Basic Principles of Whey Powder Processing

Handout Document at the Whey Seminar in Poland, February 2002

By Mr. Claus Siegaard, Niro A/S

Drawing by Mr. Tony Svatik, Niro Australia Pty. Ltd.

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Introduction:

This paper is meant to give you a short introduction to the processing of whey and

some of the technology behind. More detailed information will be discussed during

an actual project enabling both parties to optimize the process for the given pa-

rameters.

Today the attitude towards whey has changed and whey is considered as a valu-

able product that can be processed into many different powder products. There-

fore, the time has come to evaluate the way in which the whey business is carried

out today. Moving yourself from a business where the whey is used primarily as

animal food or simply dumped into small lakes around the country into an ad-

vanced utilization of the whey and its components goes hand in hand with the de-

velopment of the agricultural sector in the country to meet European Union rules

and regulations.

Instead of paying the local government a penalty for the discharge of the whey or

having cost in connection with transporting the whey to the farmer you can now

sell the products to large dairies specialized in utilizing the whey.

In principle, everybody can build a whey powder factory, but it is important to re-

alize that a certain volume of whey is required to have a profitable production. We

estimate that depending on the products you intend to produce you should have a

minimum of 300,000 l/day of whey. As many cheese dairies do not have such vol-

umes we often see either several dairies considering a co-operation established

on one common whey powder factory, or one dairy invests in the facility and buys

the whey from the neighbouring dairies on multiple years' contract.

When discussing whey, you must distinguish between sweet and acid whey. You

even have to distinguish between different types of whey within these two groups.

Further, having a good whey powder still requires that your whey quality is good -

processing whey into powder does not make miracles. For this reason the design

of a large whey powder factory often also requires changes/modifications in the

process of the cheese dairy.

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The Cheese Dairy:

As mentioned, changes often have to be foreseen at the cheese factories. Typically,

the changes required will be a fines-saver, fat centrifuge, silos, additional cooling

system, heat treatment and occasionally a nano-filtration plant for pre-concentrating.

The fines-saver is a requirement to improve the processes downstream. Typically this

should be designed as a continuos inline process so that no temporary storage of the

warm whey is required. The cheese fines will simply block the centrifuge and the nano-

filtration plant, reducing the capacity on these units and thus the overall process.

The centrifuge is introduced to lower the fat content in the whey down to 0,05%

again allowing for optimal running conditions of the processes down stream, but

also to increase the quality of the final whey powder products. Also the centrifuge

should be designed as an inline continues process. The whey fat can be used for

standardization of the milk to the cheese production

It is important to have minimal storage time of the whey prior to above processes,

as storage at high temperature will increase the microbiological level of the whey.

The cheese fines and lactose in the whey make good growth material for bacteria

and a temperature of 30-40°C only increases the growth. It is not advisable seen

from an energy consumption point of view to cool the whey at this stage, as the

whey should be temperated, when being processed through the fat centrifuge.

When the whey has been cleaned for fines and the fat removed, it should have a

heat treatment and be cooled to approximately 6°C and could now either be

stored for transport to the whey powder factory or alternatively processed through

a nano-filtration plant. Different manufacturers have different philosophy regarding

the required heat treatment of whey, so a thermisation or a low pasteurization

would most likely be the applied heat treatment, but of course it depends on the

type of cheese manufactured and the general bacteriological level of the factory.

The nano-filtration plant (NF) can work as an inline or batch plant and can have

larger capacity than what is required for the inline process equipment. A reason

for introducing the NF plant is to lower the cost of transportation between the

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cheese dairy and the whey powder factory and at the same time the salt content is

decreased. The NF plant will typically increase the total solid to 20-22% TS from

the 6.25 %TS in the liquid whey, and thus reduce the overall volume to approxi-

mately 1/4 that should be transported. Other reasons being the functionality of the

downstream processes and the characteristics of the whey powder.

The NF plant is designed to achieve a highly specific separation of low molecular

weight compounds being water and monovalent ions like NaCl. The membranes

are usually of the thin film composite type where it is possible to tailor the struc-

ture of the surface layer to achieve their special characteristics. The NF plant

performs a unique role by simultaneous separation and concentration function. A

partial demineralization up to 40% can be achieved using the NF technology.

The storage temperature of the whey should be as low as possible, but preferably 6°C -

this to ensure less changes during storage and transport. When the whey is being

transported - concentrated or non-concentrated - it is important that the temperature

does not exceed 10°C, again to avoid any unwanted microbiological growth.

The Whey Powder Factory:

After the whey is received at the whey powder factory it should be stored in insu-

lated silo tanks to ensure that the temperature does not increase further. The dif-

ferent types of whey are influenced differently by an increased temperature and in

acid whey the acidity will prevent the growth of bacteria to some degree, and the

temperature importance is therefore of less concern.

Drawing by Mr. Eric Francen, Niro A/S

5

As different whey types have different characteristics, and therefore requires dif-

ferent process lines, it is important to know the basis whey prior to designing the

whey powder factory. Perhaps the factory will receive both sweet and acid whey

and many variants within the two general types, some of which can be mixed and

processed into a homogeneous powder. However, some types of whey you do not

want to mix due to the functionality of the process and others because of the

functionality and the applications to which you can sell the powder. In general, we

can say that you do not want to mix sweet and acid whey. The level of minerals

combined with the pH, especially Ca++, in acid whey is so that you must reduce

the level to obtain a smooth operation of the evaporator. If not reduced, the acid-

ity, Ca++ level and the temperature in the evaporator will generate calcium phos-

phate precipitation and reduce the running time of the evaporator considerably.

The powder product to be produced is very dependent on the upstream proc-

esses, and in most cases outlines the design possibilities, as can be seen from

the block diagram below (limited version).

Several different powder products can be manufactured from acid whey, but in

each case it requires a specialized upstream process. The first product mentioned

in the block diagram is CAWY high Ca++ (Crystallised Acid Whey Powder) and the

Ca++ Ca++UF

Evaporation

NeutralizationMg(OH)2

Crystallization

Spray Drying

CAWY low Ca++

Evaporation

NeutralizationCa(OH)2

Crystallization

Spray Drying

CAWY high Ca++

NF

Evaporation

Crystallization

Separation"Decanter"

Drying

Lactose Powder

DCP

Acid Whey

Fines Screening

Fat Centrifuge

Heat Treatment

UF

Evaporation

Spray Drying

WPC 80

NeutralizationMg(OH)2

NF NFPermeate

Permeate Permeate

DCP

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upstream process includes an evaporator, neutralization and crystallization. The

evaporation process is included, as it is cheaper to remove water from the whey in

an evaporator than in a spray dryer, and because you will get a better / heavier

powder when manufactured at higher TS. The evaporator could be designed with

an MVR (Mechanical Vapour Recompression) pre-evaporation section followed by

a TVR (Thermal Vapour Recompression) finisher section and finally a flash cooler

lowering the temperature of the concentrated whey when leaving the evaporator

from 45°C to 30°C allowing an initiation of the crystallisation and hence a smaller,

evenly distributed crystal size.

The design of the finisher is

critical as a wrong solid

content in combination with

a too high temperature can

give protein denaturation

and calcium phosphate

precipitation and even

browning reactions and a

too low temperature can

give lactose crystallisation

in the evaporator resulting

in blockages and poor sub-

sequent crystallization. The technology (MVR/TVR) of the evaporator can be

changed depending on what type of energy sources that is best priced in the area

in question.

The water removed in the evaporation process is called condensate and in the

case of acid whey some of the acidity will be distilled over in the condensate.

Therefore, the condensate must be polished before being used as e.g. general

cleaning water or flush water within the factory.

The concentrate having a total solid content between 55-60% TS should be neu-

tralized to eliminate the bad influence by any left acidity in connection with drying,

Drawing by Mr Eric Franzen, Niro A/S

7

being for example a sticky behaviour. Prior to spray drying, the concentrated whey

should be crystallized.

The process of crystallization is very essential to the final result of the powder.

First, the initial crystallisation ensuring small crystals is done by having a flash

section on the evaporator and by seeding milled lactose crystals to the crystallisa-

tion tanks.

Secondly, choosing the right crystallisation tank is very important. Two important

features when choosing a crystallisation tank are the agitation system and the de-

sign of the product outlet. The agitation system is important because it should en-

sure a continuous and even mix throughout the tank during the period of crystalli-

sation. The design of the product outlet is important, because it can be difficult to

empty a tank with crystallised product as it tends to block.

Having chosen the right tank you should also have the right philosophy regarding

the crystallisation process. In this respect you should ensure the correct filling

time and correct cooling temperature (�t) during the crystallization period so that

you will have the optimal crystal sizes. The correct philosophy requires numerous

crystallisation tanks, typically between 5-7, depending on the capacity, but based

on a 20 h/day continuous operation. A wrong crystallization will give a poor quality

of the dried product and major problems during the drying process.

Drying of a crystallised whey product of this type will usually require a spray dryer

of the compact dryer type. The compact dryer is especially good for whey applica-

tions in general, as it is reasonably adaptable to variations in the feed quality.

Further, the compact dryer will be equipped with a rotary atomizer ensuring the

correct powder characteristics, but also lowering the spare part consumption

compared with nozzle atomization. The neutralization upstream to the crystalliza-

tion is done to facilitate the drying process. Optimizing further on the drying proc-

ess, two techniques can be applied. Fines return (FRAD) of the cyclone fraction to

the atomization zone will coat the wet concentrate particles when leaving the at-

omizer, giving less deposits on the chamber walls and ceiling. To reduce the de-

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posits on the chamber walls further, a wall sweep system will typically be in-

stalled. The wall sweep system introduces a temperated air onto the drying cham-

ber wall via an external source. The advantage of having an external wall sweep

system is avoiding the disadvantage of an internal sweep system on which pow-

der will stick as the system does not clean itself.

The internal static fluid-bed on the dryer

finalizes the concept - giving an im-

proved drying economy together with

the flexibility of accepting variations in

the feed and thus in the powder product

when entering the static fluid-bed.

Now having a dry product you must still

ensure high processing qualities, e.g.

cooling of the powder to below 30-35°C

to ensure that the powder does not

cake or self-ignite neither in the silo

system nor in the powder bag itself.

Cooling the powder can be done with different technologies based on the same

principle of using dehumidified cold air. You can choose to have a VIBRO-

FLUIDIZER® after the dryer, into which conditioned air is introduced, ensuring the

powder temperature to be correct when leaving the VIBRO-FLUIDIZER®. You can

also choose to let the powder cooling take place in for example a pneumatic

transport system - again using conditioned air for the transport. When conditioning

the air, it is important to design a system that takes into consideration the relative

humidity % (RH%) that is optimal/maximal for not altering the chemical composi-

tion of the powder, but only the temperature.

Some powder manufacturers produce crystallized acid whey products with less

Ca++ (CAWY less Ca++ indicated in our block diagram), a partial demineralisation.

To manufacture this product requires a new technology called the de-calcium

phosphitation process or the DCP process.

Drawing by Mr Eric Franzen, Niro A/S

9

As can be seen from the block diagram, the whey is first filtered through an ultra-

filtration plant (UF plant). Due to the pore size of the membranes, the major part

of the minerals passes through the membrane into the permeate. The retentate

that includes the protein will be processed into powder together with the permeate

that will be mixed back after processing through other processes first. The perme-

ate is processed through an NF plant that increases the TS% up to 20% allowing

an optimal utilization of the DCP process. In the NF plant you will have up to 40%

demineralisation. From the NF plant the retentate is processed through the DCP

process. In the DCP process the pH and temperature will be adjusted for optimal

precipitation of the calcium phosphate. Depending on the required purity of the

calcium phosphate, the product can be processed through numerous separation

and washing processes. Finally, you will end up with a slurry of calcium phosphate

and a stream of supernatant and wash water. The supernatant and wash water

will be mixed and returned to the retentate from the UF plant. The supernatant

and wash water are rich on lactose and will increase the yield of the drying proc-

ess. The calcium phosphate slurry can be dried to obtain a calcium phosphate

powder.

ff

Powder

Cyclone

Steam

ClarifiedPermeate

Permeate Silo

NaOH

Drier

Wash Water

Decanter

Nozze lClarifierMSE300

HoldingTank

Drawing by Westfalia Separator AG

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The DCP process prolongs considerably the running time of the downstream pro-

cess - especially the evaporator running time will increase. In some designs, it

would even be possible to reduce the capacity of the evaporator.

The DCP process is a huge advantage for the downstream processes, because

not only will it reduce the calcium phosphate deposits in the evaporator, but the

advantages of not having these deposits are less energy consumption in the

evaporator, less pronounced fouling and better subsequent crystallization.

The mix between the UF retentate and the DCP supernatant and wash water is

then processed through a similar process as for the CAWY high Ca++ - similar

considerations regarding technology and process (evaporation, neutralization,

crystallization and drying) apply to the design. Further, this process requires less

cleaning and thus less consumption of chemicals.

Moving to more advanced products such as WPC and lactose again introduces

new technologies and points where you should focus on obtaining the absolutely

optimal product.

When discussing WPC products you

should differentiate between low or high

protein WPCs. A WPC 35 (35% Protein

in TS) can be produced on a compact

dryer in a good quality, but when it

comes to a WPC 80 (80% protein in

TS), the Tall-Form dryer technology

should be introduced. The Tall-Form

dryer has nozzle atomization that gives

the requested powder properties to the

powder and is designed with a special

exhaust system called a bustle. The

bustle ensures a lower pressure drop in

the exhaust zone, which reduces the

powder loss to the exhaust system and

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finally to the atmosphere. The Tall-Form dryer is further equipped with a VIBRO-

FLUIDIZER® for 2-stage drying. This results in a low particle temperature during

drying and a powder with good solubility is achieved.

The reason for this request is that WPC 80 is a very light powder, as it will typi-

cally be processed with a TS% in the feed of 30-35%.

When producing WPC 80 you will have a large stream of permeate from the UF

plant. This permeate will include most of the lactose. To improve the quality of the

lactose when processed into powder, the NF and DCP technology is introduced

again. After these processes, which in principle can be compared with the proc-

esses for the CAWY low Ca++, the supernatant and wash water will be mixed and

processed through an evaporator. The evaporator will in this case not be designed

with a flash cooler, as when producing lactose powder you want to have larger

crystals due to the yield %, and easier downstream process, for example easier to

remove water in the decantation process. If the lactose crystals are too large, you

will mill down to the required size after drying. The crystallisation will therefore

start at 45°C with seeding of lactose powder.

The decantation process is a separation process, where you wash your crystallized

lactose. The wash water together with the mother liquor contains some lactose and

all the minerals and impurities, and should be discharged / sold as animal feed.

Having the DCP process as an integrated part of the lactose process reduces the

volume of wash water required and thus limits the volume that should be discharged,

giving a more profitable operation. Further, the reduction of calcium and other salts

minimizes the impurity of the lactose crystals as the seeding generated by the pre-

cipitation of the salts and the lactose crystals growing on these salts will be reduced.

Lactose powder is marketed as 3 different grades:

� Technical lactose.

� Edible lactose.

� Pharmaceutical lactose.

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The required purity is obtained during the washing process. Pharmaceutical lactose is

produced by dissolving lactose crystals, re-crystallization and further washing.

Drying of lactose requires a special lactose dryer that can adapt the irregularities

in the feed flow that will occur after a decantation process based on differences

between the crystallized feed that will occur when changing crystallization tank.

The lactose dryer should have a cooling section

ensuring that the lactose powder is cooled to 30°C

or below before being transported to the silo sta-

tion. Because the design of the evaporator and

crystallization process is done to ensure large

crystals giving better yield and an easier process,

you will have a lactose powder with rather large

crystals. Many manufacturers therefore mill down

the lactose crystals to the required size. The mill-

ing process is a complicated process and explo-

sion is a risk that should be taken seriously.

Therefore, you will typically find the milling process

in a separate room. You can get quality milling

equipment designed to withstand explosions gen-

erating a pressure of 3 bar g or 10 bar g - it is

advisable to invest in the 10 bar g system.

Why Utilize the Whey?

Can you afford NOT to? If you do not utilize the whey, then you might pollute the

local environment ruining the small rivers and the life in them.

Above description has outlined a few possible products that can be manufactured

from acid whey.

Manufacturing these products will not only lower the total BOD discharged into the

environment, but it will also give you only one source of whey waste water being at

the whey powder factory - a stream that you can control and decide to treat. Not

Drawing by Mr Eric Franzen, Niro A/S

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having the whey powder factory will give you 10-15 cheese factories, each with its

own uncontrolled stream of whey and you have to face the consequences of that.

Manufacturing these products is a profitable process, if you have a daily volume of

minimum 300,000 l.

Who to Choose as Engineering and Know-how Partner?

GEA has a huge experience in processing whey into numerous products and we

have most of the technologies required in-house. Where we find it convenient, we

work together with sub-contractors, who are leading within their fields of expertise

allowing us to present the best technological solution, looking not only at the

processing economy but also at the whey powder product quality.

One advantage for you, when doing business with GEA, is that you need only one

contractor for your total process. This makes you communication and project de-

velopment work easier as you will have one point of communication ensuring that

the total project will become a success. You will not have any risk in miscommuni-

cation/misunderstanding between you and different suppliers - GEA is responsible

for the communication within its project organization being inhouse companies or

subcontractors - you will communicate with the project manager group, only.

Having experience from all around the world, GEA knows the requirements of for

example local building companies, local electrical companies and local installation

companies that you may choose to contract with - we have a well-documented

and easy understandable design/engineering documentation that will help your

own direct sub-contractors understand how to co-operate with us.

For further information, please call your local GEA Office.

GEA Process Technology Warsaw sp.z.oo, Niro DivisionJerozolimskie Business ParkAl. Jerozolimskie 146a,02-305 Warszawa, 3rd floorTelephone: +48-22-608-1400 Telefax: +48-22-608-1425

+48-22-608-1410 +48-22-608-1426E-mail: geaptwaw@it.com.pl.