goode 2010 food and bioproducts processing

food and bioproducts processing 8 8 ( 2 0 1 0 ) 365374

Contents lists available at ScienceDirect

Food and Bioproducts Processing

journa l homepage: www.e lsev ier .com/ locate / fbp

Chara isimpli IP

K.R. Goo leya School of C ghamb Heineken U

a

D rial p

fe e A)

te fouli

d ab sc

phases: (i) hydration and swelling, (ii) removal in the ow by dissolution and in patches and (iii) no further removal.

At 30 and 50 C water rinsing at the ow velocities investigated could remove up to 85% of the deposit. At a water

rinsing temperature of 70 C, less deposit could be removed overall. Rheological studies indicated that increasing

the temperature of the deposit generated a more elastic deposit which may decrease cleanability. Chemical cleaning

using 2wt% Advantis 210 (a NaOH base cleaning agent) eventually gave a visually clean surface at all ow velocities

a

c

5

K

1. Int

1.1. Cle

Cleaning isand beverais the ubiqstate (Tamioccur therefouling preresearch inare numeroin Fig. 1. Eaachieved atation tankcontaminaof cleaningal., 2008). A

CorresponE-mail aReceived

0960-3085/$doi:10.1016/nd temperatures. Chemical cleaning at 70 C gave the shortest cleaning times for all ow velocities, but comparable

leaning times were observed when rinsing at 30 and 50 C, suggesting that an increase in temperature from 30 to

0 C might not decrease the cleaning time.

2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

eywords: Yeast; Fermentation fouling; Water rinsing; Alkali chemical rinsing

roduction

aning yeast in brewery operations

required to avoid microbial contamination in foodge manufacture. Automated Cleaning In Place (CIP)uitous process used to return the plant to a cleanme, 2008). It can be argued that if fouling did notwould be little need for cleaning, but no economicvention method has yet been demonstrated, thusto efcient cleaning remains very important. Thereus operations involved in making beer, illustratedch stage has a level of cleanliness that needs to bend fouling is encountered at each stage. Fermen-s must be both microbiologically clean to avoidtion of the following batch and rinsed completelychemical to avoid product contamination (Salo ettypical fermenter CIP regime carried out at a brew-

ding author. Tel.: +44 (0)121 414 5451; fax: +44 (0)121 414 5324.ddress: [email protected] (P.J. Fryer).11May2010; Received in revised form13 August 2010;Accepted18August 2010

ery studied in this project is listed in Table 1. A ow velocityof at least 1.5ms1 is used. In a CIP sequence the pre-rinseand chemical phases of cleaning have the most impact on theamount of material removed.

In a brewery, yeast is used to ferment sugar extracted frommalt to make beer. This is carried out in conical fermentationvessels that hold up to 12,000 hectolitres in large scale opera-tions. Fouling deposits have been observed (Cluett, 2001) hereclassied for ease of referral as:

TypeA. Formedduring fermentationabove thebeer level. Thisdeposit can age on the surface for up to 7 days.Type B. Residual yeast attached to the vessel wall and coneduring emptying; this deposit can age on the surface for upto 5h.

Various authors have examined yeast removal from sur-faces. Yeast readily attaches to stainless steel and plastics

see front matter 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.j.fbp.2010.08.005cterising the cleaning mechancations for Cleaning In Place (C

dea,b, K. Asteriadoua, P.J. Fryera,, M. Pickshemical Engineering, University of Birmingham, Edgbaston, BirminK, 24 Broadway Park, South Gyle Edinburgh EH12 9JZ, UK

b s t r a c t

eposition of yeast inside brewery process plant is a serious indust

rmenter deposits revealed two types of fouling; yeast foam (typ

risation indicated both deposits could be mimicked in lab scale

ifferent times. Water and chemical rinsing of these deposits on a lms of yeast and the)

b, P.T. Robbinsa

B15 2TT, UK

roblem. Investigation of the cleaning of beer

and yeast lm (type B). Rheological charac-

ng experiments using yeast slurry aged for

ale ow cell revealed three distinct cleaning

366 food and bioproducts processing 8 8 ( 2 0 1 0 ) 365374

Nomenclature

AbbreviationsCAM cellulose acetate membraneCIP Cleaning In PlaceEHEDG EuropeanHygienic Engineering&DesignGroupLVR linear viscoelastic region

SymbolsC consistency of yeast slurry (wt%)cf friction factorde equivalent diameter (m)G elastic modulus (Nm2 (Pa))G viscous modulus (Nm2 (Pa))LwMyqReTavTcUVv

a

y

w50%

w

(Guillemotglass (Mercusing extetries. Guilleyeast in aatively chayeast cellsand that yewall shearfrom stainltics w50% ryeast couldsteel and aof yeast celcharge was

Fig. 1 Schematic of brewery operations (left) and thefouling typcleaning re

. Thetrin

byrem6).ingranetionuxellulosreseast w

Table 1

Stage

1

2

3

4

5

Adapted frvolume of wort (L)mass yeast slurry (g)heat ux (kWm2)Reynolds number (dimensionless)average temperature of the test sectionow (C)thermocouple (C)heat transfer coefcient (kWm2 K1)viability of yeast slurry (%)ow velocity (ms1)shear stress (s1)apparent dynamic viscosity (Nsm2)density (kgm3)the concentration of yeast slurry added to a fer-menter (g L1)wall shear stress required to remove 50% of

2

(right)more s

formedwhollyal., 200

Durmembcentralowerthe cewere pthe yeattached cells from a surface (Nm )

wall shear stress (Nm2)

et al., 2006), elastomers (Chandra et al., 2001) andier-Bonin et al., 2004) all of which are materialsnsively in the beer brewing and dispense indus-mot et al. (2006) investigated the detachment ofow chamber at a pH of 5.5, yeast cells are neg-rged over the pH range 3.57. It was found thatcould be wholly removed from glass using water,ast had a strong adhesion to stainless steel. The

stress required to remove 50% of the attached cellsess steel, denoted w50% was 30Pa, whilst for plas-anged from 1 to 2Pa. Mozes et al. (1987) found thatattach and form a dense layer of cells on stainlessluminium at pH 3 and 56, and that a dense layerls would attach to glass and plastics if the negativereduced by treatment with ferric ions. Deposits

CAM. Incremeate uxexaminedfound thatpulse pressand backpueffective inbackpulse ptive. Longeuxes. Incrhas been shand ow puing (Gillham

1.2. Ap

Until recenbeen largel

Frequently used fermenter CIP regime.

Purpose

Pre-rinse Remove bulk soil by dissolution and/or shsurface less fouled.

Chemical recirculation Circulation of alkali-based chemicals to diremaining material and kill microbes.

Intermediate rinse Circulation of water/chemical to neutralistraces of remaining chemical and materia

Sterilant Circulation of chemical/steam around theremaining microbes.

Post-sterilant rinse If necessary, sterile water rinse to removethe chemical.

om ORourke (2003).es encountered at each stage (middle). Thequirements at each stage are also indicatedcloser the process stage to nal product the

gent the level of cleaning becomes.

reaction processes or microbes usually cannot beoved with water from stainless steel (Christian et

the microltration of beer, yeast readily fouls thes. Gell et al. (1999) found that increasing the con-of yeast in solution with the protein resulted ins and intermediate protein transmission throughe acetate membrane (CAM). When the yeast cells

nt on the membrane as a layer, termed a yeast cake,as believed to form a second membrane on the

asing the thickness of this layer reduced the per-and protein transmission. Mores and Davis (2002)the effect of pulsing ow through a CAM. Theyux increased with increasing shear rate, back-ure and backpulse duration. At higher shear ratelse pressure multiple short backpulses were morecleaning the membrane. At low shear rate andressure fewer, longer backpulses were more effec-

r, weaker backpulses led to the highest recoveredeasing the ow rate or temperature of water rinsesown to aid deposit removal (Friis and Jensen, 2002),lsing has been shown to affect milk protein clean-et al., 2000).proach adopted

t years the efciency and impact of cleaning hasy neglected, as:

Conditions

ear force to leave the Ambient, 10min

ssolve and remove 70 C, 0.12wt%, 20min

e pH and removel.

Ambient, 5min

clean plant to kill Steam or ambientchemical, 15min

remaining traces of Ambient, 5min

food and bioproducts processing 8 8 ( 2 0 1 0 ) 365374 367

Fig. 2 Facfermentati

CIP is a separate

The coststantial,parametit.

There aCIP operati(energy andgas (GHG) eity. In addienables rapprocess vaowvelocittant, suchchemical cthe efcien

Identifyiby bench

Characte Measurin

ment tec

A benchery fermenRoger Bens(Benson ancost and GHwater, efutic additivepercentagestudy gavecaustic wastal impact,would be o

ignicant body of knowledge on cleaning exists withinual msatioGro

n thn (Eg inof ag ing tompion omplof dif

1 dehpas2 dein pa3 d

ovedemo

se tnt pan etcharted renn

ourrminf yed cle

Me

peritotors that contribute to the effects of beeron CIP in terms of (a) cost and (b) tonnes of CO2.

non-added value process, commonly consideredly from production, whose true cost is unknown.of brand damage from a product recall is sub-

resulting in little incentive to experiment with CIPers such as cleaning time: If it isnt broke dont x

re however numerous drivers for a revision ofons including the need to minimise utility usage

water), minimisation of waste and green housemissions, and theneed for product safety andqual-

A sindividorganiDesignlines oto cleacleaninmentcleanincleaninsemi-esicatisoil corange

typetoot

typeand

typeremfor r

ThediffereOthmalogicalpermitelled (Hbehaviin detestudy oical an

2.

The exviouslytion, the increasing use of real time microbiologyid measurement of contamination. Adjustment ofriables (temperature, time, chemical species andy) tominimise cleaning costs is increasingly impor-as moving to lower temperatures and cleaningoncentrations. This project has aimed to improvecy of fermentation CIP by:

ng CIP resource usages, costs, and CO2 emissionsmarking.rising the cleaning mechanisms.g the cleaning phenomena by in-line measure-hniques.

mark of CIP performance was carried out on brew-tation vessels. This study was designed with Prof.on based on his manufacturing benchmark toolsd McCabe, 2004). The factors that contributed toG emissions in this CIP operation were: yield loss,ent, steam, electricity, caustic, Stabilon WT (caus-), and P3 Oxysan ZS (sanitizer). Fig. 2 indicates thecontribution to (a) cost and (b) GHG emissions. Thequantitative data that indicated the use of heatedthe biggest contributor to cost and environmen-

so reducing temperature and caustic concentrationf value.

and type 3(Christian e(Cole et al.et al., 2010)and heat been usedsoil, namelcan be cleachemical clof chemicacleaning tiremoved by

2.1. For

Stainless stat the end osurfaces wered fromensured theach cleanstainless stwith a millthe test secbe fouled.(JohnSmithanufacturers, cleaning chemical companies, andns such as the European Hygienic Engineering &up (EHEDG), that has produced extensive guide-e types of surface and equipment that are easyHEDG Yearbook, 2009). Compartmentalisation offormation has resulted in independent develop-good way to clean a product. Comparison of

formation for different products and scale up ofindustrial scale equipment is thus difcult and

rical. Fryer and Asteriadou (2009) suggested a clas-f cleaning problems in terms of cleaning cost andexity, with three deposit types that represent aferent rheological and cleaning behaviours:

posit: a viscoelastic or viscoplastic uid (such aste) that can be rinsed with water alone,posit: a biological lm removed in part by waterrt by chemical, andeposit: a hard cohesive deposit that cannot beby water alone and that requires chemical actionval.

hree cleaning regimes have been investigated inrts of the ZEAL programme (see Cole et al., 2010;

al., 2010; Akhtar et al., 2010; Sahu et al., 2007). Rheo-acterisation of type 1 deposits such as yoghurt hasemoval duringwater rinsing fromapipe to bemod-ingsson et al., 2007). Knowledge of foulantmaterialunder different ow conditions is thus importanting how it can be removed from a surface. Here a

ast deposits is made to identify both their rheolog-aning behaviour.

thods and materials

mental rig used here is similar to that used pre-characterise cleaning behaviour of various type 1deposits including whey protein and tomato pastet al., 2006), egg albumin (Liu et al., 2007), toothpaste, 2010), and sweetened condensed milk (Othman. Cleaning can be quantied using image analysisux measurement. This bench top ow cell rig hashere to study the removal behaviour of a type 2y yeast deposits. The type A deposit (yeast foam)ned partially by water rinsing and completely witheaning. Here, experiments have studied the effectsl concentration, ow velocity and temperature onmes. The type B deposit (residual yeast) can bewater rinsing.

ming the deposits for cleaning

eel surfaces collected from an industrial fermenterf fermentation had variable levels of fouling. Someere only half fouled. Yeast slurry, i.e. yeast recov-fermentation was used as a fouling deposit. Thisat each test surface had 100% deposit coverage foring experiment. Deposits were formed on squareeel coupons (AISI 316) 2mm thick, 30mmby 30mmed ridge 2.5mm1mm for ease of positioning intion. This gives a surface area of 625mm2 that can1ml of yeast slurry recovered from fermentations Brewery, Tadcaster)was applied to clean coupons


Fig. 3 Sch S), acopper stu suppan ice bath le.

using a Biosamples wthe brewerwas selecteto sampleage tanks t40wt%. Thand soakedviability wtometer (NBX50, Japanwater, vorte9ml ofwateextracted awas vortexthehaemocchamber. Tcell densitiof slurry peappearancetype A dep30 C for 5 dThe percenprior to clefrom an indwere alive.was three o

2.2. Equ

The lab scacell simila(2008). A scWater waslter to thage tank wDenmark)

he sival

chemk to

ure temi, Chcontow

of 3.6ematic of the ow cell. The microfoil heat ux sensor (MHFb placed directly underneath the fouled coupon. The stub is. V manual valve, C conductivity probe, Tc thermocoup

Hit pipette (BioHit, Devon) and widened tips. Slurryere collected weekly from a yeast storage tank aty, refrigerated and used within 2 days. The tankd according to brewery records and agitated priorcollection. Slurry samples were taken from stor-hat had a total suspended solids content of up toe sample point was rinsed using de-aerated waterin Savlon spray cleaner for 5min. Cell density and

as determined prior to fouling using a haemocy-eubauer, Sussex) and light microscope (Olympus

tion. Tan equusingage tanto ensThe ch(Ecolabwhich

Therange). 1ml of yeast slurry was added to 9ml of distilledxed, and 1ml immediately extracted and added tor. This serial dilutionwas repeated oncemore, 1mlnd added to 1ml of methylene violet. The mixtureed and 20l extracted. This was pipetted betweenytometer slide and the coverslip to ll the countingypically the cell viability was greater than 90% andes were on the order of 1108 cells per ml. 650lr coupon was found to give deposits consistent in, with an average mass of 0.060.03 g. To generateosit yeast slurry was incubated on the surfaces atays, representing an industrial fermentation time.tage of live cells on the surfaces after 5 days aginganing experiments was 1%. A portion of depositustrial fermenter was assayed and 34% of the cellsThe cell density in the deposit from the fermenterrders of magnitude smaller than the yeast slurry.

ipment

le cleaning of deposits was assessed using a owr to that described by Christian (2004) and Azizhematic of the cleaning rig is illustrated in Fig. 3.directed from the mains through a reverse osmosise water or chemical tank. Water from the stor-as pumped using a centrifugal pump (Alfa Laval,through a coil in the heated tank to the test sec-

in the rangto calculataccording t

Re = vdea

wv2

= cf =

where 2 50The ow

at 20, 30, 50286035,00ow velociachieved inin industriaal. (2010). Asoil can be

Two par

The areaimages tJapan) atthe testdeterminThe deposo imagend thermocouples Tc2 and Tc3 are attached to aorted by a spring in a copper block that sits in

quare duct shaped test section was built to haveent diameter of 25mm. In cleaning experimentsicals, water was pumped from the chemical stor-the bypass loop and re-circulated back to the tank

he cleaning uid was of the desired concentration.cal used in these experiments was Advantis 210eadle). The concentrationusedwas 2wt%Advantis,ained 1wt% NaOH and 0.2wt% KOH.rates achieved through the test sectionwere in the17.0 Lmin1 (0.21.0m3 h1) giving ow velocities

1e of 0.120.6ms . The ow velocities were usede Reynolds numbers (Re) and wall shear stresseso the Blasius correlation:

(1)

0.079Re0.25 (2)

0


Table 2 ntati

Fermenta surfm2)

Industrial sPilot scale

deposit.progress

Heat traaccordin

U = qTav

from theperaturetemperattioned be

U increawhen no fube no depo

2.3. Cle

For all cleastarted rswas taken uJapan) attacFor waterfrom the wmentswatefor 30 s to pV1 (in Fig.ical tank. Oclosed andthrough tha visually cdone to remto disassem

Each expfurther depclean surfato ensure nconstant.

2.4. Rh

The ow pAR500 rheosteel parallassess thecases. Eachstage usinga minimumture trap wconstant.

2.5. Mi

As mentioncoupons. Hfouling nee

outCo.,wereupleto onfermn exte heter)e tapthyl(Talt slun gra

wy

CV

Lw i5 L),rial ft ofand

entagnd yeinima teft totatio

itiono cleters

ng lats fore o

s mathatby Cpositpreseposiouras m

ologi

Re

Rh

eoloCharacteristics of the fouling deposits formed during ferme

tion Fouling thickness(mm)

Geometryarea (

cale 3 135.0(miniature fermenter) 3 0.3

The fouled area was seen to decrease as cleaninged.nsfer coefcient, U (kWm2 K1) was determinedg to:

Tc2(3)

measured heat ux, q (kWm2), the average tem-of the test section cleaning uid (Tav), and theure of Tc2 (C), the insulated thermocouple posi-low the coupon illustrated in Fig. 3.

sed as cleaning progressed and remained constantrther deposit was removed, or there appeared tosit remaining on the surface.

aning rig procedure

ning experiments heat ux data acquisition wast. After 5 s the rst image in the series of imagessing the timer remote controller (TC-80N3, Canon,hed to the camera.After 10 s thepumpwas started.rinsing experiments the water was re-circulatedater storage tank. For chemical cleaning experi-rwas rst directed from thewater tank to the drainrove the route, ensuring the system did not leak.

3) was turned to divert the ow from the chem-nce the conductivity reading stabilised, V6 was

V7 opened. At this point chemicalwas re-circulatede chemical tank, to minimise chemical use. Whenlean surface was reached a nal water rinse wasove any chemical from the system to make it safeble in between experiments.eriment was ended 300 s after the point when noosit was seen to be removed by eye or a visuallyce was reached. The system was run to this pointo further deposit was removed and U remained

eological characterisation

roperties of yeast soils were determined using anmeter (TA Instruments, NJ, USA). The stainlessel plate geometry, 40mm in diameter, was used tosamples. A test gap of 250m** was set in mostsample was carefully applied to the centre of thea clean plastic spatula. The sample was left forof 5min to equilibrate before testing. A mois-

as used to keep the water content of the sample

carriedneliusslurryfor a cofor upof thesolutiothe plaTadcassampling meburnerof yeasFlask i

My =L

where(here 1industamounweighta percwort afor a mtray inthen lefermenIn addprior tfermena foulideposiand we

Thihopederatedthe deand retrial debehaviask wbe rhe

3.

3.1.

The rhniature fermentation system

ed in Section 2.1 yeast slurry was used to foulowever the validity of this deposit compared to realded to be tested. Pilot scale fermentations were

miniature30 C) was dFig. 4 showthe full ran

(i) signicwith thon.

ace Surface areafouled (m2)

Foulingcoverage (%)

25.45 18.90.06 20

in a miniature Cornelius Flask fermenter (The Cor-MN, USA). Typically the feedstock and the yeastadded to the vessel which is agitated or aeratedof hours. The vessel was then held at around 20 Ce week to ferment. This ask could hold up to 15 Lentation feedstock, which here was a sugar (wort)tracted from malt and sampled from the outlet ofat exchanger at the brewery (John Smiths Brewery,when it was en route to a fermentation vessel. Thewas sterilised before and after sampling by spray-ated spirit and aming using a portable bunsenentum Development Ltd., Lancashire). The massrry (My) required for fermentation in the Corneliusms was determined from:

(4)

s the volume of wort added to the ask in litresy is the concentration of yeast slurry added to theermenter (here 7 g L1), C is the consistency, thesuspended solids as a percentage of the mixtureV is the viability, the fraction of live yeast cells ase of the volume of the mixture. Upon addition ofast to the Cornelius ask, it was agitated on a stageum of 2h before being positioned on a plastic drip

mperature controlled room at 20 C. The ask wasferment for 5 days, representative of an averagen time, and the fouling layerswere then inspected.

, industrial fermenters at the brewery were openedaning and the fouling layers observed. Industrialand the miniature fermentation systems showedyer above the beer level that looked similar. Bothuled a similar amount of the vessel surface areaf a similar thickness, summarised in Table 2.terial was sampled and its rheology tested. It wasthe rheological characterisation of the deposit gen-ornelius ask fermentation would resemble that ofgenerated in the industrial fermenter. Substantialntative rheological characterisation of the indus-t was not feasible but limited tests to assess owcould be carried out. Deposit from the Corneliusore readily available, easier to handle and could

cally characterised more easily.

sults and discussion

eological characterisation

gical behaviour of the industrial deposit (at 30 C),fermenter deposit (at 25 C) and yeast slurry (at

etermined by shear sweeps from 0.01 to 1000 s1.s the apparent viscosity of the three materials overge of shear rates tested. The three deposits show:

antly different behaviour at low shear rates,


Fig. 4 Viscosity vs. shear rate plot of industrial type Adeposit (at 30 C), miniature fermenter deposit (at 25 C),and yeast slurry (at 30 C).

factor of 10 than that from the pilot fermenter, and theyeast slurry having a viscosity a factor of ten less;

(ii) in the range >2 s1, the three materials show similar,shear-thinning behaviour. Here the industrial deposit hasa lower viscosity.

(iii) at higher shear rates, >100 s1, the three again diverge.

From the data it is clear that the industrial deposit hasthe highest viscosity at low shear, followed by the pilot scaledeposit, then the yeast slurry. This may reect the length oftime the deposit was aged on the surface which for the indus-trial deposit was at least 141h, pilot slurry at least 72h, andyeast slurry for 1h. The longer the deposit was aged on thesurface the more solid it became. This was also observed by

Mercier-Bonin et al. (2004) who discovered the longer yeastcells were left to contact a glass surface the more strongly thecells were attached.

All deposits demonstrated shear-thinning behaviour. Theyeast slurry was seen to commence shear-thinning behaviourat a much larger shear rate than the miniature fermenterdeposit, around 7 s1. This was due to the yeast slurry sam-ple retaining liquid. These ndings suggest that higher owrates would be needed to clean the deposit after a long periodof ageing on the surface unless chemical is added to disruptthe deposit structure.

Oscillatory stress sweeps of the miniature fermenterdeposit and the yeast slurry were conducted at temperaturesbelow 20 C in the range of 0.01 to >100Pa, illustrated inFig. 5(a) and (b). The two sets of curves have similar shapes,with G >G at low stress and G =G at higher stress. Thecrossover point was found to be at 5.5 Pa for the pilot scaledeposit and 1.5 Pa for the yeast slurry. It is notable that themagnitude of the low shear modulus is much greater for thefermenter deposit, at 500Pa as opposed to 140Pa at an oscil-latory stress of 0.1 Pa. This is most likely due to differenttesting temperatures; 15 C for miniature fermenter depositand 18 C for yeast slurry. The maximum surface shear stressachieved in this cleaning system was 1.24 Pa (estimated fromEq. (2)) suggesting the deposits would probably remain pre-dominantly elastic over the ow velocities and temperaturesinvestigated.

An oscillatory stress of 0.5 Pawas selected for further inves-tigation of the linear viscoelastic region (LVR) of both deposits.Fig. 5(c) and (d) illustrate that G remained greater than G forboth deposits when the temperature was ramped from 20 to70 C. Increasing the temperature also increased the magni-

Fig. 5 (a)at 18 C, (c)0.5 Pa.Oscillatory stress sweeps of the miniature fermenter deposit at 1temperature ramp of the miniature fermenter deposit, and (d) te5 C, (b) Oscillatory stress sweep of yeast slurrymperature ramp of yeast slurry, stress amplitude


tude of the measured modulus, more so for the pilot scaledeposit thato the gelatin the maggreater mocal behavioyeast slurryif the aging

3.2. De

At the tempand chemicbe characte

I. Depositlighter

II. Depositpatches

III. No furtwas rea

In all casstate visuaby furthertrated in FigA sectionreectanceto be cluste

Fig. 7 ilexperimenand chemicdescribed aeach proleduration ofther deposremoves althe duratio

3.3. Th

At all t(0.260.5mdeposit onerosion atdeposit wabecame lighillustrate thing rinsinglarge patchremoved mshows that

Temperaow velotrend atclear diff

there is aperaturestarts, wquickly.

rinsing atime.

(a) A typical coupon showing that the surface is notly clean. A section of this coupon surface is shown inthe surface using a surface reectance microscope.ast cells are green and the surface is yellow. Theit was yeast slurry. (For interpretation of theces to colour in this gure legend, the reader isd to the web version of the article.)

at 70 C is most scattered, there is some evidence thatt signicant removal is found at the highest velocity,ever there is less removal than at 50 C.

ological studies indicated that increasing the tempera-the deposit generated amore elastic deposit, illustrated5(b) and (d). Thismayhave resulted in a deposit thatwassusceptible to deformation by the ow. An increase inelocity, or the addition of chemical to the ow woulduired to remove any more deposit. Water penetratione deposit whilst rinsing with water appears optimal atTo remove deposit most quickly and use less water ining the deposit a rinse temperature of 50 C would beted from these results. With a more successful waterhere would be a reduced deposit load in the chemicalg phase,whichwould help to reduce cleaning chemicald potentially the temperature of the clean.

The effect of chemical

e taken to remove the type A deposit was determinedach series of images, and is displayed in Fig. 9. For eachn the yeast slurry. This effect may have been dueion of proteins within the deposits. The differencenitude of the modulus was also expected due toisture retention in yeast slurry. Similar rheologi-ur was shared by the two deposits, indicating thatcould be used to mimic industrial fouling deposittime was increased.

posit removal proles

eratures and ow velocities investigated for wateral rinsing, three phases were identied that couldrised by U and area proles:

hydration and swelling; the deposit becamein colour.removal by uid ow in part by dissolution and in.her removal of deposit; or a visually clean surfaceched.

es ofwater rinsing the surfacedidnot reacha cleanlly; an adhesive lm that could not be removedwater rinsing remained. A typical coupon is illus-. 6(a) showing that the surface is not visually clean.

of this coupon surface obtained using a surfacemicroscope is shown in Fig. 6(b). The lmappearedrs of yeast cells (in green) on the surface (in yellow).lustrates U and area proles of deposit removalts conducted at a ow velocity of 0.5ms1 forwateral rinsing at ambient andat 70 C. The three phasesbove are separated by the vertical dashed lines in. Increasing the temperature decreased both thethe swelling phase and the time at which no fur-

it removal occurs. The use of 2wt% Advantis 210l deposit to a visually clean surface, and reducedn of the initial swelling phase at all temperatures.

e effect of mechanical ow and temperature

emperatures (2070 C) and ow velocitiess1), as the rinsing time increased the amount ofthe coupon decreased. There was some depositthe coupon edges and the majority of type As removed in patches in the ow. The depositter in colour as rinsing time increased. Fig. 8(a)(c)e change in the average deposit area with increas-time at 20, 30, 50, and 70 C. In all cases, initiallyes of deposit were removed, but the size of theaterial decreased with time. Overall the data

:

ture has a bigger impact on deposit removal thancity, in that most of the velocity data shows noeach temperature, except at 70 C where there is aerence in rinsing at 0.26 and 0.5ms1.clear difference between 20 C and the other tem-

s, with a lengthy period (ca. 400 s) before removalhilst at other temperatures removal starts more

t 50 C removed the most deposit in the shortest

Fig. 6 visual(b) onThe yedeposreferenreferre

datamoshow

Rheture ofin Fig.not soow vbe reqinto th50 C.removsuggesrinse tcleaninuse an

3.4.

The timfrom e


Fig. 7 Removal proles of U and area for type A deposit at 0.5ms1. Rinsing at 20 C using (a) water, and (b) Advantis 210;and rinsing at 70 C using (c) water, and (d) Advantis 210.

Fig. 8 Area proles for rinsing type A deposit with water at 0.26, 0.4, and 0.5ms1 for temperatures of (a) 20 C, (b) 30 C, (c)50 C and (d) 70 C. Data shown are average of three repeats, with standard deviation shown as error bar.


Fig. 9 Theby eye usin50, and 70

data pointted as averdeviation a

Chemicadecreased tthe ow wano signica0.5ms1. Texists whewhich littletemperaturow velocit50 and 70 Cincreasingshortest cletimes wereing that radecrease cltemperaturincreasingtemperaturpreferred aronmentaluid at 70

may be acc

4. Co

Rheologicayeast slurrThe deposibe more intime of thethe deposittic when hbe removecleaning being depositproved effeof volume rswelling an

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ry currently use. i.e. that there is a cope for cleanings thompdicatcanre. TC, if70 Cies. Tof clre isa lowlantbilitstiga

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cticeineerra, J.,hancleaning times for type A deposit determinedg 2wt% Advantis 210 at temperatures of 20, 30,

C and ow velocities of 0.26, 0.4, and 0.5ms1.

there were at least two repeats. Results are plot-ages of these repeats and error bars of standarddded.l cleaning using 2wt% Advantis 210 at 20 and 30 Che cleaning time. The cleaning time decreased ass increased from 0.26 to 0.4ms1 but then showednt change as the ow was increased further tohis would suggest that for this deposit a velocityre chemical action is most effective, and beyondincrease in removal is not seen. Increasing the

e from20 to 30 Cdecreased the cleaning time at allies. Chemical cleaning using 2wt% Advantis 210 atgave a further decrease in the cleaning time with

ow velocity. Chemical rinsing at 70 C revealed theaning times for all ow velocities. Similar cleaningobserved when rinsing at 30 and 50 C suggest-

ising the temperature from 30 to 50 C would noteaning time, and that suggests there is a range ofes where chemical action may not be enhanced bythe temperature. In industrial practice, if a lowere can give similar cleaning efciency this would bes it would lead to a cost reduction and lower envi-impact. Industrial practice is often to use cleaningC, but this work suggests that lower temperatureseptable if time is not critical.

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l characterisation of yeast foam has revealed thaty can be used to mimic industrial yeast deposit.t viscosity and yield stress might be increased todustrially representative by increasing the agingdeposit. Studying the viscoelastic properties of

s also revealed that the deposit became more elas-eated to 70 C. This deposit also takes longer tod by the ow. The use of rheology in predictinghaviour should be further investigated. Measur-reduction by estimating the area from images hasctive for these experiments, however an indicationemoval would be more useful in capturing depositd erosion phenomena.l rinsing using 2wt% Advantis revealed a visuallyce at all temperatures and ow velocities investi-nding suggests that a visually clean surface canat lower temperatures and ow velocities than

pathogendrug resi

Christian, GdepositsUniversi

Christian, Gphysics aDairy Te

Cluett, J.D.,nishesEngineer

Cole, P.A., RoCompariscale pip

EHEDG Year20 (Supp

Friis, A., Jenprocessi80, 2812

Fryer, P.J., AsclassicaScience &at would have a lower environmental impact andarable cleaning times for rinsing at 30 and 50 Ced there is a range of temperatureswhere chemicalnot be further enhanced by increasing the tem-his suggests cleaning at lower temperatures, i.e.a CIP regime is not time limited. Chemical clean-showed the shortest cleaning times for all ow

o reduce the cleaning requirement of thedetergenteaning the data suggests the most efcient tem-50 C. The detergent phase could then be carrieder temperature and/or concentration to remove

s. The next stage of the work will be to test they of these ndings in an industrial fermenter andte the effect of decreasing the chemical concentra-

dgements

s wish to thank the EPSRC and Heineken UK Ltdon of an EngD studentship to KRG. This paperlts fromtheZEALproject TP//ZEE/6/1/21191,whichlfa Laval, Cadbury Ltd., Ecolab Ltd., NewcastleScottish & Newcastle Ltd., GEA Process Engi-., Unilever UK Central Resources Ltd., Imperial

Science Technology and Medicine, GlaxoSmithK-r Optics Ltd. and the University of Birmingham.ct is co-funded by the Technology Strategylaborative Research and Development programme,open competition. For more information visit.innovateuk.org.

s

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Othman, A.M., Asteriadou, K., Robbins, P.T., Fryer, P.J., 2010.Cleaning of sweet condensed milk deposits on a stainlesssteel surface. In: Wilson, D.I., Chew, Y.M.J. (Eds.), Proceedingsof the Fouling & Cleaning in Food Processing. 2010 Conferencein Cambridge, Session V. Department of ChemicalEngineering, Cambridge, pp. 174182.

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Tamime, A.V., 2008. Cleaning-in-place: Dairy, Food and BeverageOperations, Society of Dairy Technology Series.Wiley-Blackwell, London.

Characterising the cleaning mechanisms of yeast and the implications for Cleaning In Place (CIP)IntroductionCleaning yeast in brewery operationsApproach adopted

Methods and materialsForming the deposits for cleaningEquipmentCleaning rig procedureRheological characterisationMiniature fermentation system

Results and discussionRheological characterisationDeposit removal profilesThe effect of mechanical flow and temperatureThe effect of chemical

ConclusionsAcknowledgementsReferences

goode 2010 food and bioproducts processing

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