms than acid-based approaches (which were equivalent to water).

The major disadvantage of caustic-based detergent is its reaction with carbon dioxide and, to a lesser extent, water hardness salts (calcium bicarbonate, magnesium sulphate and calcium sulphate). This later reaction is minimised by the inclusion of sequestrants (e.g. sodium gluconate) in caustic detergents (Singh & Fisher, 1996).

Sodium hydroxide is highly effective at mopping-up C02 to form sodium bicarbonate, which has no significant detergent or biocidal activity. Indeed, caustic cleaning in a high C02 environment can result in vessel collapse. Depending on the COz concentration, losses of sodium hydroxide can be dramatic (Singh & Fisher, 1996). Unfortunately, as control of caustic concentration is typically through measurement of conductivity, the dilution of caustic by sodium bicarbonate is not detected and corrected by the CiP set (Barrett, 1991). Differentiation between them requires an offline titration. Gingell and Bruce (1998) report that 1 m3 (or 10 hi) COz at 1 atmosphere at 20°C will neutralise 2 kg sodium hydroxide (= 100 litres at 2% w/v). This reaction can only be minimised by removal of the C02 from the vessel, which if closed, can take many hours (Singh & Fisher, 1996). Practically, the options are to 'take the hit' and partially vent the vessel which together with the first rinse will reduce the C02 content or opt for a total dump (single use) approach, or replace with an acid detergent.

The advantages of acid-based cleaning are significant and include (i) not mopping up C02 which consequently is not 'diluted', (ii) vessels need not be vented and can be cleaned under a C02 top pressure, (iii) more easily rinsed and (iv) are used cold with consequent savings in utilities.

The poor performance of high-soil FVs and DPVs can be overcome by inclusion of an initial 'caustic pre-clean' (pre-water rinse) which removes yeast rings (Gingell & Bruce, 1988)

Table 8.10 Contd

Options

Guidelines and drivers

Comments

Hot v. cold 'If the soil goes on hot, it should be cleaned hot' (Piatt, 1986). However, high-soil areas such as yeast handling/ storage plant are typically cleaned hot.

Irrespective of detergent temperature, preclean rinses are invariably cold.

Acid detergents are typically used at ambient (cold) temperatures.

Recovery v. Full recovery systems offer savings in total dump water, heat, effluent and detergent usage. The downside is the unpredictable rate of detergent deterioration, which reduces cleaning efficacy and can lead to contamination by microbial colonisation of the recovered detergent.

Total dump or single use systems where rinse liquor and detergents are used once must provide the most effective CiP solution. However, such an approach is significantly more expensive in terms of materials and effluent.

Schematic drawings of a single-use, partial-recovery and full recovery CiP systems are presented in Figs 8.16, 8.17 and 8.18.

Automated Manual systems are resource hungry but v. manual are cheap and cheerful in terms of capital and maintenance. Process consistency is poor, as is safety. Manual systems are highly flexible.

Automated systems require little in terms of human resource but are capital hungry. Performance is typically good but they are inflexible with set routes, which can be complex to modify hardware and software. Safety is good.

Cleaning properties of detergents increases with temperature (see Fig. 8.15). Typical temperatures range from 50-90°C. There is an inevitable play-off between the improved efficacy (reduction in time and/ or detergent strength) of high temperature against the cost of heating and maintaining detergent temperature.

Single-use systems require to be close to achieve good mixing, with short mains to the tanks they are cleaning. By contrast, with recovery systems the CiP sets are remote from the tanks and the mains are long.

Total dump systems are typically used with caustic-based detergents operating in high C02 environments or in areas of gross soiling. Sodium hypochlorite can be included to enhance causticity (and therefore reduce working concentration) in freshly prepared alkaline detergents. However, care is required in temperature control and avoidance of acid (Ball, 1999).

Although less consistent, manual systems with greater human intervention, are the more 'assured'. Automatic systems, particularly those that are older or less sophisticated, have fewer 'checks and balances'. The temptation to simply press the button and initiate the clean can result in poor performance, which is assumed to have been acceptable. Periodic auditing of automatic systems is an important element of hygiene QA.

variable impact on the CiP process. Simplistically, to compensate for a reduction in detergent strength, CiP duration (time) can be extended or the temperature increased. Similarly, an increase in detergent strength or temperature can be anticipated to reduce the required cycle time. Arguably, there is less flexibility in the contribution of 'mechanical action' to the cleaning matrix. It is either right or wrong! The velocity with which the detergent and rinses are delivered is critical to the physical removal of soil (and biofilms) from surfaces. To improve shear, flow in mains must be turbulent (rather than laminar) and, in vessels, via sprayballs (fixed low pressure or rotating high pressure) to achieve coverage (Singh & Fisher, 1996). Guidelines for flow rate for mains are 1.5-2.1 msec 1 (Singh & Fisher, 1996; Ball, 1999) and for sprayballs, 1.53.5 m3h 1 for each metre of tank circumference. For tanks, which unlike mains

Time (mins)

Fig. 8.15 Impact of temperature on the concentration of sodium hydroxide (w/v) required to destroy 25% of the population of B. subtilis spores (from data reported by Singh and Fisher. 1996). Temperatures 49°C (♦). 54.5°C (■). 60°C (A). 65.5°C (•) and 71°C (*).

Time (mins)

Fig. 8.15 Impact of temperature on the concentration of sodium hydroxide (w/v) required to destroy 25% of the population of B. subtilis spores (from data reported by Singh and Fisher. 1996). Temperatures 49°C (♦). 54.5°C (■). 60°C (A). 65.5°C (•) and 71°C (*).

cannot be flooded during cleaning, it is critical that the sprayballs are configured and maintained (to avoid blockages) so that the entire vessel surface is cleaned. Where the desired flow rates cannot be achieved, the best compromise is to extend cycle time.

Inevitably, there is no such thing as a standard CiP cycle! There are, however, general principles that apply to the majority of CiP cycles (see Table 8.11). Fundamentally, CiP cycles invariably include an initial rinse, a detergent clean, and a rinse to remove detergent followed by a sterilising rinse or steam. Two factors that are

BREWING YEAST AND FERMENTATION Rinse water supply

- ^ Detergent supply

Buffer tank

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