Westfalia Separator MSD 90-01-076

Mechanical SeparationDivision

Westfalia SeparatorFood Tec GmbH

Dipl.-Ing. Arnold Uphus

Milk fat processingButter and Butteroil / AMF ( Anhydrous Milk Fat )

1

2

List of contents

1 Introduction 4

1.1 Milk fat products using a buttermaking machine 4

1.2 Milk fat products using a butteroil process 5

2 Buttermaking 6

2.1 History 6

2.2 Butter processing line 7

2.3 Cream treatment 8

2.4 Cream treatment for making sour cream butter 12

2.5 Cream pre-heating 12

2.6 Buttermaking machine 13

2.7 Dosing station 15

2.8 Control 16

2.9 Butter distribution 18

2.10 CIP system 19

2.11 Reworkers 20

2.12 Special processes for the production of milk fat products 22

2.12.1 Milk fat with reduced fat content 22

2.12.2 Butter with vegetable fat additives 23

2.12.3 Butter production with reduced content of solids non fat 24

3 Butteroil production (AMF) 26

3.1 Introduction 26

3.2 Chemical/physical correlations 26

3.2.1 Definition and designation of milk fat 27

3.2.2 Characteristics of fatty acids 31

3.2.3 Phase inversion 32

3.2.4 Minimising the emulsion phase 37

3

3.2.5 Reducing the free fatty acids 38

3.2.6 Peroxide number 38

3.2.7 Phospholipid distribution 39

3.3 Processes used for production of butteroil 41

3.3.1 Standard process using buttermilk 42

3.3.2 Process using ß-serum and secondary skim 44

3.3.3 Processes for butter processing 46

3.3.3.1 Melting the butter blocks 47

3.3.3.2 Making butteroil from sweet cream butter 47

3.3.3.3 Processing of salted sweet cream butter 49

3.3.3.4 Production of butteroil from sour cream butter 51

3.3.3.5 Processing of Cream and Butter with a high FFA content 52

3.3.3.6 Addition of antioxidants 53

4 Machines used for making butteroil 54

4.1 Cream concentrators 54

4.2 Oil concentrators / oil polishing separators 55

4.3 Skimming separators 58

4.4 Three-phase decanters 59

4.5 Butter melting system BMSA 5000 61

4.6 Vacuum unit 62

5 Bibliography 64

4

1 Introduction

In the milk fat field, Westfalia Separator nowadays offers the complete range of production methods

for various end products. The methods can be classified under two main groups:

1.1 Milk fat products using a buttermaking machine

Cream 40 %

Pasteurisation

Crystallisation

Creampre-heating

Butter churnBUD

Butterdistribution

Butter packer

ButtermilkSeparation

Buttermilk

Consumers Bulk Butter

Butter reworker Butter melting

Butter packerRecombined

ButterButteroil

production

Consumers

Figure 1: Westfalia Separator milk fat processing using the example of buttermaking

5

1.2 Milk fat products using a butteroil process

Cream 40 %

Pasteurization

Creamconcentration

Buttermilkseparation

Phaseinversion

ButtermilkOil

concentration

Oil polishing

Coolingsystem

Pin worker

Resting tube

Butter(GoldenFlow)

Vacuumtreatment

Butteroil

Consumers Crystallization

Separation/Filtration

Stearin Olein

Soft butter

Figure 2: Westfalia Separator milk fat processing using the example of butteroil production

6

2 Buttermaking

2.1 History

Westfalia Separator has been involved with manufacturing and delivering buttermaking equipment

since the 1920’s.

Production of the first timber butter vat with a capacity of 25 l cream started in 1929. Production of

butter vats was closed down only in 1950.

In 1941, a contract was signed between Westfalia Separator AG and Dr. Fritz, the inventor of the con-

tinuously operating buttermaking machine; this enabled us to use the Fritz system on an industrial

basis.

In the same year, the first prototypes of the continuously operating buttermaking machine appeared

on the market. This was followed immediately by series production of the type BUA with a capacity of

500 kg/h. Then followed the types BUB 1500 with a capacity of 750 kg/h and the type BUA with a ca-

pacity of 400 kg/h, and these were built approximately until 1960/1963.

In response to higher production levels in the field of sour cream butter, development of the type se-

ries BUC commenced at the end of the 1950’s. The BUC 800 with a capacity of 800 kg/h butter was

built between 1960 and 1972.

The BUC 1500 was also developed in 1964 for a capacity of 1,500 kg/h.

Higher capacities were reflected in 1969 with the type BUC 3000 with a capacity of 3,000 kg/h. In

1974, the sales program was extended to include the type BUC 4000 with a capacity of 4,000 kg/h.

Development of the new BUD generation was commenced at the end of the 1970’s.

7

2.2 Butter processing line

The following is a schematic representation of a butter processing line.

Cream 40 %

Cream treatment

Cream storage

CIP System Cream pre - heating Culture treatment

BDSB Dosing SystemButtermaking machine

Butter distribution

Butter packaging

Salt brine preparation

Figure 3: Flow chart of buttermaking

8

2.3 Cream treatment

The primary aim of cream treatment is crystallisation of the fat globules in order to achieve adequate

phase inversion.

fat nucleus

( Triglycerids solid or liquid )

protein

lecithin

H2O

H2O

Water

Figure 4: Cross-section through a fat globule, according to Kiermeier

The crystallisation or cream treatment process depends on the conditions or regulations which obtain

in the specific country.

In the past, central Europe mainly saw the production of sour cream butter, whereas nowadays sweet

cream is now virtually used exclusively for churning into butter.

Slightly cultured butter can be achieved by adding suitable cultures, e.g. using the NIZO method.

When butter is made from sweet cream, sweet buttermilk is obtained, and this can be used very effi-

ciently in subsequent processing.

Legal requirements, relating to texture for instance, continue to result in differentiated cream treatment

in Germany.

Sweet cream butter is generally made in other countries. In line with the national laws in a particular

country, the cream is pasteurised and then cooled to approx. 5 - 6° C.

9

Mechanism of butter formation (Kiermeier)

fatglobule

intact milkfat globule

H2O

H2O

protein

lecithin

fatfat

air

air��

��

��

air

air

��

H2O

H2O

air

foam

��

��

��

breaking of foam

butter grainfat

fat

fat

Figure 5: Foam theory of butter granule formation

10

The cooled cream is stored in isolated tanks. The crystallisation heat (latent heat) which is released

during the crystallisation process generally raises the temperature of the cream by 1 - 2° C. When the

tank has been filled, the cream should be allowed to stand for 8 - 12 hours (crystallisation time).

When the tank is being filled and when the cream is allowed to stand during the crystallisation time,

agitators should not be operated; this avoids the fat globules being damaged and also avoids hinder-

ing crystal growth.

5

10

[ °C ]

Pasteurisation

churning tempearture

time [ h ]

Crystallisation temperature

Crystallisation time

T

Figure 6: Temperature-time curve for making traditional sweet cream butter

Shortly before the churning process, the contents of the tank are mixed gently. On the other hand, the

agitator should only operate at selected intervals during the discharge phase. During the pasteurisa-

tion process, vacuum treatment can be used in order to remove negative flavours. These methods are

used in New Zealand and in the USA. The buttermilk fat content is around 0.2 to 0.3% higher due to

the unavoidable destruction of fat globules.

Special conditioning of the cream is necessary in order to improve the spreadability of the butter. A

special temperature-time program is used depending on the melting and solidification points of the fat.

After the pasteurisation process, the temperature of the cream is lowered to 5 - 6° C. The cream is

then allowed to stand for at least two hours, and its temperature is raised to approx. 18 - 21° C (de-

pending on the melting and solidification characteristics). This can be achieved by pumping the prod-

uct from the storage tank to the preheating tank via a plate heat exchanger. The cream is allowed to

stand for approx. 2 hours after the preheating process, and the temperature is then reduced to approx.

6° C in a plate heat exchanger.

11

The cream is allowed to stand for at least 12 hours in the tank before the churning process can be

commenced.

5

T

[ °C ]

Pasteurisation

Crystallisation temperature


10

20

min 2 h min 2 h min 12 h

time [ h ]

Figure 7: Temperature-time curve for cold-warm-cold crystallisation

12

2.4 Cream treatment for making sour cream butter

In the process used for making traditional sour cream butter, the creamery culture is added to the rip-

ening tanks.

5

T

[ °C ]

Pasteurisation

churning tempeartureCrystallisation temperature


10

20

min 12 h

Figure 8: Temperature-time curve for making sour cream butter

When it has been pasteurised, the cream is pumped to the ripening tanks with a temperature of ap-

prox. 18 - 20° C. The pH value is checked after the cultures have been added.

At a pH value of approx. 4.8 - 5.0, the acidification process is stopped by cooling the cream. The

cream tank is equipped with a corresponding heating and cooling device, a special agitator and a de-

vice for measuring the pH value.

2.5 Cream pre-heating

The crystallised cream is pre-heated to the appropriate temperature ahead of the buttermaking ma-

chine. In order to ensure that buttermaking processes are as efficient as possible, it is necessary to

avoid fluctuations of whatever nature.

Tests have shown that temperature fluctuations upstream of the buttermaking machine affect the wa-

ter content in the butter, even if all other parameters remain constant (fat content, speeds, butter tex-

ture, etc.).

13

The feed quantity to the buttermaking machine is maintained constant by means of a speed-controlled

displacement pump with a downstream inductive flow meter. Pressure-influencing factors from the

cream tank or gradually changing resistance levels at the cream pre-heater are compensated.

FIC TI

Icewater

Icewater

Cream 40%

TIC

TIC

Buttermilk

Steam 1,5 bar

Buttermilk

Condensate

Cream 40 %

Figure 9: Westfalia Separator cream pre-heater system

By integrating a cooling section, the pre-heating water can be set to and maintained at the desired

temperature at the start of production and during any interruptions of production. A cooling device for

recirculating the buttermilk is also integrated in the pre-heater.

2.6 Buttermaking machine

The WS buttermaking machine type BUD consists of the following main components:

• Primary churning cylinder with adjustable drive

• Secondary churning cylinder with adjustable drive

• Primary blender with adjustable drive

• Secondary blender with adjustable drive and vacuum section

• Vacuum unit

• Buttermilk recirculation and buttermilk cooling

• Butter granule recovery system

14

• Dosing unit for culture, salt and water

• Control system for production and cleaning

The treated cream is pumped from the cream tank to the primary churning cylinder via the cream pre-

heater at a constant rate. The rotating dasher shaft breaks down the fat globules, and so-called butter

granules form. The speed of the dasher shaft depends on the capacity, cream treatment, temperature,

etc., and can be adjusted by the operator.

Buttermilk cooler

Cream feed

Buttermilk

Butter granule recovery

Butter

Annular weir

Rotary screen

Figure 10: Butter granule recovery system

The mixture consisting of butter granules and buttermilk enters the secondary churning cylinder. The

mixture consisting of butter granules and buttermilk is cooled intensively by the addition of cooled

buttermilk (approx. 2° C). The cooling effect is intensified by a weir in the secondary churning cylinder

(WS patent).

The buttermilk is then separated in the secondary churning cylinder, and is then conveyed directly to

the buffer tank.

The butter granules enter the texturizer and are conveyed to the blending section with augers. Butter-

milk is removed and recycled to the secondary churning cylinder via a centrifugal pump. Fine butter

granules from the texturizer can thus be directly recycled into the process.

The additive components such as cultures, salt or water are added in the blending section.

15

A vacuum section installed between the primary blending section and the secondary blending section

reduces the air content to less than 0.5%.

The integrated displacement pump in the secondary blender (WS patent) produces a high vacuum

which removes almost all of the air enclosed in the butter.

The butter is blended intensively in the second blending section. Fine water distribution of 3 - 5 µm

can be achieved in this way, and the butter is subsequently conveyed to a butter tank.

2.7 Dosing station

Depending on the particular capacity and task involved, the dosing station consists of two or three

dosing pumps. Each dosing pump is monitored and controlled by an inductive flow meter.

FIC

FIC

FIC

culture 2 / saltbrine

culture 1 / saltbrine CIP

water

Figure 11: BDSB dosing station

A calculation program integrated in the operating monitor calculates the dosing quantities on the basis

of the capacity of the buttermaking machine, and uses these quantities as the preset data for the

pumps. The dosing quantity is automatically changed if the capacity is increased or reduced. This is

particularly important in the case of cultures, as any analysis will only produce useful results several

days later.

16

The tanks are equipped with agitators and level sensors so that the addition of culture, saline solution

or water can be automatically requested.

Cream flow to BUD

Buttermilk fat contentCream fat contentDosing quantity per pump

Butter capacity in kg/h

Computer

BUD

Dosing pump 1 Dosing pump 3Dosing pump 2

Flow meter Flow meterFlow meter

Water

Water

Culture IICulture I

Salt brine Salt brine

Figure 12: Functional diagram of the dosing station

2.8 Control

The buttermaking machine is adjusted to meet the various process parameters via frequency-

controlled drives.

In addition to the external motor control, the machine has a control system consisting of the following:

Siemens S5 135U programmable logic controller

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Equipped with:

• CPU 528 / communication processor CP 527

• Digital inputs / digital outputs

• Analog inputs / analog outputs

Monitoringand

Control

Colour graphic displayOperator interface

��

��

��

��

��

Printer

CP 527 / CP 528

Siemens S 5

DA / DE AA / AE

Option:

Control unit

Process

230 V AC

24 DC

M3 ~

4-20 mA

MCC

Tem

per

atur

e p

robe,

Flo

w m

ete

r, e

tc.

Mod

ulatin

g v

alv

es

Drives

Aut

omatic

val

ves

Fee

dback

Figure 13: Structure of control system

Operating monitor

Siemens MP 14

Equipped with the following:

• Colour monitor 14 inch

• Function keys F1 - F16

• Operating keyboard for selecting images and entering data, etc.

18

The screen installed in the front of the buttermaking machine enables the process to be displayed in a

clear manner.

The system provides process automation functions for measuring, controlling and regulating data as

well as screen-oriented operating and monitoring functions.

The entire process is observed with the aid of process-related flow diagrams. The operator can thus

monitor the process, obtain an overview of the system status at all times and thus identify the occur-

rance of any problems. Simple user guidance and function keys permit rapid operator intervention in

the event of any problems.

2.9 Butter distribution

The butter is generally distributed to the packing machines from a butter tank with attached butter

pumps.

Packing machines usually operate with a direct feed facility, which then require a directly assigned

butter pump.

In order to prevent product damage, Westfalia Separator has developed a system for reducing butter

overworking in butter tanks (WS patent).

The handling capacity of the packaging machines determines the speed of the butter pumps, and the

speed of the pumps in turn controls the speed of the screws in the butter tank.

This arrangement achieves optimum pressing ahead of the butter pump as well as gentle product

handling.

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Water

steam

CIP- Return

CIP- Feed

Butter siloButter pump

Packaging machine

Figure 14: Installation diagram of a butter silo

2.10 CIP system

The process concepts of Westfalia Separator AG include not only the buttermaking systems but also

cleaning systems whereby the cleaning lye is recycled.

Larger quantities of CIP liquid are required when butter distribution systems are integrated.

The CIP system features a hot water tank for the necessary rinsing processes, a lye tank for the spe-

cial cleaning liquid, the necessary valves, the heating system with the corresponding pumps.

A storage tank can be used for treating residual fat. The storage tank then collects and decants the

residual fats from the melting process and the initial rinsing stage. The concentrated fat is used in

other processing processes.

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Steam Steam

SteamCo

nde

nsa

te

M

Water CausticButter-

oil

Water

CIP- Return

CIP-Feed

CIP

Figure 15: CIP system

2.11 Reworkers

Westfalia Separator has developed a reworker for treating block butter.

This machine has been designed for reworking block butter. Intensive blending is necessary before

the butter is packaged in consumer packagings. The reworker type BMB 2500 enables salt, water and

other soluble additives to be added to the butter.

The block butter is stored in cold rooms at -10°C to -20°C. A subsequent controlled conditioning proc-

ess raises the temperature of the butter to approx. +2°C to +4°C before the butter is conveyed to the

reworker type BMB 2500.

The packaging material is removed, and the butter blocks are pushed onto the elevator.

21

Figure 16: Reworker

The main cylinder conveys the block to the inlet of the reworker. The swivel cylinder tips the block

onto the inlet chute.

There is a conveyor screw with adjustable drive in the hood or inlet chute. The supply speed of the

screw determines the capacity of the reworker type BMB 2500.

The cutter drum is equipped with replaceable cutters, and cuts the block into small pieces.

The conveyor screws in the reworker convey the butter pieces to the blending section, where the but-

ter is intensively blended. The mechanical work raises the temperature of the butter to approx. 8° C to

10°C.

Salt, water or soluble additives can be added in the blending section. The blended butter is discharged

from the machine via an extension tube, and can be conveyed to a butter tank for distribution to sev-

eral packaging machines or to a directly connected packaging machine.

22

2.12 Special processes for the production of milk fat products

This buttermaking machine can be used for making milk fat products with different compositions.

The production of fat-reduced milk and mixed fats has been started in response to consumer demand.

2.12.1 Milk fat with reduced fat content

The buttermaking machine can be used for making milk fats with a fat content of max. 60%.

Suitable additives can be used for reducing the fat content. These additives and products are added in

the blending section of the texturizer.

The production and composition of the additives for so-called half-fat butter are of vital importance for

successfully marketing these products.

Cream 40 %

Cream treatment

Cream storage

Cream preheating

Buttermaking machine

Butterdistribution

Butter packaging

Storage

BDSB Dosing system

Pasteurisation

Dosing media treatment

CIP - System

Butter with60 % Fat

Figure 17: Production of butter with reduced fat content

23

2.12.2 Butter with vegetable fat additives

Improved spreadability can be achieved by the addition of vegetable oils.

The buttermaking machines can be used for this process without the need for major inversion. The

vegetable fat content in relation to the total fat content is generally 25%. The vegetable fat is added to

the cream before the cream treatment process.

Cream 40 %

Pasteurisation

Crystallisation

Vegetable oil

Cream preheating

Primary churning cylinder


Secondary Churningcylinder

Texturiser II

Texturiser I

Butter distribution

Packaging machine

Buttermilk Separator

Butter milk

Butter with vegetable oil

Dosing system

Figure 18: Production of butter with the addition of vegetable fat

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2.12.3 Butter production with reduced content of solids non fat

Certain regions require butter to be made with a reduced content of solids non fat (SNF).

Cream 40 %

Cream treatment

Cream storage

Cream pre - heating

Primary churning cylinder


Secondary churning cylinder

Texturiser II

Texturiser I

Butterdistribution

Butter with < 1 % SNF

BDSB Dosing system

Salt brine preparation

Cooling water

CIP - System

Figure 19: Butter production with reduced SNF content

Washing is necessary in order to achieve an SNF content of less than 1%. Whereas this did not pres-

ent any problems in the past when butter vats were used, the current use of continuous buttermaking

machines means that SNF reduction can only be achieved at the expense of certain compromises.

Westfalia Separator has developed a special process for making "table butter" in India. The special

washing process used in this system achieves an adequate reduction in the SNF content.

25

The washing effect is influenced by the way in which the wash water is added to the system. The tem-

perature of the wash water is also very important.

26

3 Butteroil production (AMF)

3.1 Introduction

Westfalia Separator has been manufacturing separators for more than 100 years and decanters since

1959 for the most diverse processes in the dairy industry. These separators and decanters are often

the very heart of the process.

The product, anhydrous milk fat (AMF), butteroil or dry butter fat, which is known in Asia under the

name "Ghee", is widely used for the recombination of milk and milk products, as a frying fat and as a

raw material for other food factories, for example in the baking industry.

Increasing industrialisation in many countries on the one hand and the population explosion, for ex-

ample in third-world countries on the other have given this product a new dimension. Its many uses

and excellent storage characteristics have lent impetus to the development of new processes for the

production of anhydrous milk fat.

Many years of experience in the design of separators and decanters as well as fundamental knowl-

edge of the technologies involved are the corner stones of the expertise and knowhow of Westfalia

Separator AG. The supply of complete plants for the production of anhydrous milk fat (AMF) is a logi-

cal consequence of this development.

3.2 Chemical/physical correlations

For the sake of simplicity, only the production of AMF (AMF = Anhydrous Milk Fat) is described here,

whereby the general collective term "butteroil" is used as a rule for the end product.

Definition:

Butteroil is a product which is obtained exclusively from milk, cream or butter by the almost complete

removal of water and fat-free dry matter. (1)

27

The current international specifications are set out in the following:

Definition of product Water-free milk fat (anhydrous

milk fat) AMF made from top

quality milk, cream or butter and

to which no neutralising sub-

stances are added.

Water-free butter fat (anhydrous

butteroil) made from cream or

butter of any age.

Dry butter fat (butteroil) made

from cream or butter of any age.

Composition

Milk fat 99.8 % minimum 99.8 % minimum 99.3 % minimum

Water 0.1 % maximum 0.1 % maximum 0.5 % maximum

Free fatty acids 0.3 % maximum 0.3 % maximum 0.3 % maximum

Copper 0.05 p.p.m. maximum 0.05 p.p.m. maximum 0.05 p.p.m. maximum

Iron 0.2 p.p.m. maximum 0.2 p.p.m. maximum 0.2 p.p.m. maximum

Peroxide 0.2 milliequivalent O2/kg

fat

0.3 milliequivalent O2/kg

fat

0.8 milliequivalent O2/kg

fat

Coliforms Negative/ g Negative/ g Negative/ g

Taste and texture Pure and mild

(at 20 - 25 °C)

No pronounced impure or

in any other way imperfect

taste or aroma

No pronounced impure or

in any other way imper-

fect taste or aroma

Neutralising substances None Traces Traces

Table 1

3.2.1 Definition and designation of milk fat

As a substance of biological origin, milk fat is a complex mixture of several components which differ

only slightly in terms of their characteristics. Triglycerides are the main component in milk fat.

Triglycerides are esters of the three-valent alcohol glycerine with monocarboxylic acids.

A uniform designation of fats is not always encountered in literature. The designations fats, lipids, lip-

ines or fatty oils are used for the same group of substances.

For this reason, it is necessary to define some concepts. Lipids is the term used to describe the entire

group of substances.

In general, we distinguish between the following:

• simple lipids

• compound lipids (also known as lipoids ) and

• lipid derivatives.

Simple lipids are esters of fatty acids with alcohols.

28

Milk fat

Simple lipids Compound lipids Lipid derivatives Fat escort substances

Glycerides Phospholipids Free fatty acids Stearins

Table 2: Overview of components in the milk fat complex

These include fats as esters of the monocarboxylic acids with glycerine and waxes as esters of mono-

carboxylic acids with high molecular alcohols. Compound lipids contain alcohol and monocarboxylic

acids as well as other components. These include the phospholipids and glucolipids. Lipid derivatives

are substances which are obtained from simple and compound lipids in the course of chemical proc-

esses and which feature the general characteristics of the lipids.

Depending on the particular origin, we distinguish between animal and vegetable fats. However, a

useful method is to classify food fats into vegetable fats, animal deposit fats and milk fats. The distinc-

tion drawn between milk fat and animal deposit fats emphasises the particularly nutritional value as

milk fat is the only natural fat which is formed in the milk glands and used exclusively for nourishing

the young. The term oils is used to describe simple lipids which are liquid at room temperature. As

however solid fats liquefy when their temperature is raised, the term oil is not justified. Every fat can

be an oil, and every oil can be a fat.

The term oil is also used to describe liquid hydrocarbon mixtures. In order to make a distinction, liquid

lipids are described as fatty oils. We also speak of etherl oils, such as rose oil and orange oil, which

are used as scents. Fats can be recognised by the fact that they leave a permanent mark on paper,

whereas the marks of ethere oils evaporate after a certain amount of time. They produce water-

soluble soaps with potassium lye. On the other hand, crude oil components do not react and remain

insoluble in water. When heated to more than 300° C, fats give off acrolein, which is a pungent sub-

stance which irritates the eyes. Various designations are used for milk lipids, e.g. milk fat, butter fat,

whey fat or cheese fat, and the designation is based on the particular product which is contained in

the fat or from which it is isolated. Although milk is the starting substance for all products, this distinc-

tion may be appropriate. The designations are used for describing the possible effect which the proc-

essing method may exert on the characteristics and the composition of the milk fat in the products, as

there are differences in the composition in comparison with the fat contained in raw milk.

Pure fat is a mixture of triglycerides.

Milk fat occurs in milk in the form of small fat globules with a diameter of 3 ... 6 µm, and forms an

emulsion with water of the type oil in water. In order to stabilise the emulsion, the fat globule is sur-

29

rounded with an adsorbent envelope consisting of phospholipids and proteins. The envelope contains

fat escort substances.

The components of the milk fat are contained in various phases, namely the fat globule and the enve-

lope; there are also traces in the milk serum.

Table 3 sets out the components of milk fat and their quantities in the individual phases of milk.

Lipid Contents Quantities Occurance

Simple lipids Triglycerides

Diglycerides

Monoglycerides

Waxes

98...99 %

0.2... 0.6 %

0.02 %

Traces

Fat globules

Fat globules

Compound lipids Phospholipids

Lecithin

Kephaline

Sphingomyceline

0.2...1.0 %

35...40 %

29...38 %

19...24 %

Fat globule envelope and

serum

Lipid derivatives

Fat escort substances

Fatty acids

Sterines

Cholesterol

Lanosterine

7-dehydro-

cholesterol

Squalene

Fat-soluble

Vitamins

Vitamin A

Carotinoides

Vitamin E

Vitamin D

Vitamin K

Traces

0.25 ... 0.40%

0.2 ... 0.4%

Traces

Traces

Traces

Traces

7.0 ... 8.5 µg

per 1 g Fat

8.0 ... 10.0 µg

per 1 g Fat

2.0 ... 50 µg

per 1 g Fat

Traces

Traces

Fat globules and serum

Aqueous phase

Fat globules

Fat globules and envelope

Table 3: Components of milk fat (according to Jenness-Patton ..[..])

The data concerning the content of individual phospholipids are calculated in the form of lecithin on

the basis of phosphorus content.

30

The milk fat components are also classified on the basis of a typical reaction for esters, namely

saponification.

Saponification is the process whereby esters are split by alkalis into alcohol components and the alkali

salts of monocarboxylic acid.

Milk fat components are classified into saponifiable substances and non-saponifiable substances (ta-

ble 4).

Milk fat

Saponifiable substances Non-saponifiable substances

Triglycerides

Mono- and diglycerides

Lecithin

Cephalin

Sphingomyelin

Free fatty acids

Cholesterol

Lanosterin

Fat-soluble vitamins

Squalene

Table 4: Saponifiable and non-saponifiable substances in milk fat

Although free fatty acids are not subject to saponification according to the above definition, they bind

alkalis and are considered to belong to the saponifiable components of milk fat.

Under certain conditions, the non-saponifiable substances do not react with the alkalis. During the

saponification process, substances which are soluble in water and insoluble in etherl oils are obtained

from the saponifiable components. The aqueous soap solution which is obtained is extracted under

specific conditions with diethyl ether (ethoxyethane).

The non-saponifiable components of the milk fat are the dried ether extract obtained from boiling the

0.5 N aqueous soap solution containing KOH for one hour. The content is 0.30 ... 0.45% of total fat.

• As illustrated by the table, triglycerides make up 99 % of the mass of the milk fat. Their

characteristics primarily determine the reaction of the milk fat and the characteristics of

fatty products.

31

3.2.2 Characteristics of fatty acids

Saturated fatty acids

The saturated fatty acids contained in milk fat are significant for the following:

• Melting behaviour and thus consistency

• Characterisation of the milk fat and

• Taste and aroma.

Saturated fatty acids with up to eight carbon atoms in their molecules are liquid at room temperature.

The higher molecular acids are white, crystalline compounds.

The melting points increase in line with rising relative molecular mass. The fatty acids with an odd

number of carbon atoms have a lower melting point than fatty acids with one carbon atom less. If the

melting points of the even-number fatty acids and the odd-number fatty acids are set out separately

against the number of carbon atoms, we achieve two almost parallel curves, as can be seen in the

diagram. The abnormally high melting points of the acids of C1 to C5 can be explained by the asso-

ciation to dimers as a result of hydrogen bridge binding. The chain length also has an effect on the

other physical characteristics. The effect of the chain length is greater with the saturated fatty acids

than with the unsaturated fatty acids. As the chain length increases, the melting points and density

rise, whereas dissociation and acid strength decline. Unlike all other fatty acids of milk fat, butyric acid

is completely soluble in water, and capronic acid is partially soluble in water. Both acids can thus be

titrated with bases in aqueous solution. This property is the basis for determining a fat coefficient,

namely the Reichert-Meißl coefficient. The lower molecular fatty acids, including the caprinic acids,

are volatile with steam. The number of fatty acids which are volatile in steam but insoluble in water

produces another fat coefficient, namely the Polenske coefficient. All fatty acids are soluble in the typi-

cal organic solvents alcohol, ether, petroleum ether and benzene. They are thus also detected with

the fat determining methods which are based on extraction.

Free low molecular fatty acids have the greatest effect on the taste and aroma of milk fat. The lower

volatile fatty acids have an unpleasant rancid and sweaty taste and aroma which are still perceptible in

concentrations of 0.009 mg acid per 1 kg fat. Every violation of this limit concentration has a negative

effect on the taste of the milk fat, and thus diminishes the quality of the product. In quantities below the

limit concentration, the low molecular fatty acids however contribute to the aroma of certain dairy

products. Fatty acids with more than 12 carbon atoms are virtually without taste and without aroma.

The chemical reactions concentrate on the functional carboxyl group and, under special conditions,

also on the carbon chain.

The ability to bind bases is used to determine specific quantities for calculating the degree of acidity in

butter fat. The carbon chain is stable with respect to oxidation effects to which it is exposed under the

normal processing and storage conditions of milk and dairy products. The stability is comparable to

32

that of alkanes. Pyrolysis phenomena do not occur. However, enzymes formed by the catalytic influ-

ence of fungi may be less efficient than saturated fatty acids due to the air oxygen of ß-oxidation.

ß-oxidation is defined as the process whereby fatty acids oxidise to methylketone which has one car-

bon atom less at carbon atom 3 via a ß-keto acid as intermediate product.

3.2.3 Phase inversion

In its normal state, milk fat forms a stable emulsion with water of the oil-in-water variety. To stabilise

the emulsion, the fat is enveloped in an adsorptive covering of phospholipids and proteins.

The break-down of this emulsion and separation of all non-milk-fat components is the aim of butteroil

production.

MI

MI

MI

MI

lipop

hil

hydr

ophi

l

= water

= Euglobolin layer

= Lipoid layer ( lecithin )

= liquid fat nucleus

= crystalliszed triglyceride layer

1

2

Cu++

Cu++

Fe++

Cu++

Fe++ 3

MI = Membranlipase

4

Cu++

( 1 ) = triglyceride molecules

( 2 ) = Phosphatide molecules

( 3 ) = Euglobulin molecules

( 4 ) = Microsomes

Cu++ = adsorbed copper ions

Fe++ = adsorbed iron ions

Figure 20: Diagram of the structure of a fat globule and its envelope

It is possible to break down the membrane by means of mechanical energy or a chemical reaction.

Mechanical energy (e.g. homogenisation) is used to break open the membranes. Smaller fat globules

are formed by the newly created membranes, which themselves were created by the fragmentation of

the original membranes and from the proteins in the milk serum.

33

Reduction of the fat globules is also employed, for example, in the processing of drinking milk, in order

to prevent the so-called "creaming" effect.

Figure 21 attempts to illustrate the principle of homogenisation.

d1

d2

Fat globule formed fromthe available envelopematerial

fat globule formed from the envelopematerial of the serum

Figure 21: Graphic representation of the principle of homogenisation

The following calculation contains a key statement for the production of butteroil.

Assumption:

Existing fat globule size d1 = 3 µm

Desired fat globule size d2 = 1 µm

34

Calculation of the volume:

1

3

2

3

1 2

13

23

63

6

27

6

61

6

1

6

27

V

V

V V

d

d

n

= =⋅

=⋅

= =⋅

=⋅

= ⋅

=

⋅

⋅

n

π π π

π π π

27 fat globules with a diameter of 1 µm can be formed from one fat globule with a diameter of 3 µm .

Surface calculation:

1 12 2

2 22 2

1 2

3 9

1 1

9

O

O

O O

d

d

n

= ⋅ = ⋅ = ⋅

= ⋅ = ⋅ = ⋅

= ⋅

=

n

π π π

π π π

Theoretically, the surface of a fat globule with a diameter of 3 µm can only cover 9 fat globules with a

diameter of 1 µm. Therefore, for 18 further fat globules of the same size, the membranous material

must be taken from the serum.

However, the aim in the production of butteroil is not to reduce the size of the fat globules; on the con-

trary, the aim is to destroy the membranes or envelopes so that the fat can be recovered. It is there-

fore important to prevent the formation of fat globules with intact new membranes.

An initial conclusion from the above is that the amount of serum should be minimised before the start

of actual production of the oil, so as to minimise the amount of available membrane building blocks.

In order therefore to achieve adequate release of fat, a cream fat content of greater than 75% is re-

quired. The release of the fat, and the phase inversion brought about by this, take place by mechani-

cal fragmentation of the intact fat globules in a homogeniser.

Figure 22 illustrates the principle of phase inversion.

35

d1 Fat globule formed fromthe available envelopematerial

d2

Free fat resulting from the absence of envelopematerial

Figure 22: Graphic representation of the principle of phase inversion

The graphic representation itself illustrates that there is still a part with intact fat globules.

100

80

60

40

20

10 20 30 40

Pha

se in

vers

ion

( %

)

ATF ( % )

= 78 % initial fat content



Pressure : 70 barTemperature : 55 °C

Figure 23: Phase inversion as a function of the homogenisation pressure (bar)

Steps for optimisation of phase inversion can be derived from figures 23 and 24 (3).

36

Complete phase inversion is therefore not possible with this process. Furthermore, a relatively stable

emulsion layer is formed from the existing amount of cream and part of the serum; this impedes

separation as a third layer between the oil and serum phases.

Special measures are necessary if the reversible process of formation of new, intact fat globules is to

be minimised.

100

80

60

40

20

35 90 140

Pha

se in

vers

ion

( %

)

Homogenisation pressure ( bar )

= 78% initial fat content


ATF : 30 %Temperature : 58 °C


Figure 24: Phase inversion as a function of the initial ATF

(ATF = Amount of free fat in the total fat)

37

Recirculationfrom Cream concentrate to Oil concentrator

Figure 25: Phase inversion

The optimum parameters for homogenisation pressure shown in figures 23 and 24 and the initial fat

content and ATF (4), when applied to phase inversion give a degree of inversion of 80 - 95 %.

The ATF, which contributes considerably to the efficiency of phase inversion, is increased en-route to

the homogeniser by means of recirculating a partial stream of the product leaving the homogeniser.

Accordingly, the capacity of the homogeniser must be designed for third the capacity of the oil

throughput of the butteroil plant.

3.2.4 Minimising the emulsion phase

The following applies for minimising the emulsion content:

The three fractions, namely fat, phospholipids and proteins, are largely responsible for a stable emul-

sion. If one of the three fractions is removed, or is changed to such an extent that it can no longer be

used as a building block for the membranes, then the formation of intact fat globules is prevented and

the formation of emulsion is not possible.

If, for example, the proteins are converted from their natural state into a denaturated state, then they

are no longer suitable as a building block for the envelope.

For example, with acid (product pH value: 4.5 - 4.7) or lye (pH value 10 - 11), the hydrate envelope of

the protein is weakened. This allows the approach of various protein molecules. By means of so-

38

called hydrogen bridge formation, they join together and form high-volume groups of protein mole-

cules. These flocculant-like solids can be separated out because their specific weight is greater than

that of the oil.

3.2.5 Reducing the free fatty acids

FFA (= Free Fatty Acids) in the end product oil results as a rule in a loss of quality. Furthermore, IDF

standards place a limit on the FFA content (figure 1). If the FFA content is to be reduced, e.g. because

the initial values are too high, this can be achieved by physical and chemical means.

Free fatty acids are short-chain fats, such as butyric acids, caproic acids and carpinic acids. There are

problems of taste (rancidity) and/or aroma if the above are present in sufficient concentrations.

Free fatty acids result from the process whereby lipase enzymes adhere to the fat globule membrane

and break down free fat over a period. It is necessary to consider that the activity of the enzyme is

very slow at low temperatures. Its maximum activity is at about 37° C. Above 50° C, its activity is

minimal, and its activity stops completely at higher temperatures (> 60 °C) (4). Assuming that there

may be a relatively high FFA content in the initial product, namely cream and butter, it may be neces-

sary to take special measures in order to remove the free fatty acids from the product.

A saponification process can be used to reduce the FFA content.

Addition of lye (product-pH-value > 11) causes the free fatty acids to "saponify".

The resulting flocculate can then be separated out in the centrifuge.

3.2.6 Peroxide number

The quality of the butteroil is also determined by the peroxide number which expresses the millie-

quivalents of oxygen O2 bound by peroxide in one kilogram of oil.

Oxidation of fat that has already occurred cannot be reduced as a rule; however, it can be suppressed

or kept constant for a certain length of time. This is achieved by the addition of so-called antioxidants.

39

3.2.7 Phospholipid distribution

During centrifugal separation of the product, most of the free phospholipids migrate into the serum.

For this reason, it is necessary to calculate the content of phospholipids in order to determine the yield

of the "heavy phase" from a butteroil process.

An important criterion during the production of butteroil from cream is the heavy phase or buttermilk. In

addition to the familiar process, Westfalia Separator has now developed a new process and has

launched this new process on the market. The requirement that as much secondary skim has also to

be produced when butteroil is being manufactured means that, during cream concentration, it is pos-

sible to produce a milk which is similar to normal skim milk and which guarantees a higher yield when

mixed with other products.

The phospholipid content in this skim milk coming from the cream concentrator is slightly higher in

comparison with the content in normal skim milk. This higher phospholipid content also has an effect

on the yield and suitability for skimming.

The buttermilk in this process is known as ß-serum.

The following section details the phospholipid distribution in the processes butteroil production from

cream (standard process) and butteroil production from cream with secondary skim and ß-serum.

40

Phospholipid distribution in butteroil/AMF production

Buttermilk 0,5 % Fat0,2-0,3 % Phospholipids

Rahmkonzentrat 75 %Fat0,8-1,0 % Phospholipids

Process with Secondary skim and ß-Serum

Secondary skim 0,2 % Fat0,08 % Phospholipids

Butteroil 99,9 % Fat

ß-Serum 1,5 % Fat0,8-1,0 % Phospholipids

Skim milk 0,06 % Fat0,017 % Phospholipids

Rahm 35 %Fat0,175 % Phospholipids

Cream concentrate 75 %Fat0,8-1,0 % Phospholipids

Butteroil 99,9 % Fat

Raw milk 4 % Fat0,035 % Phospholipids

Standard process with Buttermilk

Figure 26: Phospholipid distribution

Because of its high phospholipid content, the ß-serum is very appropriate for emulsion processes or

other special products.

41

3.3 Processes used for production of butteroil

Butteroil can be made from butter and from cream. Whereas in the past, butteroil used to be made

almost exclusively from butter, the situation nowadays has changed, and cream is used instead of

butter.

It is now necessary to design installations which are capable of processing all raw products.

The following diagram illustrates the spin samples of various butter types and phase-converted cream.

Cream 80 %pH 6,8

phase inverted

102030405060708090

100

5

1

0,1

Sweet cream butterpH 6,5

102030405060708090

100

5

1

0,1

Sour cream butterpH 4,5

102030405060708090

100

5

1

0,1

Sweet cream butteradjusted to

pH 4,5 with acid

102030405060708090

100

5

1

0,1

Clear Oil

Emulsion

Serum

Sediment

Figure 27: Spin samples of various raw products

As can be seen in figure 27, processing of sour cream butter is the easiest at first glance, and can be

carried out with minimum fat losses as a clear separating line occurs between the oil and serum

phases.

The separation of oil, emulsion and serum from one another rarely takes place in static sedimentation

tanks. As a rule, separation is far more efficient in high-capacity self-cleaning separators and/or con-

tinuously operating three-phase decanters. The emulsion phase is an intermediate layer, and poses

major problems during the separation procedure; the problems can only be solved by modifying the

design of the centrifuges.

Planned losses can be minimised by using suitable separators and decanters adjusted for the par-

ticular separation function required.

Extremely precise designs can be achieved nowadays by means of computer-aided volume controls.

42

3.3.1 Standard process using buttermilk

Pasteurised cream in which the lipase enzyme has been inactivated should be used for producing

butteroil from sweet cream. This is achieved by the application of a recognised cream heating proc-

ess.

Pasteurisation

Cream concentration

Phase inversion

Oil concentration

Oil polishing

Cream 40 %

Skimming

Butter milk

Washwater

Vacuum treatment

Butteroil > 99,8 %

Washwater

Figure 28: Block diagram for making butteroil from cream with buttermilk

In the case of the process version illustrated in figure 28, butteroil is produced from cream of about

40%. "Buttermilk" is also produced in this process. The "buttermilk" discharging from the process,

namely about 60% of the cream feed, contains all the phospholipids which are to some extent only

released during phase inversion.

43

1 2 3 4

5 6 7 8

Butteroil (AMF)Buttermilk

Cream 40 %

1 Cream balance tank 5 Buttermilk separator

2 Cream concentrator 6 Buttermilk balance tank

3 Homogeniser 7 Polishing separator

4 Oil concentrator 8 Vacuum dryer

Figure 28.1: Flow diagram for butteroil production from cream with buttermilk

Sweet cream of approx. 40% is heated to approx. 55 - 60 °C in a plate heat exchanger. This tem-

perature is necessary to ensure that the cream to be concentrated remains liquid in the separator

bowl.

The cream is concentrated to 75 - 78 % in the cream concentrator and conveyed to the buffer tank of

the homogeniser.

The phase inversion process takes place under high pressure. The temperature, cream concentration,

recirculation quantity, pressure and aspects such as the design of the buffer tank are very important

aspects in this respect.

The emulsion and serum phase (heavy phase) is separated from the oil (light phase) in the down-

stream oil concentrator.

The oil with a concentration of 99.5% is heated in the plate heat exchanger to 90 - 95 ° C.

Oil washing or FFA reduction can be achieved by integrating an oil polishing separator.

The remaining moisture is evaporated in the vacuum evaporator, and the butteroil leaving the vacuum

evaporator has an oil content of more than 99.8%. The "heavy phase" discharging from the oil con-

centrator is recycled back into the buffer tank of the cream concentrator; it is then separated again and

concentrated.

44

The heavy phase from the cream concentrator is skimmed in the skimming separator. The cream re-

covered from the skimming separator is also recycled back into the process. The heavy phase leaving

the skimming separator must be described as buttermilk as it contains all the phospholipids.

3.3.2 Process using ß-serum and secondary skim

As already described above in the standard process, pasteurised cream is normally used.

The main difference with respect to the standard process is to be seen in the fact that the serum

phases are recycled, as the phospholipids are released from the fat globule membranes during the

phase inversion process.

Pasteurisation

Cream concentration

Phase inversion

Oil concentration

Oil polishing

Cream 40 %

Separation

Secondary skim

Washwater

Vacuum drying

Butteroil > 99,8 %

Separation

ß - SerumWashwater

Figure 29: Block diagram making butteroil from cream with ß-serum and secondary skim

Sweet cream of approx. 40% is heated to approx. 55 - 60 °C in a plate heat exchanger. This tem-

perature is necessary to ensure that the cream to be concentrated remains liquid in the separator

bowl.

45

The cream is concentrated to 75 - 78% in the cream concentrator and conveyed to the buffer tank of

the homogeniser. The discharged skim milk (secondary skim) can be separated again if it is required.

1 2

Skimmilk

5

3

7 86

Butteroil (AMF)

4

Buttermilk

Cream 40 %

1 Cream balance tank 5 Buttermilk separator

2 Cream concentrator 6 Buttermilk balance tank

3 Homogeniser 7 Polishing separator

4 Oil concentrator 8 Vacuum dryer

Figure 29.1: Flow diagram for butteroil production from cream with ß-serum and

secondary skim

The phase inversion process takes place under high pressure. The temperature, cream concentration,

recirculation quantity, pressure and aspects such as the design of the buffer tank are very important

aspects in this respect.

The emulsion and ß-serum (heavy phase) is separated from the oil (light phase) in the downstream oil

concentrator.

The oil with a concentration of 99.5% is heated in the plate heat exchanger to 90 - 95 ° C .

Oil washing or FFA reduction can be achieved by integrating an oil polishing separator.

The remaining moisture is evaporated in the vacuum evaporator, and the butteroil leaving the vacuum

evaporator has an oil content of more than 99.8%.

The "heavy phase" discharged from the oil concentrator is pumped to a separate buffer tank. The

"heavy phase" is now concentrated in a separator to approx. 65% to 75% fat content, and is recycled

to the buffer tank of the homogeniser.

46

The ß-serum discharging from this separator contains the remaining phospholipids.

3.3.3 Processes for butter processing

With butter as the initial product, the emulsion of water in oil is already present. Phase inversion will

have taken place during the churning process.

The initial product is of decisive importance for the design of the installation. Basically, an installation

for processing cream is also suitable for the separation of melted butter.

When sweet cream butter with a pH of around 6.5 is to be processed and no "chemical agents" (e.g.

citric acid) are allowed to be used for denaturating the proteins, the emulsion layer has to be taken

into account. Centrifugation and destruction of this layer can only be carried out by specially designed

separators and phase inversion. The operating method of the separator has a decisive influence on

the process, the required additional equipment and the efficiency of the installation. For processing

sweet cream butter, it is necessary to use a separator which allows concentration to 99.5% fat. The

emulsion has to be discharged with the serum phase.

When sour cream butter with a pH of 4.6 to 4.5 and with an increased protein content is to be proc-

essed, a decanter can be used. Separate concentration of the solids is possible.

In any case, a separator (polishing separator) has to be installed downstream of the decanter to in-

crease the fat concentration to 99.5%.

A polishing separator is necessary for butter processing and for FFA reduction. High solids contents

can reduce the capacity and efficiency of the installation as frequent partial solids ejections of the

separator bowl are required.

47

3.3.3.1 Melting the butter blocks

The raw product, namely butter, will usually have been kept in cold storage at -18 to -20° C in 20 or 25

kg blocks, before being further processed into butteroil. Frequently, the butter coming from cold stor-

age is intermediately stored in order to raise the temperature by ambient air to >0° C. The butter is

then melted in one of a variety of steam-heated systems on the market. In order to eliminate costly

conditioning and the disadvantages of the steam-heated melting system, Westfalia Separator has de-

veloped the BMSA 5000 butter melting system.

The main advantages of the described system are very efficient use of energy and the very gentle

melting process. This also results in the fact that the protein in the butter is not locally overheated, and

protein burning also does not occur. The protein obtained in this oil production method has a higher

quality for subsequent use.

3.3.3.2 Making butteroil from sweet cream butter

The butter blocks are taken from cold storage at, for instance -20° C, and are melted in the melting

system. The product temperature in the buffer tank, depending on the design of the plant, is between

45 and 65°C. The temperature of the product is raised to 70 - 75 °C in a plate heat exchanger.

Phase inversion by means of a homogeniser is required to minimise the emulsion phase. The oil con-

centrator, a separator with disc type bowl, achieves separation of 99% to 99.5% fat. The heavy phase,

a mixture of buttermilk and residual emulsion particles, is fed to a skimming separator.

The oil phase (light phase) is heated to about 90° C and then separated again in a further separator.

Before the oil is fed to the polishing separator, wash water is added to improve the quality of the oil.

48

Butter melting

Butter

Phase inversion

Oil concentration

Oil polishing Buttermilk

Washwater

Vacuum drying

Butteroil > 99,8 %

Skimming

Washwater

Figure 30: Block digram for making butteroil from sweet cream butter

In the downstream vacuum evaporator the residual moisture content is adjusted to less than 0.1%.

The efficiency of the installation depends on the degree of skimming of the heavy phase discharging

from the oil concentrator and the oil polishing separator. The cream should have a fat content of 65%

to 70% for optimum phase inversion in the homogeniser.

49

4

2

6 75

Butteroil (AMF)

3

Buttermilk

1

1 Butter melting system

2 Homogeniser

3 Oil concentrator

4 Buttermilk separator

5 Buttermilk balance tank

6 Polishing separator

7 Vacuum dryer

Figure 30.1: Flow diagram for butteroil production from sweet cream butter

3.3.3.3 Processing of salted sweet cream butter

The amount of salted butter used as a raw material for the production of butteroil in recent years has

risen steadily. The salt content is removed together with the buttermilk during centrifugal separation.

The salt concentration in the buttermilk increases to approx. 10% if the original salt content of the

butter was 2% for example. Further processing of the salted buttermilk is limited.

For this reason, the emulsion phase in salted sweet cream butter can also be "broken" by the addition

of citric acid. At the same time, the protein in the butter is denaturated. The treated raw material then

behaves in the same way as sour cream butter.

50

Butter melting

Butter

Reaction tube

Oil concentration

Oil polishing

Washwater

Vacuum drying

Butteroil > 99,8 %

Addition of Acid

Serum

Washwater

Figure 31: Diagram of the processing of salted sweet cream butter

The melted butter is brought to a pH of 4.5 - 4.6 by the addition of acid. At this pH, not only the free

protein is denaturated; in addition, due to the alteration in the intact fat-globule membrane protein, the

membrane is broken open and the emulsion is destroyed. An easily decantible sediment is then ob-

tained in addition to a clear water and oil phase. In contrast with "real" sour cream butter, this sedi-

ment content is significantly lower. One reason is that the fat-free dry matter (part of which consists of

protein) is less in the case of sweet cream butter than is the case with sour cream butter.

Acid is added, and the product is heated to a temperature of 70 - 75°C; an adequate reaction time is

then allowed.

The oil is then concentrated in the oil concentrator to approx. 99%. The oil is heated to 90 - 95° C for

instance in the following plate heat exchanger, and it is then concentrated to 99.5% in the oil polishing

separator. It is necessary to add wash water upstream of the separator so that residual salt particles in

solution can be washed out.

Care must be taken to ensure that the pH does not rise again when the wash water is added. The

wash water should thus be adjusted to a pH of 4.5 - 4.6 with acid before it is added to the product.

51

The final value of the oil of 99.8% is adjusted in the downstream vacuum evaporator. For processing

salted butter, it is extremely important to ensure that all parts of the installation which come into con-

tact with the product are made of special corrosion-proof materials.

A three-phase decanter is to be recommended as an oil concentrator because of the high decantible

sediment content.

3.3.3.4 Production of butteroil from sour cream butter

Sour cream butter is produced from biologically acidified cream. The pH value of the butter is bet-

ween 4.5 and 5.2 depending on the country of origin.

Processing of sour cream butter into butteroil is generally the least expensive method. This is however

only partly true when the pH is between 4.7 and 5.2.

Butter melting

Butter

Oil concentration

Oil polishing

Washwater

Vacuum drying

Butteroil > 99,8 %

Serum

Washwater

Figure 32: Diagram of butteroil made from sour cream butter

When sour cream butter is processed, a third liquid phase (emulsion phase) is not present, as has al-

ready been stated. The most important for the design of the plant is that the separable solids (denatu-

52

rated protein because of the low pH value) can amount to as much as 2% absolute. In general, the

value is between 1.3 and 1.5% DS.

For processing sour cream, it is particularly important to ensure that the melting process in the melting

system is gentle, as localised over-heating will relatively quickly lead to protein burning. The product

leaving the butter melting system at a temperature of 45 - 55° C is heated in the plate heat exchanger

to 70 - 75° C, and is then pumped to the three-phase decanter. The oil is concentrated in the decanter

to 97 - 99%, and is heated to 90 - 95° C; it is then brought to a concentration of 99.5% in the oil pol-

ishing separator. The residual moisture content is reduced to less than 0.1% by evaporation in the

vacuum evaporator. The serum phase generally has a fat content of less than 0.8%; accordingly, if we

consider the amount obtained (10 - 12% of the amount of raw product), fat recovery is only worth

while if daily quantities are high. The decantible solids are concentrated in the decanter to 20 - 45%

DS as required, and are then fed from the decanter discharge to the tank. The solids consist mainly of

denaturated protein. In addition, a fat in DS of 2-5% must be expected. The oil-enriched heavy phase

from the oil polisher is recycled back into the process.

It is necessary to add water upstream of the oil polishing separator in order to ensure optimum

"washing out" of the residual protein, and also at the same time to stabilise the separation zone in the

bowl of the oil polishing separator in the required position. It is good policy to adjust the pH of the

wash water beforehand.

For further utilisation, the denaturated protein discharged by the decanter can be converted into a sta-

ble soluble state. In this form, the protein itself can be used to enrich liquid milk end products.

3.3.3.5 Processing of Cream and Butter with a high FFA content

As already mentioned, when butter with high initial FFA values is processed, perfect butteroil can still

be obtained by saponification of the short-chain fatty acids, followed by separation of the resulting

flocculate.

A suitably prepared wash water (pH > 11) is added to the flow of oil upstream of the oil polishing sepa-

rator. The free fatty acids come into contact with the basic water, are saponified and are simultane-

ously washed out. The wash water with the free fatty acids is separated from the oil in the oil polishing

separator. The oil leaving the oil polisher then meets IDF standards with respect to FFA values.

Before "Wash water with caustic" is added, the oil must have a concentration of more than 99 % fat.

53

3.3.3.6 Addition of antioxidants

Antioxidants are additive substances which prevent an increase in the peroxide number of the oil, and

to some extent reduce the peroxide values already present.

The following can for instance be used:

• Tocopherol

The final concentration of tocopherol in the butteroil must be less than 200 ppm.

Westfalia Separator AG has the knowhow for preparing and adding substances of this nature.

54

4 Machines used for making butteroil

4.1 Cream concentrators

The special design features of cream concentrators are directed towards the following:

• Attainment of a high cream fat content

• Maximum separating efficiency to achieve the lowest residual fat content in the discharging heavy

phase

• Fast and precise partial solids ejection from the bowl in order to minimise fat losses.

1. Feed

2. Cream discharge

3. Skim milk discharge

4. Skim milk pump

5. Cream pump

6. Discs

7. Soft-stream inlet

8. Sediment holding space

9. Sediment ejection ports

Figure 33: Bowl cross-section of cream concentrator MSD 200-01-076

The 40% cream to be concentrated is fed through the central feed tube (1) with a certain flow velocity

into the inlet chamber (7) which rotates at the same speed as the bowl.

The energy of flow in the stationary feed tube is converted into pressure energy in the optimally wid-

ened inlet chamber (principle of the soft-stream system).

��

��

1

32

4

5

67

8

9

55

The feed to the disc set (6) is throttled, thus ensuring that there is always liquid in the lower part of the

central distributor bore. Other throttles are arranged after the first throttle in such a way that there is an

uninterrupted flow of liquid right into the disc set. Vacuum (flow interruption) and shear forces are thus

avoided. The soft-stream system guarantees optimum separation efficiency and a high level of con-

centration.

The cream is separated into skim milk and cream in the disc set.

Both components are conveyed foam-free and under pressure by means of centripetal pumps (4 and

5) to the outlets (2 and 3). The separated solids collect in the sediment holding space (8) and are pe-

riodically ejected through ports (9). The solids ejection process is initiated automatically. The cream

centripetal pump (5) and the centripetal pump for the heavy phase (4) must be precisely adjusted to

the throughput conditions of the cream concentrator.

All centrifuges in the MSD series can be used for cream concentration. The throughput capacity for

40% cream is 30 to 50% of normal milk separation capacity.

Type of machine Feed capacity l/h

MSD 50-01-076 up to 2500 l/h

MSD 90-01-076 up to 6500 l/h

MSD 170-01-076 up to 11000 l/h

MSD 250-01-076 up to 16000 l/h

The stated feed capacities are mean values and can vary depending on

the plant design.

Table 5: Feed capacities for cream concentrators

4.2 Oil concentrators / oil polishing separators

Westfalia Separator now offers two different types of separator for oil concentration. Whereas type

RSA separators were mainly used in the past, these are now increasingly being replaced by semi-

hermetic separators.

A semi-hermetic separator has been developed in response to specific customer requests and also in

order to achieve maximum concentration of the oil phase. Concentrations of between 99.6 and 99.8%

can be achieved with this separator. Particularly when AMF with a reduced FFA content is being

made, high oil concentrations during separation reduce the residual soap content in the oil.

56

1. Feed

2. Heavy phase discharge

3. Light phase discharge

4. Heavy phase pump

5. Distributor

6. Disc set



9. Sliding piston

Figure 34: Bowl cross-

section of the MSD 90-97-076

These new separators with the model designation MSD 90-97-076 and MSD 170-97-076 have a her-

metic seal in the oil feed and the oil discharge. The heavy phase is discharged via a centripetal pump.

Special design features on the disc stack and separating disc enable the emulsion phase to be dis-

charged separately.

Rapid and precise partial solids ejections minimise losses. The specially designed disc set permits

high ejection frequencies such as are required occasionally for processing butter.

��

��

3

12

4

5

6

7

8

9

57

1. Feed



4. Heavy phase pump

5. Light phase pump

6. Distributor

7. Discs



10. Sliding piston

11. Rising channels

Figure 35 : Bowl cross section of an oil separator type RSA 60-01-076

For oil concentration and oil polishing, the separating zone inside the centrifuge bowl is displaced to

the periphery of the disc set because of the high oil concentration. For this reason, the product to be

treated is guided into rising channels (11) located towards the periphery of the disc set.

A constant pressure valve is fitted in the oil discharge line (3) in order to maintain a constant separat-

ing zone. Special valve switching has been developed in order to reduce oil losses after partial solids

ejections as a result of the peripheral position of the separating zone. The necessary valves are con-

trolled by a timing unit. The product flowing into the centrifuge is separated into an oil phase and "se-

rum phase" (heavy phase) in the disc set (7). At the same time, the solids are removed and collect in

the sediment holding space (8). The oil phase flows inwards and is conveyed foam-free and under

pressure to the outlet (3) by means of the centripetal pump (5).

The heavy liquid phase flows outwards and is conveyed by centripetal pump (4) under pressure to

outlet (2).

The separated solids are instantly ejected at periodic intervals through ports (9) by movement of the

hydraulically operated sliding piston (10).

The separators listed in table 6 are available for concentrating and polishing the oil.

��

��

1

3

2

4

6

7

11

89

10

5

58

Separator type Oil concentration in kg/h Oil polishing in kg/h

MSD 50-01-076 1200 1500

RSA 40-01-076 2000 2500

RSA 60-01-076 3000 5000

RSB 100-01-776 4000 7000

RSB 150-01-776 7000 10000

RSB 200-01-776 10000 14000

MSD 90-97-076 3500 6500

MSD 170-97-076 9000 13000

The stated feed capacities can be varied slightly depending on the design of the plant.

Table 6: Feed capacities for oil concentration and oil polishing

4.3 Skimming separators

Warm milk separators available in the sales program are used for skimming; however, their disc sets

have to be modified to meet the specific application (5). Precise knowledge concerning the butteroil

process is required for designing the machine. Skimming separators have to solve different tasks in

relation to the raw product used and the system concept.

59

4.4 Three-phase decanters

The three-phase separating decanter is a horizontally arranged centrifuge with a cylindrical/conical

solid-wall bowl containing a conveyor screw.

8 7

6

25 3 4 1

1. Feed tube

2. Distributor

3. Separation space

4. Bowl

5. Conveyor screw

6. Solids discharge



Figure 36: Cross-section of the three-phase decanter type CA 450

The field of application of the three-phase decanter is the continuous separation and clarification of

liquid-liquid-solid suspensions.

For making butteroil, the decanter is used as a machine for pre-concentrating products with a high

solids content. So-called Nizo butter is processed into butteroil in Europe. Special cultures are added

to the butter during the buttermaking process. This reduces the pH value to approx. 5.2. Aroma cul-

tures are required in order to achieve a different taste. The process of adding the cultures increases

the solids content and thus increases the load on the oil concentrator during the oil separation proc-

ess, as large quantities of denaturated solids occur as a result of the low pH value.

The continuous method of operation means that decanters offer higher system capacity for processing

butter into butteroil.

60

An oil concentration of 95-98% is achieved.

The solids can be concentrated to approx. 35-40% DS .

The product to be separated flows through the centrally located feed tube (1) into the inlet chamber of

the distributor (2), and from there through channels into the separation space (3) of the bowl (4) in

which it is accelerated to bowl speed. Under the influence of the centrifugal field, the solid particles in

the clarifying zone settle outwards on the wall of the bowl.

The conveyer screw (5), which rotates at a slightly higher speed than the bowl shell, continuously de-

livers the centrifugally removed solids to the small diameter end of the bowl, where they are lifted out

of the liquid due to the conical shape of the bowl. Liquid is removed by centrifugal force when the

product passes through the drying zone. The solids are then discharged through openings at the end

of the bowl into the catch chamber of the frame, where they are seized by the vanes of a scraper ring

and ejected from the housing (6). The liquids flow between the spirals of the conveyor screw towards

the cylindrical end of the bowl. When they pass through the separating zone, they are separated into

light and heavy liquid phases. The light phase flows inwards radially to the bowl axis, while the heavy

phase moves outwards radially to the bowl wall. The two separated and clarified liquid phases dis-

charge by gravity via regulating rings and tubes (7 and 8).

The throughput capacity of the decanter depends on the separating and clarifying characteristics of

the feed product, on the concentration of solids in the product and on the maximum permissible solids

content of the clarified liquid. It can be adapted to a large extent to the conditions and requirements of

the plant.

The throughput capacity of the CA 450 is between 5000 and 10,000 l/h depending on the plant con-

cept.

61

4.5 Butter melting system BMSA 5000

Elevator

Block Cutter

Melting tank

Plate heatexchanger

Figure 37: Functional diagram of the butter melting system BMSA 5000

Butter blocks with a product temperature of up to -20° C are fed to a block cutter via the block feed

device. An adjustable block conveyor in the feed shaft ahead of the cutter drum ensures a constant

product feed into the melting tank. The rotating cutter drum cuts the butter block evenly into butter

pieces each weighing 2 - 4 g.

The cut pieces of butter fall into the enclosed melting tank. The melting tank holds approx. 1500 l

product at a temperature of 45 - 65° C. The product circulation pump conveys 2 to 4 times the quantity

in relation to the butter feed quantity through the plate heat exchanger back to the melting tank. The

product temperature achieved in the plate heat exchanger is between 65 - 85 °C. A product discharge

pump conveys the melted product to the butteroil system. The built-in agitator ensures adequate tur-

bulence in the melting tank. Any pieces of paper are retained by the sieve in the tank.

Tubular screens can be installed downstream of the pumps for safety reasons.

The melting system must be started up with product. If water is used for the start-up phase and if

product to be melted is then added, a very stable emulsion forms relatively quickly in the melting tank;

this poses problems for continuous production.

62

Performance data:

Butter capacity: 3 - 7 t/h

Butter temperature: + 10 °C to - 20 °C

Product temperatures:

a) in the buffer tank 45 - 65 °C

b) in the return-flow product: 65 - 85 °C

c) in the product stream to the butteroil system: 45 - 65 °C

Product temperatures also depend on the type of butter used.

The hourly capacity of the system can be regulated smoothly.

4.6 Vacuum unit

A vacuum unit is required for removing residual moisture from the butteroil. The permissible residual

moisture content must not exceed 0.1% according to IDF regulations. The moisture in the oil evapo-

rates at a vacuum pressure of 50 - 100 mbar.

The necessary vacuum is produced by means of a liquid-ring vacuum pump (3). A surface condenser

(4) is installed upstream of the vacuum pump in order to reduce the pump capacity. The amount of

vapour is reduced in the surface condenser by means of condensation. Fat mist, which is drawn off

from the vacuum tank with the vapour, crystallises in the vacuum pump and can be drawn off in the

downstream tank (5).

63

LSH

PI

6

1

4

3

5

2

1. Vacuum tank 4. Surface condenser2. Pressure maintaining valve 5. Tank3. Vacuum pump 6. Pump

Cooling water

toPackaging

Figure 38: Illustration of a vacuum unit

Pump (6) conveys the finished butteroil to the packaging line. Valve (2) closes if the feed is inter-

rupted, so that the vacuum in tank (1) cannot collapse.

64

5 Bibliography

1. Das große Molkerei-Lexikon M.E. Schulz

(The large dairy encyclopaedia)

2. Chemie und Physik der Milch A. Töpel

(Chemistry and physics of milk)

3. The phase inversion of high fat cream G.N. Watt

Dissertation, 1982

Massey University, New Zealand

4. Rahm- und Fettkugelschädigung, H.R. Lehmann

ein Report aus der Praxis

Deutsche Molkereizeitung

Edition 21, 22, 23 - 1988

(Cream and fat-globule damage; a report from practice)

5. Entrahmungs-Separatoren für die Molkereiwirtschaft H.R. Lehmann

Technisch-wissenschaftliche Dokumentation Nr. 7 K.H. Zettier

Westfalia Separator AG, Oelde

(Separators for the dairy industry)

6. Maschinen und Prozesse für der Butterei H.R. Lehmann

J. Kreimer

W. Hoffmann

7. Prozeßlinien für die Herstellung von Butteröl H.R.Lehmann

E. Dolle

A. Uphus

Printed: 30.Jan. 1996

65

66

A company of mg technologies groupWestfalia Separator Food Tec GmbH · Werner-Habig-Strasse 1 · D-59302 Oelde (F. R. Germany)Tel. ++49 / 2522 / 77-0 · Fax ++49 / 2522 / 77-2089, -2821 · Internet: www.westfalia-separator.comE-mail: [email protected]

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Westfalia Separator MSD 90-01-076