Wut

Rinse water supply

CiP supply rA pump ^

Disinfectant # dosing pump

Day tank

Fig. 8.17 Partial recovery CiP system (redrawn from Singh and Fisher, 1996).

CiP supply rA pump ^

Disinfectant # dosing pump

Day tank

Fig. 8.17 Partial recovery CiP system (redrawn from Singh and Fisher, 1996).

Detergent supply Rinse water supply

Fig. 8.18 Full recovery CiP system (redrawn from Singh and Fisher, 1996).

Table 8.11 Typical elements of a CiP cycle.

CiP cycle step

Comments

Pre-rinse to drain

Drains/scavenge Detergent recirculation

Drains/scavenge water rinse

Drain/scavenge final rinse

Critical that the main/vessel is empty!

Critical to successful CiP and economy of detergent usage

In recovery systems the pre-rinse is recycled from the recovered rinses from the previous CiP

Pulsed or blast rinsing is frequently used in vessels to improve removal of soil

Importance can be underestimated

Critical to remove previous step prior to initiating next step

Longest part of the cycle (30-60 minutes) - efficacy determined by detergent strength, time, temperature and flow

In alkaline recovery systems detergent strength requires to be assured to account for contact with C02

In some alkaline systems, an acid 'neutralising' rinse can be included

Objective is to remove detergent

In recovery systems this rinse is recycled as the pre-rinse of the next CiP

A critical step where the entire CiP operation can be nullified by the microbiological quality of the rinse liquor

Terminal sterilents include peracetic acid, chlorine dioxide or sodium hypochlorite. The latter is being increasingly replaced because of corrosion and the threat of flavour active taints (chlorophenols and chloramines)

Wet, anaerobic steam is used in some areas of the process (packaging lines and associated vessels)

sometimes overlooked are critical to the success of any CiP cycle; first, the removal of the previous 'liquid' and, second, the microbiological quality of the intermediate and, more importantly, final rinse. Inadequate 'scavenge' of the preclean, detergent, or liquor rinses compromises the efficacy of the subsequent step and could lead to product contamination. Particular care should be taken to ensure the effective scavenge of vessels that are in the far corners of a tank farm, and consequently comparatively remote from the CiP set. The microbiological quality of liquor used in CiP can compromise and undermine the process. There is little sense rinsing a clean vessel with microbiologically contaminated water. Consequently, this risk is minimised by treatment with a disinfectant or sanitiser that kills contaminants (the various options are described in Table 8.12). An increasingly popular solution in brewing (and the wider food industry) is to treat water across a production site with chlorine dioxide. Sufficient is used to disinfect the water (and its distribution system) and to provide a 'residual' that acts on the cleaned surface. Chlorine dioxide has replaced chlorine because of growing concerns over its reactivity with organic compounds (forming flavour active taints) and its potential to corrode stainless steel. In the absence of a site-wide treatment with chlorine dioxide, final rinses are treated with the increasingly popular peracetic acid, both to kill any indigenous micro-organisms and to disinfect the cleaned surface.

Table 8.12 Disinfectants and sterilents used in brewing.

Sterilent

Mode of use

Comments

Chlorine Sodium hypochlorite (NaOCl) is typically used in breweries. Heavily influenced by pH. At alkaline pH (9-11) 97-100% is in the form of the hypochlorite ion (OCP) whereas at pH 4-6 > 97% is as 'active chlorine' or hypochlorous acid (HOC1). Compared to the hypochlorite ion, HOC1 is 20-100 times more active as a biocide. NaOCl is typically stored at pH 12 and used optimally for disinfection at pH 5.

Working concentration between 50300 mgl-1. Oxidising agent.

Chlorine Chlorine dioxide is used increasingly dioxide throughout the industry both to

'sweeten' liquor across a brewery and in CiP as a terminal disinfectant.

As an unstable gas, chlorine dioxide is typically generated at point of use. A favoured approach involves the careful mixing of hydrochloric acid with sodium chlorite solution to produce 2% C102 in water. C102 does not react with water it behaves as a 'dissolved gas'.

Used at 0.1-0.5mgl_1. Oxidising agent with potentially 2.5 x greater effect than chlorine.

Inexpensive, non-foaming but can corrode stainless steel at elevated concentrations.

Reacts with many organic compounds to form trihalomethanes, which are potential carcinogens. Also forms flavour active compounds such as chlorophenol and chloramines.

The application of C102 in the brewing industry has been reviewed by Cadwallader (1992).

Less sensitive to pH than chlorine. Does not form trihalomethanes and chlorophenols.

Strips biofilms from surfaces.

C102 must be contained. Although in widespread use there are potentially serious Health and Safety concerns which must be controlled/managed.

Table 8.12 Contd

Sterilent Mode of use Comments

Table 8.12 Contd

Sterilent Mode of use Comments

Peracetic acid (PAA)

Increasingly popular as a terminal disinfectant. Supplied as a liquid (5 or 15% PAA). In use concentration ranges from 75-300 mg L1 at ambient (or lower) temperature.

Strong oxidising agent that decomposes to form acetic acid and free radical oxygen. Wide antimicrobial activity although PAA resistant (but non-spoilage) yeasts can be selected for (e.g. Cryptococcus laurentii).

Unpleasant smell, corrosive and highly reactive. Requires careful handling and storage (transitank and bunded). Storage tanks must be vented to atmosphere as oxygen is released over time.

Effective against biofilms (Stickler, 1997).

Contact with rust should be avoided as this accelerates decomposition.

Quarternary ammonium compound ('QACs')

Although effective products, QAC

products are rarely used in CiP systems but continue to find application in soak and manual cleaning. Typically used at 200 ingC1.

Concerns that QACs are high foaming, difficult to remove by rinsing and taints ('fishy' - Barrett, 1991).

Less effective than oxidising disinfectants -resistant organisms can evolve, weak against Gram-negative bacteria.

Expensive.

Biguanides

Increasingly niche usage (soak, manual cleaning). Non-oxidising cationic polymers that reportedly disrupt microorganisms via osmotic shock. Typical in use concentration c. 600 mg L1.

Below pH 3, biguanides are ineffective and above pH 9 they are precipitated.

Safe.

Amphoterics

'Traditional' user-friendly disinfectant used manually in soak and/or spray applications. Too high foaming for CiP.

Depending on pH, ionise to produce cations, anions or zwitterions.

Non-oxidising, typically used at c. lOOOmgL1.

Safe.

On commissioning and periodically thereafter, CiP cycles should be reviewed and, where appropriate, optimised. Obviously, the success criteria include cleaning efficacy but also should include financial optimisation. CiP costs money, both directly in terms of utilities, such as CiP liquids, and indirectly in terms of time when the system is out of production. Consequently, cycle times should be considered from the perspective of time, utilities usage, detergent strength and temperature. Against this backdrop is the overriding measure of cleaning efficacy and system hygiene and microbiological performance. Clearly, there is little point in trimming a CiP cycle to reduce costs with an associated reduction in hygienic status.

Routine monitoring of CiP operations is a critical element of product and process hygiene. Despite the apparent logic of this relationship, it is fair to say that until relatively recently CiP processes frequently failed to receive the necessary process monitoring. Thankfully, things have changed! This is due in part to a greater legislative, business and systems emphasis on hygiene together with the development and industry take-up of real-time hygiene testing via ATP bioluminescence. This technology (see Section 8.3.3.1) has overcome one of the great obstacles to microbiology, historical information! Prior to the implementation of ATP bioluminescence, the hygienic status of vessels and mains was routinely assessed via conventional microbiological monitoring of surface swabs or final rinses. Unfortunately, because the nature of microbiological testing (Section 8.3.2), the results of such analyses always arrived two or three days after sampling. Such a lack of timeliness inevitably devalues the result, as it has no real process value other than tracking performance via trend analysis. Given this scenario it is no wonder that routine microbiological monitoring of CiP was viewed by many with little enthusiasm.

Real-time testing of the hygienic status of vessels and mains has facilitated a renewed commitment to validating CiP. As described in Section 8.3.3.1, ATP bioluminescence enables 'go/no go' decision making on the use of plant and enables the option of recleaning and/or further checks on CiP set-up. Although fundamentally a QC test, such real-time testing together with process checks provides a powerful vehicle for assuring CiP operations. Other checks fall into two camps - routine preclean and periodic audits. These are summarised in Table 8.13 and are reviewed by Hammond (1996). Routine preclean off-line tests include detergent strength (e.g. 'causticity' and 'carbonate') together with pH and, where appropriate, temperature. Visual checks on levels, leaks and pumps should also be included and driven by signed-off checklists. A further valuable step in the routine validation of CiP is the visual assessment of surface cleanliness post cleaning. This approach can often reveal the presence of cleaning 'shadows' that are not cleaned or missed through sprayball failure or blockage. A more sophisticated spin on this approach is to use a camera located in the top cover of the (cylindrical) vessel, which enables process events and the assessment of surface cleanliness post CiP. It is claimed that this 'TopScan' approach enables useful insight into CiP process optimisation (Wasmuht & Weinzart, 1999; see Section 6.3). Periodically the performance of CiP sets should subject to a more detailed audit where the focus is on flow rates, efficiency (microbiological and utilities) and capability. The frequency should be gauged by past history and the risk/ sensitivity of the units being cleaned. Equally, depending on performance, the

Table 8.13 Options for the monitoring of CiP operations.

CiP cycle

Sequence times Temperatures Flow rates

Detergent - causticity and carbonate v. CiP set conductivity pH

Terminal sterilent concentration

Outputs

Final rinse microbial loading

Surface (swab) microbial loading

ATP bioluminescence of final rinse sample

ATP bioluminescence of surface (swab) sample

Product microbial load measure of hygiene (ATP bioluminescence) should be extended to include conventional microbiological tests to establish the nature of the microflora and associated product risk.

8.2.1.2 Pasteurisation. Described as a 'necessary evil' (Rader, 1979), heat treatment or pasteurisation is by far the most favoured process to minimise the microbiological risk to packaged product. It should be appreciated, however, that cask and bottle conditioned products are not pasteurised and some products ('draft' beers) are made microbiologically stable through a non-thermal process, sterile filtration (see Section 8.2.1.3). With these reservations in mind, pasteurisation is globally a critically important part of the brewing process. Accordingly for a fuller view of pasteurisation than can be presented here, the reader is directed to general reviews on thermal death of brewing organisms (O'Connor-Cox et al., 1991a) and process (Huige et al., 1989; O'Connor-Cox et al., 1991b). The EBC Manual of Good Practice on Beer Pasteurisation, (European Brewery Convention, 1995) provides perhaps the definitive tome on pasteurisation with particular emphasis on engineering matters.

Ironically, although pasteurisation of beer is inevitably associated with Pasteur, the process was patented by him for the treatment of wine. Indeed, as reported by Anderson (1995), Pasteur, in his book Etudes sur la Bière, 'counsels against the pasteurisation of beer'! Although described in the EBC publication Beer Pasteurisation, Manual of Good Practice (European Brewery Convention, 1995) as a 'rather gentle heat treatment', pasteurisation does not aim for 'real' sterility. Rather pasteurisation aims to reduce microbial loading to such an extent that the product is 'commercially' sterile and, as such, is microbiologically stable. As ever, this process is a compromise between, in this case, time and temperature. The mix should achieve adequate microbial kill to assure the product's biological shelf-life but without thermal damage to product quality. To achieve both aims, the longheld view that pasteurisation provides a 'backstop' for poor upstream hygiene can no longer be acceptable. Increasingly, the commercial imperative is to reduce pasteurisation regimes and to tighten dissolved oxygen specifications to limit heat damage and to assure product freshness throughout the shelf-life.

Pasteurisation is practised in two formats, 'tunnel' and 'flash' (the latter occasionally known as 'plate'). The two processes meet different needs and differ fundamentally in duration and maximum temperature. Worldwide, tunnel pasteurisation is the most widely used to assure the commercial sterility of products packaged in can and bottle. Flash (or plate) pasteurisation is a bulk pasteurisation process used to treat beer prior to packaging in kegs or other containers that cannot be tunnel pasteurised.

Tunnel pasteurisation is a comparatively slow process through various 'zones' of fixed temperature (Fig. 8.19). The packaged product is heated in situ by spraying with increasingly hot water, held at a top temperature (e.g. 60°C) for a period of time (1020 minutes) and then cooled progressively to 10-15°C. Like CiP, the process consumes large volumes of hot water and accordingly, tunnel pasteurisers are designed to recover heat by exploiting every opportunity for heat exchange. Residence times of bottles and cans (which being more conductive require less time) in tunnel pasteurisers is lengthy, in the order of 45 minutes (Dymond, 1992). Conversely, flash

Regenerative Superheat Holding Regenerative Cooling

Heating Cooling

Regenerative Superheat Holding Regenerative Cooling

Heating Cooling

Fig. 8.19 Tunnel pasteuriser (redrawn from Beer Pasteurisation, Manual of Good Practice. EBC Technology and Engineering Forum. 1995).

pasteurisation is a rapid, almost real-time process. Here, using a plate heat exchanger (Fig. 8.20) beer is raised from 2-4°C to c. 70°C for 20-30 seconds and then rapidly cooled back to process temperature. Depending on flow rate, total residence time is typically no more than 120 seconds (Dymond, 1992).

Typically, the shelf-life of products emanating from the two processes are distinctly different. Usually homesale largepack (keg) products have a shelf-life of six to eight weeks whereas typically smallpack (cans and bottles) products have 36-52 weeks. Arguably, such differences can be related to the degree of microbiological risk associated with tunnel and plate pasteurisation which, in turn, are benchmarked against sterile filtration in Fig. 8.21. Clearly, in situ tunnel pasteurisation is potentially

Beer

Regeneration i section

Beer

Hot water circuit

Was this article helpful?

0 0
Brew Your Own Beer

Brew Your Own Beer

Discover How To Become Your Own Brew Master, With Brew Your Own Beer. It takes more than a recipe to make a great beer. Just using the right ingredients doesn't mean your beer will taste like it was meant to. Most of the time it’s the way a beer is made and served that makes it either an exceptional beer or one that gets dumped into the nearest flower pot.

Get My Free Ebook


Post a comment