treatment(0.5±1%) is performedat approximately 60±70ÎC for 5 min.The
effect of chlorine-based agents can be dividedinto threephases:loosening the
biofilm fromthe surface, breakageof the biofilmand the disinfectiveeffect of
the activechlorine(Costertonet al., 1985;Wirtanen,1995).Thecleaning
solutionsshouldnot be reusedin processes aimingat totalsterility,because the
reused cleaning solutioncan contaminate the equipment (Chistiand Moo-
Young, 1994). Single-phasecleaningagentsfor CIP treatment are commonly
usedbecause the processingindustry wants to savetime(Husmark,1994). In
single-phase cleaning proceduresthe timefor one cleaningprocess,normally
the acid treatment,and a rinsing stepcan be saved. If the disinfectionis
performedusinghot water,the watershould be heatedto 90±95ÎC and the
duration should be 5 min (Bylund, 1995).
The main detergent products used in breweries are based on sodium
hydroxide. Theseagentsare highly effective in removing organic soil. The main
disadvantagein usingtheseagentsin brewerytanks is that theyreact with
carbon dioxideto forma less effectivecarbonate salt whileremoving precious
carbon dioxidefromthe process vessel(Sedgwick, 1999).Onecubicmetreof
carbon dioxideat one atmosphere and 20 ÎC will neutralise2 kg of sodium
hydroxide, whichis equivalent to 100 L of a 2% w/v solution(Gingell, 1999).
Acid-basedsanitisersare more efficientand cost effectivein removing and
preventingbeerstone and hardwater deposits (Gingell, 1999). In the tank
cleaningin breweries a CIPtechnique comprisingof an acidicstepand a
disinfecting step represents an advanced, moreeffective cleaningprocedure
undercarbondioxidepressureat low temperatures(Sedgwick, 1999).A typical
classicalacid-cleaningregimemainly usedin breweries for lightlysoiledtanks
consists of a 5±7 min pre-rinseusing recovered water, followed by 40±60min of
acid cleaning using 1.5±2.0%v/v detergent,a 5±7 min intermediate rinsewith
water, 25±30 min of acid sanitation and beerstone preventionusinga 0.5±0.6%
v/v circulation acid sanitiser and ending with a 10 min post-rinse with
microbiological purewater(Gingell, 1999).
In breweries the cleaningprocedureshouldbe basedon the oxygencontent
left in the tank aftercleaning and sanitising. Dirksen and Duca(2000)compared
acid and alkalineCIP cleaningprocedures.The procedureswerea 10 min water
rinse, 20 min acidic detergent wash,10 min waterrinseand 10 min peracetic
acid sanitiseras wellas 15 min waterrinse, 25 min alkalinedetergent wash, 10
min waterrinseand 10 min peraceticacid sanitiser respectively.They foundthat
the amount of oxygen introduced into the tank by caustic cleaning is
substantially higher than withacid cleaning. Highoxygenlevelscauseoxidation
flavouringof the beer.Furthermore, solutions of peracetic acid-based sanitisers
make onlya smalloxygencontributionto beer,if regularconcentrationand
drainage timeare observed(Vasconceloset al., 2003).A studywas madeof the
efficacyof chlorine dioxidesolutions(5±7.5ppm)as an alternative to hot water
(85 ÎC) in the disinfection step of the brewery CIP treatmentof blendingtanks,
finishingtanks and process linesundercarbon dioxide pressure,and the results
showed that chlorinedioxidecould successfully replacehot waterdisinfection.
500 Handbookof hygiene controlin the foodindustry