01.30.55.110-yeast propagation and management 2008 (1).pdf

7/21/2019 01.30.55.110-Yeast Propagation and Management 2008 (1).pdf

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Rules, Standards & Procedures

Brewing Process Equipment Standard

YEAST PROPAGATION &YEAST MANAGEMENT

1.INTRODUCTION 2

2.QUICK FLOW 2

3.YEAST MANAGEMENT 3

3.1BASIC DESIGN YEAST STORAGE PLANT 33.2YEAST STORAGE CELLAR DISTRIBUTION 33.3YEAST PITCHING 4

3.3.1 Consistency & dead cell Measurement 43.3.2 Pitching rate Measurement 53.3.3 Yeast Dosing line 5

3.4YEAST HARVEST &PURGE 73.4.1 Yeast Harvest line distribution 73.4.2 Number of harvest lines 83.4.3 Number of harvest to 1 YST 83.4.4 Yeast cooling 83.4.5 Yeast harvest control 9

3.5YEAST STORAGE 113.5.1 Number of yeast plants in case of multiple yest strains 113.5.2 YST Size 113.5.3 Number of YST 123.5.4 Yeast homogenisation method 123.5.5 Gas block or foam catcher 133.5.6 With or without carbon filter in air supply 133.5.7 Gas supply lines 143.5.8 YST cooling 16

3.6WASTE YEAST PLANT 163.6.1 Yeast In activation 163.6.2 Control of discharge 16

4.YEAST PROPAGATION 17

4.1BASIC DESIGN YEAST PROPAGATION PLANT 174.2DRIED YEAST OR CULTURE YEAST 184.3INTAKE OF COLD-OR HOT WORT 184.4REHYDRATION OF YEAST 204.5PROPAGATION 21

4.5.1 Propagator size 214.5.2 Mixing in the propagator 214.5.3 Aeration of the propagator 224.5.4 Non aerated steps in F(S)T or One brew fermentor 234.5.5 Propagator cooling 23

Yeast Propagation & Yeast Management

HMESC: 01.30.55.110 Date: April 2008 Issue: 05 Page: 1of 23


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1. INTRODUCTION

2. QUICK FLOW

--- Not recommended --- --- Add ons ---

With proximity switches

Automatic execution with mix proof

valves

Microscopic cell count Laboratory Thoma cell counter & dead

cell measurement

Aber yeast monitor

Mass flow measurement in dosing line

Weighing cells YST

More than one dosing line More than one dosing line

Separate CIP of dosing line

With proximity switches

Automatic execution with mix proof

valves

2nd harvest/purge line directly to the

WYT

1 harvest to 2 YST 1 harvest to 2 YST

Deep cooling in the YSTTurbidity measurement for detection

yeast/beer

Density measurement for detectionyeast/beer

Small purge based on volume only

Every yeast strain its own yeast plant

>3 YST

Stirrer

Iso-mix (pm)

Foam catcher

With carbon filter in air supply

With steaming facilities in aeration

Deep cooling in the YST

> 1 WYT

Inactivation by heat

Chemical inactivation

Automatic discharge of the WYT

Pure Culture Yeast

Sterile wort intake Hot wort intake

Rehydration using a rehydrator

Initial propagation of pure culture yeast

using a Carlsberg Flask

Mixing using a stirrer or pumping

system

Swing bend execution dosing line

One dosing line

1 harvest to 1 YST

Volumetric flow measurement & Visual detection

east/beer

Volumetric flow measurement in dosing line

Swing bend execution dosing line

1 harvest line

Inline cooling in harvest line

Yeast rehydration

Rehydration using a Carlsberg Flask

Cold wort intake

Yeast propagation

Aerated steps in propagator

Dried yeast

1 WYT

Yeast Storage

Cooling to maintain storage temperature

Homogenisation using a circulation pump

3 YST

Gas block

One yeast plant in case of muliple yeast strains

Without steaming faciilities in aeration

Without carbon filter in air supply

Mixing by aeration

Yeast Propagation & Yeast

Management

--- Basic execution ---

Laboratory consistency & dead cell measurement

No yeast inactivation

Yeast pitching

Yeast harvest

Waste Yeast Handling

CIP dosing line together with wortline

Local controlled manual discharge of the WYT




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3. YEAST MANAGEMENT

3.1 BASIC DESIGN YEAST STORAGE PLANT

Picture 3.1.1 Basic design yeast plant (functionality only)

To FS or FSTs

YEAST STORAGE TANKS

CIP

CIP Return

Head space50%

Brewhouse

YEASTCOOLER

Waste Yeast Tank

To lorryFEFE

FEFE

FSTFST

Pressure Regulation

Sterile air

Coolant

Free

Air

Inlet on max

liquid level

CIP dosingline together

with wortline

Yeast harvest:

Swing bend/flow plate execution of the cellar distribution (not indicated in picture above)

Positive displacement pump as driving force for the yeast transfer from FST to yeast storage

Flow measurement for pre- and post run activities Sight glass to detect beer/yeast transition

Yeast deep cooler to cool the yeast from FST harvest temperature until < 2 C

1 harvest line to the yeast storage and waste yeast

Centrifugal pump to empty Yeast storage tanks to the waste yeast tank

Yeast storage and pitching:

Three yeast storage tanks

Tank cooling to maintain storage temperature

Yeast homogenisation using a positive displacement pump and a recycle line

Prevent foamingo 50 % headspace

o Pre-pressurise YST before harvest (pressure as low as possible) 1 yeast dosing line (pitching)

Yeast dosing based on a mass flow measurement and laboratory consistency and dead cellmeasurement

CIP dosing line together with the wort line

Waste Yeast plant

One Waste Yeast Tank

No yeast inactivation

Local controlled manual discharge of the WYT

3.2 YEAST STORAGE CELLAR DISTRIBUTION

For investment costs reasons, the basic design for a yeast cellar is the flow plate (swing bend) execution.For quality reasons or in case of high operational costs (labour), a fully automated cellar (mix proof valves)can be considered.




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Some breweries are using proximity switches in combination with a flow plate execution.This set up is not recommended due to the following reasons:

High investment costs (equipment, automation)

Reliability (regularly break down) Equal procedures as for flow plate execution without proximity switches (to meet SHE

requirements)

The choice between the different distribution methods will be described in detail in the BDM Tank room.

3.3 YEAST PITCHING

Yeast dosing is part of the wort transfer from whirlpool to the fermenting tank. All the yeast necessary for afull fermenting tank is dosed in the first brew.

3.3.1 CONSISTENCY &DEAD CELL MEASUREMENT

Pitching rate should be based on yeast consistency measurement or if available a cell count using aThoma/Coulter counter, all corrected for the dead cells percentage. A cell count using a microscope is notrecommended since it is not accurate enough.This can be done using batch wise sampling and laboratory measurement, or inline measurement using a(Aber) yeast monitor during dosing. Yeast consistency can also be measured using the densitymeasurement of a mass flow meter.

The basic solution is based on batch sampling and laboratory measurement. Depending on the local labourcosts or requested quality, the yeast monitor can be considered.

Table 3.3.1.1: Overview consistency & dead cell measurement choice

Basic Design Add on Add On Add OnItem

LaboratoryconsistencyMeasurement

Laboratorymeasurement using aThoma Cell counter

Inline(Aber)yeastMonitor

Consistency measurement bydensity using densitymeasurement of mass flowmeter

Technical ++ + -- +

Technological

+ + ++ +

Operational - - + +

Legend: ++ = excellent+ = good0 = average- = mediocre-- = poor

Technical:

Low investment costs for the basic solution

A Thoma cell counter is more expensive than laboratory consistency mesurement

A yeast monitor measurement is expensive compared to relatively simple laboratory equipmentand batch sampling. A yeast monitor measures consistency and yeast viability

An additional density measurement to the mass flow meter (to measure consistency) is slightlymore expensive. It does not measure yeast viability

Technological:

Inline consistency measurement is independent of homogeneity.

Inline measurement measures each dosing, batch sampling only once and therefore storage timedependent.

Additional density measurement of the mass flow meter still requires laboratory dead cellmeasurement. In case of good yeast management, dead cell level is not very fluctuating. Iffluctuation is low, not every batch needs to be measured.




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Operational:

In case of inline measurement only occasional calibration measurements instead of measuring

each batch in case of laboratory measurements (labour costs) In case of good yeast management, dead cell level is not very fluctuating. If fluctuation is low, not

every batch needs to be measured.

3.3.2 PITCHING RATE MEASUREMENT

The pitching rate can be measured using inline mass flow measurement or by the decrease of weight of thecontent of the yeast storage tank. (YST)

The basic solution is based on inline volumetric flow measurement.

Table 3.3.2.1: Overview pitching rate measurement

Basic Design Add on Add OnItem

Volumetric flowMeasurement

Inline Mass flowMeasurement

Weight decreaseYST

Technical ++ + -

Technological

- + -

Operational + + -

`Legend: ++ = excellent

+ = good0 = average- = mediocre-- = poor

Technical:

Low investment costs for the basic solutiono Mass flow measurement is more expensiveo Only one inline measurement compared to weighing cells on each YST.

Technological:

Weighing cell accuracy less than mass or volumetric flow measurement

No correction for yeast concentration in case of concentration gradients for volumetric flowmeasurement

Operational:

More equipment to maintain in case of weighing cells

3.3.3 YEAST DOSING LINE

3.3.3.1 NUMBER OF YEAST DOSING LINES:

The number of dosing lines is depending on the occupation of the dosing line.The basic design is based on only 1 dosing line. In practice it is proven that single yeast breweries up to ayearly capacity of 11.000.000 hl/year can run with only one dosing line.

Even for a brewery with multiple yeast strains it is not recommended to use more than one dosing line. With aproper CIP philosophy (in compliance with the BDM CIP, cleaning before each dosing) only one dosing line issufficient.Only in case more than 16 tanks per day need to be pitches a second dosing line can be considered.

Calculation:Pitching time : 45 minutesTotal CIP time : 45 minutes




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Brewing Process Equipment StandardNumber of dosings possible per 24 h: 16 dosing actions/day




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3.3.3.2 CIPYEAST DOSING LINE

The yeast dosing line can be cleaned together with the wortline or separately.The basic design is cleaning together with the wortline.

Table 3.3.3.2.1: Choice cleaning the dosing line together with the wortline or separately.

Basic Design Add OnItem

CIP together withwortline

Separate CIP of dosingline

Technical + -

Operational

0 ++


Technical:

Low investment costs for the basic solutiono No additional valves, piping and CIP program in case of cleaning together with the

wortline.

Operational:

Operational consequence of the basic solution is:o CIP only possible in case of FST switch

Flexibility problems can occurs in case of:o More than 1 brewhouse (2 or more dosing at the same timeo Multiple yeast strains (CIP required)o In case of a lot of small fermenting tanks (many dosing/day)

3.4 YEAST HARVEST &PURGE

The yeast is harvested from the fermentation storage tank to the yeast storage tank or waste yeast tank.In case the yeast quality is good in terms of generation, visual and microbiological condition, beer type andbehavior during previous fermentation, the harvest will take place to the yeast storage tank. In case theyeast quality is insufficient in respect to the above-mentioned aspects, the harvest has to go to the wasteyeast tank.

To avoid foaming in the yeast storage tank several actions has to be taken.

First the temperature of the yeast must be lowered as soon as possible. The best way to do that is tocool the yeast using an inline cooler.

Secondly depending on the local circumstances it is sometimes necessary to harvest under a counterpressure. This counter pressure has to be as low as possible (max. 0.8bar) After the harvest thiscounter pressure has to be relieved slowly with care, but as fast as possible.

The last foam preventing action is to apply a headspace of 50 %.

During fermentation, maturation and before emptying, the Fermenting Storage tank is purged (severaltimes) to the waste yeast tank. For quality reasons it is also possible to transfer yeast from the yeaststorage tank to the waste yeast tank.

3.4.1 YEAST HARVEST LINE DISTRIBUTION

Basic design is a flow plate (swing bend) execution of the yeast distribution from fermenting cellar until theyeast storage tank.

The stipulations concerning fully automatic (mix proof valves) execution and the use of proximity switchesare the same as mentioned in Chapter 3.2




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3.4.2 NUMBER OF HARVEST LINES

The number of harvest lines depends on the number of FSTs. The basic design consists of 1 harvest lineto the YST and WYT. Depending on the number of FST, an additional line to the Waste Yeast Tank (WYT)

can be considered for harvesting or purging directly to the WYT

Table 3.4.2.1. Choice number of harvest/purge lines


1 harvest line to YST & WYT Additional harvest/purge line toWYT

Technical + -

Operational

< 36 tanks >36 tanks

Numb Legend: ++ = excellent+ = good0 = average- = mediocre

-- = poor

Technical:

Low investment costs for the basic solutiono Additional harvest and purge line without connection with the YST in case of an additional

line.

Operational:o Change over number of tanks depending on the process time.o 36 tanks is based on 18 days production time in FST. (Max. 3 harvest & 3 purge & 4 CIP/day)

3.4.3 NUMBER OF HARVEST TO 1YSTThe basic design is based on 1 harvest to 1 FST. Mixing of yeast from several FST is not allowed.

In case the YST is too small to harvest all to one YST, it can be considered to fill 2 YSTs with 1 harvest.To avoid (flocculence) differences between the 2 tanks, it is recommended to fill the YSTs alternating.

3.4.4 YEAST COOLING

Yeast can be cooled in the YST or inline. It should be realised that cooling from harvest temperature to < 2C in the tank is only applicable in case the YST is intensively mixed using for example a stirrer. If a inlinecooler is installed, cooling of the yeast storage tank is still required to maintain storage temperature.

For technical and technological reasons, the basic design is an inline cooler.

Table 3.4.4.1. Choice yeast cooling

BasicDesign

Add OnItem

Inline cooler Deep cooling in theYST

Technical + --

Technological

++ -

Operational + -

Legend: ++ = excellent





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Brewing Process Equipment StandardTechnical:

Low investment costs for the basic solutiono Deep cooling in the YST requires a stirrer in each YST

Technological: Direct inline inactivation of yeast metabolism including CO2 production (temp:


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Brewing Process Equipment Standard In case of big breweries with a additional purge line and a lot of activities at the same time, visual

control is not reliable

Risk of beer losses




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3.5 YEAST STORAGE

During yeast storage the yeast must be kept at the desired temperature to keep it in good shape for pitching.Due to heat input by the circulation pump, tank cooling to maintain the storage temperature is required. During

storage the yeast must be kept homogeneous. A slight air overpressure (max.0.05bar) is applied to preventmicrobiological contamination. If yeast quality is insufficient or if there is not enough yeast left to pitch a newfermenting tank, the yeast must be transferred to the waste yeast tank.

3.5.1 NUMBER OF YEAST PLANTS IN CASE OF MULTIPLE YEST STRAINS

The basic design will be 1 yeast plant independent from the number of yeast strains in use.

In some breweries however there are separated yeast plants installed for each yeast strain.

Table:3.5.1.1


One Yeast

plant

Each yeast strain its own yeast

plantTechnical ++ --

Technological

+ +

Operational + -


Technical:

Low investment costs for the basic solutiono Separate harvest lines incl. coolerso Separate YSTo Separate dosing lines

Technological:

With an appropriate CIP philosophy it is superfluous to separate the yeast plants in case of multipleyeast strains.

It also makes no sense, because FST are common used for all strains.

More YST required, this is a risk for longer storage times

Operational:

Higher maintenance and operational costs (additional equipment).o A lot of additional procedures are required.o More attention required of operators

3.5.2 YSTSIZE

The size of the YST mainly depends on the number of pitches per day and the FST size.

The main goal is to harvest only the amount of yeast needed. If the yield of a harvest is higher, the excessshould go directly to the WYT.Depending on the capacity calculations the number of FST to be filled per day are determining the amount ofyeast needed per day. The YST should be big enough to dose for the required number of pitching per day.

In principle the harvest yield should be always enough to fulfil the above mentioned requirement.As a rule of thumb the amount of harvested yeast should be 3 % of the FST content. For a FST with a nettvolume of 4000 hl, the yeast harvest will be approximately 120 hl with 40 50 % consistency.




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Brewing Process Equipment StandardThe amount of the purges in case no additives like tannic acid or else are used, will be another 1 %. For aFST of 4000 hl this will be 40 hl.

3.5.3 NUMBER OF YST

The number of YST is depending on the number of yeast strains in use and the technological requirementto minimize the yeast storage time. In case of only one yeast strain the basic design should have max. 3YST.

The size of the YST depends on the size of the FST. (See chapter 3.5.1

Table 3.5.3.1. Number of YST

Item Number ofYST

Number of yeast strain Production ratio in caseof multiple yeast strains1

Basicdesign

3 1 1:0

Ad On 1 5 2 1:1

Add on 2 4 2 3:1Add on 3 7 3 1:1:1

Add on 4 5 3 2:1:1

3.5.4 YEAST HOMOGENISATION METHOD

There are several possibilities to homogenize the yeast during storage. The basic design is for economicaland microbiological reasons using a circulation line with a circulation pump.Alternatives are a stirrer or the mixing system of iso mix.

One should realize that deep cooling in the tank, using the tank cooling coils, is not possible in the basicdesign.Cooling capacity is closely related to the film layer thickness at the tank wall. In case of using a circulationpump, this layer is too thick to be able to deep cool the tank content within a reasonable time. The basicsolution for cooling is an inline cooler. The tank cooling is only required to keep the content on storagetemperature.

To make sure that all yeast is homogeneous or in other words to prevent a short cut in the circulation of theyeast suspension, the position of the inlet of the recycle line should be at the maximal liquid level.

Table 3.5.4.1. Choice of homogenization method


Recycling using apump

Stirrer

Technical + -Technological

+ -

Operational 0 0


Technical:

Low investment costs for the basic solution (recycling line, valves, recycle pump)o Expensive stirrer including construction on each tank

Technological:

1 Yearly Hl produced with yeast A: yearly HL produced with yeast B: yearly HL produced with yeast C




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Brewing Process Equipment Standard In combination with an inline cooler and yeast storage tank cooling to maintain the storage

temperature, basic design is homogenous and temperature stable.

A stirrer is a better mixer than a recycle pump

Stirrers are sensitive for oil leakages (SHE)

Stirrers have a better deep cooling performance Stirrers are difficult to clean

Operational:

Flexibility: With a stirrer deep cooling in the tank is possible. This is not the case in case ofusing a recycling pumps

Maintenance costs for stirrers are higher

Iso-mix system (p.m):

The isomix is system is based on a circulation using a centrifugal pump and mixing device. The maindifference compared to the basic design, is the use of a rotating mixing machine, which is positioned belowliquid level. It looks promising, because it is combining the advantages of stirring and recycling. Further

investigation on yeast viability is needed, before this application will be released.

Yeast mixing using a centrifugal pump (p,m.):

Iso mix and also some other suppliers are offering centrifugal pumps for yeast homogenization.The results of breweries using these pumps are not evaluated yet.

3.5.5 GAS BLOCK OR FOAM CATCHER

The basic design of the yeast storage plant is to blow off the CO2 to the free air without a foam catcher.

The foam catcher (FC) can be used in case the CO2 needs to be recovered. The FC prevents fouling ofthe CO2 recuperation line and plant as a result of foam in the system (over foaming YST, foam in the CO2flow).

Fore more detailed information about the choice between a gas blocks and a foam catcher see BDM Tankroom in the Foam Catcher chapter.

3.5.6 WITH OR WITHOUT CARBON FILTER IN AIR SUPPLY

Some breweries are using carbon filters in the compressed air lines to wort aeration, yeast storage,propagation plant and other tanks using air for pressure control.

A carbon filter is not part of the basic, since most of the breweries are not using the filters neither reportingproblems related with off flavors coming from the air supply.

In case there is a problem, carbon filters are considered to be best practice to remove off flavors and othercontaminants from air.

Table 3.5.6.1. With or without carbon filter in the air supply


Without carbonfilter

With carbonfilter

Technical + -

Technological

- +

Operational + 0

Legend: ++ = excellent





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Brewing Process Equipment StandardTechnical:

Lowest investment costs for the basic solutiono Carbon filter is an additional investmento Positioned before membrane filter

Technological:

A carbon filter removes potential contaminants like off flavours from the compressed air

Operational:

Integrity check and/or planned maintenance required

3.5.7 GAS SUPPLY LINES

There are several ways to execute gas supply lines. In the drawings below you find the execution variantsfor dosing of gasses in product lines during transfers and pressure control.

Solution 1 is to be used of dosing gasses in a product.

Solution 2A is to be used in case of tanks with a individual gas supply for pressure controlSolution 2B is to be used in case of a common gas supply line with several users for pressure controlSolution 3 is to be used if a mix proof valve is superfluous. ( no product contact)

PI

PT

Solution 1: Cleanable & Product safe

PI

PT

Solution 2a: Product safe (Individual)

PI R

PT

PT

Solution 2b: Product safe (Common)

PT

PI

Solution 3




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Brewing Process Equipment StandardTable: 3.5.7.1 Overview when to apply which solution

Gassupply

Productinte

grity

Productcon

tact

Common/Ind

ividual

connections

Solution

Description

Wortline Y Y I 1 aerate wort

Carboniser Y Y I 1 carbonise bright beer

YPT Y Y I 3 aerate wort & yeast

YPT Y Y I 2a pressure control wort & yeast

YST Y Y C 2b pressure control, yeast

FT Y Y C 2b pressure control, green beer

FST Y Y C 2b pressure control, wort/green beer/young beer/mature beer

ST Y Y C 2b pressure control, young beer/mature beer

UBT Y Y I 2a pressure control, mature beer

FBT Y Y C (I) 2b (2a) pressure control, bright beer

DAWT Y Y C (I) 2b (2a) pressure control, "bright beer"

PSA Y Y I 2a pressure control, bright beer

BT (BBT) Y Y I 2a pressure control, bright beer

BT (H&T) Y Y I 2a pressure control, bright beer

RBT Y Y I 2a pressure control, mature beer

PBT Y Y I 2a pressure control, bright beer

KGF N N I 3 not product related

PVPP N N I 3 not product related

3.5.7.1 WITH OR WITHOUT STEAMING FACILITIES IN AIR (OR OTHER GAS)SUPPLY

Modern breweries more and more are using sterile filters to prevent microbiological contamination from theair supply.

In case a sterile (membrane) filter is installed steaming of the air supply is not necessary since the sterilefilter guarantees sterility.

Table3.5.7.1.1. With or without steaming facilities in the air supply


Without steamingfacilities

With steamingfacilities

Technical + -Technological

+ +

Operational + -


Technical:

Lowest investment costs for the basic solution using a sterile filtero Steam supply including valves, pressure control and others is required in case no sterile

filter is used.

Technological:




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Brewing Process Equipment Standard Steaming and sterile filtration are both securing microbiological contamination. So installing one of

the two is enough.

Operational:

Integrity check and/or planned maintenance required for sterile membrane filter

Regular steaming of the air supply is needed in case no sterile filter is installed

3.5.7.2 CIPOF THE GAS SUPPLY LINES

Modern breweries more and more are using sterile filters to prevent microbiological contamination from theair or other gas supply.

Basic installation design should be done in such a way, that CIP of the gas supply lines upstream thesterile filter is not necessary.

Down stream the sterile filter precautions to prevent contamination of the filter and supply line with liquidshould be taken. (Non-return (check) valves)

In case of direct dosing of gas into liquids, the lines from non-return valves until the dosing point should beexecuted cleanable. (Manually as done i.e at the propagator or automatic i.e. the air dosing point in thecold wort)

3.5.8 YSTCOOLING

The yeast storage tank has one cooling zone with cooling agent temperature control. To prevent freezingof the product, the cool medium temperature at the outlet is controlled using a control valve. Thetemperature must be kept at 1 +/- 1.

In the basic design, with deep cooling in the harvest line and mixing by pumping using the by-pass, coolingcapacity of the YST should be enough to keep the tank on storage temperature. In case of deep cooling inthe tank, the cooling capacity and mixing method should be designed to be able the content within thedesired cooling time.

3.6 WASTE YEAST PLANT

A basic yeast plant consists of 1 WYT. The WYT is insulated and has no cooling. The CIP of the WYT isdone lost based. (no CIP return)The size of the waste yeast tank is equal to the size of the YST.A centrifugal pump is used for yeast discharge to the lorry or truck.

3.6.1 YEAST IN ACTIVATION

Surplus yeast is a valuable protein-rich product, it can be used as human food ingredient or as an animal

feed. Surplus yeast can be applied without treatment as a wet pig feed (or less common as a cattle feed)provided that hygienic measures are taken. Surplus yeast can be conserved with chemicals or by drying inorder to extend the shelf life and to meet eventual customer requirements.

The basic design is without inactivation facilities. In case the surplus yeast is killed, one can use steaminjection or dosing an additive for chemical inactivation. Heat inactivation using steam is cheaper thanchemical dosing, using a dosing unit.

3.6.2 CONTROL OF DISCHARGE

Discharge can be controlled locally or using the plant control system. For cost reasons and the fact thatmost of the time there is no possibility to control the level of the truck or lorry using the plant controlsystem, the basic design is based on local manual control.




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4. YEAST PROPAGATION

The aim of the yeast propagation process is to produce sufficient and high vitality yeast for the first productionfermentation.After the re-hydration time the wort and re-hydrated yeast are transferred to the propagator. Then the

yeast is, after adding an amount of wort, propagated during a certain time and at a certain temperature. Duringpropagation the re-hydrated yeast is aerated and after reaching the desired apparently extract wort is added forthe next propagation step.

4.1 BASIC DESIGN YEAST PROPAGATION PLANT

Picture 4.1.1 Basic design propagation plant (Functionality only)

Carlsberg flaskto sampling

point usingsterile air

To FS or FSTs

FEFEFEFE

Wort

PROPAGATOR

To freeairPressure regulation

Sterileair

3 O2 membranes

50 % Head space

Water

FEFE

CIP

Coolant

Yeast propagation:

Swing bend/flow plate execution of the cellar distribution (not indicated in picture above)

Dried yeast

Carlsberg flask for re-hydrating dried yeast.

Centrifugal pump as driving force for the fermenting yeast transfer to FT or FST

130 Dished bottom with 3 aeration points (120 of each other)

No mechanical homogenization (only mixing by aeration)

Aeration only in propagator and not in FT or FST Yeast transfer from propagator to F(S)T as fermenting wort. (No purge)

Last 2 propagation steps in F(S)T

Temperature control using cooling coils

Slightly overpressure to avoid microbiological contamination.

Pressure control using sterile air

50 % headspace

Yeast harvest from FST after final propagation step in FST




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4.2 DRIEDYEAST OR CULTURE YEAST

For cost reasons, the basic design is based on the use of dried yeast.A lot of breweries are however still using pure culture yeast.

Table 4.2.1. Choice of yeast

BasicDesign

Add OnItem

Dried yeast Pure cultureyeast

Technical ++ -

Technological

+ 0

Operational 0 0


Technical:

Low investment costs for the basic solution. (Carlsberg Flask, Propagator)o In general additional equipment is used for a pure yeast plant. ( wort sterilisation,

additional small propagator)

Technological:

Dried yeast has always the same quality (flocculence, flavour stability, operational). Pure yeastplant has a risk of mutation

Operational:

Pure yeast plant requires constant attention

Dried yeast costs

4.3 INTAKE OF COLD-OR HOT WORT

The basic design is based on the intake of cold wort.In some breweries also intake of hot wort and/or wort sterilisation are applied.We do not recommend using sterile wort, since it is increasing the investment- and operational costs and itbrings hardly any technological advantage.

Table 4.3.1. Wort intake

Basic

Design

Add On

1

Add On 2Item

Cold wort Hot wort Sterilewort

Technical ++ - --

Technologicalaspects

0 + ++

Operational + - --


Technical: Low investment costs for the basic solution




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Brewing Process Equipment Standardo More cooling capacity (deep cooling from 100 C to pitching temperature) on propagator or

sterilisator requiredo Additional YPT tank costs due to high temperature (design pressure)o Additional sterilisator in case of sterile wort




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Brewing Process Equipment StandardTechnological:

In practice initial propagation intake with cold wort, hot wort or sterile wort are all proven to bereliable in case of a proper CIP philosophy. Intake of cold wort is giving the same security formicrobiological contamination as normal production fermentation. More security is not really

required since final steps in propagation are also with wort on pitching temperature. Security level increases in case of intake of hot wort in the propagator only for the first propagation

step, since this step is the most critical (lowest yeast concentration, highest pH and lowest alcoholconcentration). The following propagation steps in the propagator and FST are done with normalwort on pitching temperature

Intake of sterile wort is only giving slightly more security, since following propagation steps are alsousing sterile wort. Since this steps are less critical and the following propagation steps in the FSTare done with normal pitching wort.

Operational:

Additional processes and required for hot wort and for sterile wort also additional equipment

Higher occupation of propagator in case of hot wort

Additional operator attention needed.

Additional operational costs in case of heating using a sterilisator

4.4 REHYDRATION OF YEAST

Before propagation, the dried yeast has to be rehydrated with a light coloured pilsener type wort. The basicdesign is based on a Carlsberg flask. A more expensive alternative is the re-hydrator, which is used for re-hydrating dried Heineken yeast.

Table 4.3.1. Choice of rehydration method


Carlsbergflask

Re-hydrator

Technical ++ -Technologicalaspects

0 ++

Operational - +


Technical:

Low investment costs for the basic solutiono Rehydrator is more expensive than a Carlsberg flask. (including a stirrer, temperature

control, electrical heater, empty detection, sterile filter)

Technological:

The rehydrator is recommended in case of Heineken production. All needed functionality for re-hydration and process control is available on the rehydrator.

Operational:

Rehydrator is not suitable for pure culture yeast

Continuous labour activity during re-hydration uing a Carlsberg flask(I.e. manual shaking). In caseof a re-hydrator only manual filling with dried yeast.

Carlsberg flask requires almost no maintenance




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4.5 PROPAGATION

To avoid foam formation it is allowed to fill the propagator with max. 0.3bar head pressure. After finishingthe wort intake, the pressure has to be relieved to max. 0.05bar.This slight overpressure prevents outside

air coming in and thus prevents microbiological contamination.During the cleaning of the propagator an overpressure can be applied to prevent vacuum.

The propagator itself is dedicated for the propagation only. In smaller breweries often a combined yeaststorage tank and propagator is used. To avoid cross contamination this is not recommended.

Mechanical mixing of the propagator is not recommended. Mixing during aeration is sufficient.

In case a Carlsberg flask is used for re-hydration or pure culture yeast, the yeast is transferred from theflask to the YPT using sterile air. Before dosing the yeast to the YPT, using the sample point of the YPT,the sampling point can be easily sterilized using alcohol and a flame.Some breweries are using steam to sterilize the sampling point. This is not recommended since it requiresadditional equipment and it is more time consuming.

4.5.1 PROPAGATOR SIZE

The size of the propagator is depending on the fermentation volume in the F(S)T. The propagator should havea headspace of 50 %.

Topping up in the F(S)T with partial brews during the last 2 propagation steps is causing operationalproblems, especially in case of basic cellar design with manual actions. Therefore basic sizing of the YPT isbased on adding complete brews to the F(S)T.

Starting points for the table below are: Minimal cooling volume in the F(S)T is at least 2 brews Addition of partial brews to the propagator and only complete brews to the F(S)T 8 brews/F(S)T

Table 4.5.1.1 Size propagator depending on FST size and only complete brews to F(S)T

FST Size(grosshl)

BrewSize(hl)

Minimalpropagator

Liquidlevel (hl)

Vol. 1st

propagationstep in F(S)TMax. 7 x (hl)

Final vol.after last

propagationstep in F(S)T

Max. 5x(hl)

PropagatorGross vol.

(hl)

1000 100 35 235 835 70

2000 200 70 470 1670 140

2500 250 90 590 2090 1802500 250 90 590 2090 180

3000 300 100 700 2500 200

4000 400 135 935 3335 270

5000 500 170 1170 4170 340

Note: The last 2 steps are not aerated

4.5.2 MIXING IN THE PROPAGATOR

Stirrers or pumping systems using a by -pass are not recommended, since mechanical agitation of thepropagator content is not allowed..Mixing will be done by the aeration flow and CO2 production during fermentation.




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4.5.3 AERATION OF THE PROPAGATOR

To stimulate yeast growth and yeast vitality, additional aeration of the propagation wort should be applied

for the first propagation step(s). Additional aeration is not allowed for the last 2 propagation steps. Thismeans :

Total 3 propagation steps additional aeration during the first propagation step

Total 4 propagation steps additional aeration during the first 2 propagation steps

For mixing reasons there are 3 injection points at the bottom of the tank. To get good mixing, aeration is doneusing 3 membranes in the bottom of the propagator. The membranes are placed 120 from each other. It isnot necessary to install a blocking detection. If one of the dosing points is locked, this is easily visiblethrough the sight glass on top of the propagator. A simple Rota measuring device is sufficient for the airflow measurement, aeration flow needs to be tuned only once based on the level of the last propagationstep.

To make sure that the air pressure in front of the membrane is always at least a 0,5 bar higher than at the

product side, a pressure transmitter in the aeration line is necessary. To avoid contamination caused bysweating of the membrane, it is advisable to maintain always a small airflow through the membrane.

The maximal air pressure on membrane is 1,5 bar.

It is recommended to use transparent hose for connection to membrane to make blockings visible.

Picture 4.5.2.1. Overview aeration propagator

Air

PCPC

Rota measuringin litres/min

Pressure 0,5 bar higher

then pressure in the tank

Controlled on/off valvewith small borehole

PCPC

0 500 50

Pressure reducer6 2 1 bar

Sterilefilter

Controlled on/off valve

Yeast propagator

Transparant hose provided

With quick clamp hose

connections

Pressure transmitter,Foam detection,Overpressure valve,Underpressure valve,are not shown on this scheme, but

are present!

Pressure

control YPT




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It is recommended to change the membranes after cleaning and disinfection. The autoclaved membraneswith housing are replaced before the next propagation using alcohol to disinfect. It is not necessary toapply steaming of the system. The system after the sterile filter can be considered as sterile.The original CPM housings will be applied to fit the membranes to the tank.

Picture 4.5.2.2.Picture membrane housing

Membrane

Substitute peace to be placedbefore propagator cleaning

Difficult to clean when membranes

remain in position, so apply

This part including membranes

to be autoclaved in the laboratory

before propagation.

Pipe solution indicated, however the same

principle is for the tank cone execution.

4.5.4 NON AERATED STEPS IN F(S)TOR ONE BREW FERMENTOR

The basic design is based on propagation of the last 2 steps in a FT or FST. In case the minimal coolinglevel of the FST is more than 2 brews a so-called One Brew Fermentor can be considered.

The size of this fermentor should be based on a nett volume of 20 % of the F(S)T.

4.5.4.1 AERATION LINES WITH OR WITHOUT CARBON FILTER

See chapter 3.5.6

4.5.4.2 AERATION LINES WITH OR WITHOUT CIPOR STEAMING FACILITIES

See chapter 3.5.7and 3.5.7.2

4.5.5 PROPAGATOR COOLING

The propagator has besides the cone cooling two cooling zones on the shell, with cooling agent supplyflow control to control the fermentation temperature.

The cooling medium is alcohol/water. The cooling zones must be corresponding with the intake volumesfor the propagation steps.

01.30.55.110-yeast propagation and management 2008 (1).pdf

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