GEA Mechanical Equipmentengineering for a better world
Systems and Processes from
GEA Westfalia
Separator for the
Fruit-Processing and Juice-Making Industries
3
GEA Westfalia Separator
 . Introduction

 . Fruit and Vegetables as Raw Materials
 . The anatomy and physiology of fruit
and vegetables
 . Definition of raw material
 .. Fruit and vegetable juice
 . Production of Fruit and Berry Juices
 . Production of apple juice by centrifugal
separation technology and dynamic
filtration
 .. Milling apples before extracting the juice
 .. Producing “natural cloudy” apple juice
(single strength)
 .. Producing apple juice by applying
enzymes
 .. GEA Westfalia Separator frupex
®
process
for producing clear concentrate
 .. Performance data for decanter extraction
of juice from apples
 .. Yield

 . Production of grape juice
 . Plum / date and cherry as examples of
stone fruits
 .. Date juice concentrate / liquid sugar /
feed yeasts
 .. Cherry
 . Currants and strawberries as examples
of berry fruits
 . Production of purée
 . Special Applications
 . Processing residuals
 . Treating trub using decanters or separators
 . Concentrating retentate
 . Tropical Fruits
 . Pineapple
 .. Processing beverage juice
 .. Mill juice production
 . Mango
 . Banana
 .. Banana juice
 .. Banana purée
 . Pomegranate
 . Production of Vegetable Juices
 . Carrot juice
 . Producing beetroot juice
 . Producing pulp concentrate and
juices with a defined pulp fraction
 . Secondary Plant Metabolites from
Natural Raw Materials
 8. Herb Extracts / Special Juices /

Nutraceuticals
 . Systems for the Juice-Making Industry
 . Decanters
 .. GEA Westfalia Separator varipond
®
–
reliable mastery of solids concentration
 .. Drive systems
 . Clarifiers – high product quality
and yield
 .. GEA Westfalia Separator hyvol
®

and hydry
®
machines
cover the full capacity range
 .. GEA Westfalia Separator ecoplus
separators for economic production of
juice in the low capacity range
 . Rotary brush strainer and hydrocyclone
 . Ceramic membrane filtration
 . Line and control system –
better from a single source

 . Summary

 . Literature
Contents
1. Introduction

The fruit juice industry is a comparatively young
sector. Juice has only been produced on a large
industrial scale since the s, when the first
evaporator for citrus juices was developed in the
USA. As hygiene standards became stricter, the
products acquired a longer and longer shelf life –
a key condition for the continuous growth of the
manufacturing companies.
While markets in China, India and Eastern Europe
are still growing today, the Western markets of
Europe and North America are now experiencing
cutthroat competition.
In these saturated markets, niche products such
as those made from tropical fruits or so-called
superfruits, premium juices (NFC – not from
concentrate), purée, organic juices or products
focusing on secondary plant metabolites are now
becoming more and more important. If you look
around the beverage section of a supermarket
these days, you will discover a fascinating variety
of fruit and vegetable juices. Virtually no other
segment in the food industry is characterized by
such a high degree of product diversification.

A healthy diet is more of an issue than ever. This
explains the current success of superfruits such as
acai, goji berries, acerola, cowberries, cranberries
and buckthorn berries.
Juices are made from these fruits not just because
of taste, but primarily because of their nutritional

values. The high level of antioxidants, which are
ascribed a prophylactic effect against cancer, and
other diseases, promises added value which is
causing more and more consumers to reach for
these products.
These innovative products have resulted in
new demands on an industry in which high
yield has always had absolute priority. The
focus is increasingly on machines which are
easy to clean, sealed for maximum hygiene,
processing without oxygen to reduce oxidation
and particularly rapid, yet gentle juice extraction.
GEA Westfalia Separator supplies customized
processes and process lines for these and many
other challenges.
Centrifugal separation technology is still at the
heart of cost-conscious production of high quality
juice. It ensures optimum initial clarification
before filtration, with minimal loss of juice.
GEA Westfalia Separator

hydry
®
and hyvol
®

centrifuges provide the right concept for every
requirement, depending on whether high yield
or maximum throughputs are required. The
GEA Westfalia Separator frupex

®
method
shows how it is possible to combine a gentle
manufacturing process with maximum economy.
The perfect complement is membrane filtration
using ceramic elements. It has proven its worth in
the most difficult applications and its rugged filter
membranes and minimal costs are convincing.
As the solids are concentrated to the maximum,
product losses are extremely slight. Retentates no
longer require follow-up treatment. This modern
filtering technique has a very wide variety of
applications – with colored juices, too – and
is successful wherever centrifugal separation
technology reaches its natural boundaries. Further
potential applications include peeling water
clarification and processing of excess product
from the canning industry or from the fresh fruit
and vegetable trade.
1
2
6
7
8
9
11
12
10
14
13

Fig. 2 Section
through the grape
5
3
4
4
6
GEA Westfalia Separator
2. Fruit and Vegetables as Raw Materials
2.1 The anatomy and physiology of
fruit and vegetables
Processing of the following natural products is
outlined below:
• Pomes (apples, pears, quinces, etc.)
• Stone fruit (cherries, plums, peaches, apricots,
etc.)
• Berries (currants, gooseberries, strawberries,
raspberries, blackberries, bilberries, etc.)
• Grapes
• Tropical fruits (pineapple, mango, banana,
pomegranate, etc.)
• Vegetables (carrots, beetroot, radish,
horseradish, celery, etc.)
• Plant extracts
Fig.  shows a section through a grape. Three
clearly distinct areas of tissue can be made out:
• Exocarp (skin)
• Mesocarp (flesh)
• And the area for seeds or pips
The skin of the berry has a primarily protective

function and usually contains only limited
fractions of valuable juice. In red grapes, this
area contains the tannins and anthocyanins.
The latter are enclosed in sac-like dye containers
enclosed in membranes within the cells. The
cells in turn are very small and have a stable cell
wall. There are almost no intercellular spaces.
Although the properties and composition of the
raw material and of the products made from this
vary considerably, the anatomy and physiology
of these edible higher plants are similar. The
fundamental relationships between them will be
illustrated using the examples of the grape and
the apple.
The mesocarp, which dominates in terms of
quantity, contains a great many large cells (up to
a thousand times larger than the skin cells) which
contain almost all the characteristic and desired
constituents. The liquid in the vacuoles of fruit
and vegetables contains sugar, acids and salts in
solution. The walls of the cells of fruit flesh are
very thin, some of them even collapsing during
the ripening process.
This creates intercellular spaces which, in addition
to the liquid, also contain relatively large quantities
of air. Even slight mechanical manipulations are
usually sufficient to destroy these cells.
The third important area contains the seeds
or pips. These are often very hard and usually
contain large quantities of tannins, so damage to

them should be avoided during processing.
The fine structure of this cellular tissue can be
seen in Fig.  in the example of an apple. Its
structure means that each cell has 14 adjacent cells
from which it is separated by a central lamella
consisting largely of pure polygalacturonic acid
(pectin).
The primary wall responsible for stability and
elasticity is attached to the central lamella.
Seed
 Endosperm
 Coat
 Embryo
Structure of the grape:
Pericarp
 Exocarp (skin)
 Locule
 Septum
 Mesocarp (flesh)
 Cuticle
 Peripheral vascular bundle
Vascular bundles
 Ovular
 Central
 Peripheral network
 Start of stem
 Brush
Microfibrils made of cellulose for wall stability are
embedded in pectins, proteins and hemicelluloses
of very different structures. These hydrocolloids

form the basic amorphous structure which
facilitates the metabolic processes of the cell.
If fruit contains a lot of pectin (currants, for
example, but also certain types of grape), this
has a great deal of water bound in it and this
makes it more difficult to obtain liquid from
the vacuoles. To obtain juice economically, it is
normally beneficial to break the pectin down
using enzymes.
To extract the juice from fruit and vegetables, the
cell walls have to be broken open at a minimum
of one point. In practice, this is usually achieved
by a combination of mechanical and enzymatic
measures, supported by high temperatures with
certain products. Heating mashes makes the
cell membranes permeable to juice. Some of the
pectins are hydrolyzed by heat in this process.
In process technology terms, the actual juice
extraction which follows destruction of the cells
is a separation of solid and liquid into serum
and pulp or juice and pomace. If the phases are
separated in presses, the active principle is the
difference in pressure. The juice finds a way out
through the insoluble constituents of the mash.
With decanters, the active principle of separation
is centrifugal force, which separates the liquid and
solids on the basis of their differing densities.
Depending on how the fruit has been pretreated and
the phase separation technique, the juice obtained
contains a certain quantity of trub substances.

The particle size of these trub substances ranges
from the colloidal to the coarsely-dispersed, in
other words from less than a micron to several
millimeters. The particles are essentially made
up of fragments of cell wall, mainly skin, and
accordingly contain high quantities of pectin,
cellulose, minerals, proteins, lipids and tannins.
As in natural cloudy apple juice, they can also
include reaction products that originate from the
cell compartmentalization being broken up in the
milling stage. Some or all of these particles are
removed as processing continues.
2.2 Definition of raw material
2.2.1 Fruit and vegetable juice
Only healthy, unfermented fruit/vegetables
suitable for consumption and sufficiently ripe
may be used to make fruit and vegetable juices
and products (semi-finished products) derived
from them. In addition to raw fresh produce,
it is also possible to use products which have
been chilled to extend their lives. However, no
constituents essential for the production of juices
may be removed.
Certain codes (AIJN Code of Practice) are used to
characterize the individual products in Europe.
These codes are available for the following, for
example:
• Apple and pear juice (pome fruit)
• Apricot and sour cherry juice (stone fruit)
• Blackcurrant and raspberry juice (berry fruit)

• Orange, grapefruit and lemon juice (citrus
fruit)
• Pineapple and mango juice (tropical fruit)
Vegetable juices can be made from:
• Root vegetables (carrots, beetroot, radish,
horseradish, celery, etc.)
• Perennial vegetables (rhubarb, asparagus)
• Tuberous vegetables (potatoes)
• Leaf and flowering vegetables (spinach,
cauliflower)
• Fruits (tomatoes, bell peppers, cucumbers,
pumpkins)
• Leguminous vegetables (peas)
In terms of quantity, carrot and tomato juice
dominate. In the production of juices from
medicinal plants, comparable production
processes are frequently employed, which is why
valerian and nettle should be included here. For
the sake of completeness, it should be mentioned
that beverages can also be made from cereal
mashes treated in different ways.
7
GEA Westfalia Separator
Fig 3 Anatomy of apple tissue
a: Cross-section; b: Electron microscope image,
freeze-dried material; c: Peel; p: Flesh
100 µm100 µm
aa
p
p

b
10 µm10 µm
c
c
8
GEA Westfalia Separator
3.1 Production of apple juice by
centrifugal separation technology
and dynamic filtration
Fig.  shows applications for centrifugal
separation technology in the different processing
stages from the apple to the end product. Clear
concentrate dominates in terms of quantity, but
the production of “natural cloudy” juices with
and without concentration (single strength)
has become more and more established in
recent years.
Decanters have been used for some years now to
extract the juice from the fruit and to concentrate
the trub or retentate. Polishing following juice
extraction/fining is the responsibility of self-
cleaning separators. Ultrafiltration using ceramic
membranes gives the juice the required clarity.
3. Production of Fruit and Berry Juices
Fig. 5 Eccentric screw pump with force-feed
and connected macerator
3.1.1 Milling apples before extracting
the juice
The first important process technology step
in the production of apple juice is to mill the

apples. Particle sizes from    mm diameter are
the objective for presses,    mm for decanter
use. The mechanical destruction of the cell tissue
eliminates its compartmentalization and combines
the enzymes inherent in the fruit with the liquid
in the vacuoles. Uncontrolled oxidation processes
and pectin degradation occur immediately, as do
trub-forming reactions.
The following properties are required of a system
to mill whole apples:
• Sealed system which does not increase
the quantity of air naturally present in the
intercellular spaces. This significantly reduces
foaming and consumption of ascorbic acid.
• Narrow range of particle sizes as a function
of ripeness. If the pieces of apple are too big,
this will result in a lower yield; if they are too
small, they will increase the colloid content
of the juice and make phase separation
more difficult.
The fast-running grinding or hammer mills which
are usually used only satisfy these requirements to a
certain extent. Fig.  shows a system designed
specifically for the requirements outlined
above. An eccentric screw pump which is
force-fed by a filled raw material hopper
upstream ensures that the apples are initially
milled and then feeds a macerator in the
immediate vicinity within the sealed system; the
macerator has an interchangeable hole plate and

cutting head.
The number of cutting plates in the macerator
varies. This allows individual adjustments to be
made to suit the state of the fruit. Ripe apples
need to be coarsely cut; underripe apples need a
more intensive milling process.
The hopper above the eccentric screw pump
maintains throughput at a constant level. If
necessary, it is fed via a metal detector and it
controls its filling level by means of min. / max.
sensors. A mash buffer tank is consequently not
required on the short route to phase separation.
Following milling, further treatment of the mash
depends on operational objectives. The variants
below are found in the field:
• Direct juice extraction without mash stacking
or storage, usually to produce single-strength
juices
• Addition of enzymes to the mash in the cold
state
• Addition of enzymes to the mash at
heightened temperature (approx.  ˚C)
• Total liquefaction
In practice, these options are combined with the
addition of ascorbic acid to prevent browning.
10
GEA Westfalia Separator
3.1.2 Producing “natural cloudy” apple
juice (single strength)
“Natural cloudy” apple juice is becoming more

and more popular due to its image as a natural,
healthy product.  to  percent of all apple
juice in Germany is consumed in the “natural
cloudy” state.
The consumer expects the trub in “natural cloudy”
juices to remain evenly distributed, in other
words, not to settle. Several physical variables
are responsible for the suspension stability of the
substances which create turbidity:
• Particle size
• Particle density
• Serum viscosity
• Particle shape
• Particle charge
Fig.  compares the particle size distributions of
juices extracted by decanter and by press. In
decanter juice,  percent of the particles are
smaller than µm, whereas in press juice, this
figure is only  percent.
The key factor in the production of “natural
cloudy” juices is rapid processing. Pasteurization
must follow immediately after extraction of juice
to inactivate the natural enzymes in apple.
Fig.  shows the change in particle sizes due to
the effect of an added pectolytic enzyme. Damage
to the hydrocolloid sheath of the particles causes
the particles to agglomerate. This results in
clarification of the juice. A similar reaction is
caused by the fruit’s own enzymes contained in
the juice when it is left to stand.

To produce a juice high in trub content, a regular
milling step can be followed by an ultrafine
milling step. A variety of systems is in use, the
following results were obtained in the field with
a GCE  with Westfalia Separator
®
varipond
®

in combination with a toothed colloid mill.
10
9
8
7
6
5
4
3
2
1
0
0.1 1 10 100
Particle size [ µm ]
Percent proportion by volume related to
the total volume of all particles
11
GEA Westfalia Separator
16
14
12

10
8
6
4
2
0
0.05
0.35
1.23
4.3
15.04
0.15
0.53
1.86
6.52
22.84
0.23
0.81
2.83
9.91
34.69
52.68
20
50
120
0
Particle size [ µm ]
Time [ min. ]
Percent of total volume of all particles
Fig. 7 Trub breakdown with pectolytic enzyme preparation

The whole of the sealed process, from milling the
apples to the trub-intensive apple juice, ideally
takes only a few minutes. Investigations at
Wädenswil College in Switzerland showed that
the apple flavor starts developing immediately
after milling. The flavor initially becomes more
intense until the desired fresh apple note is lost
after a while.
It was not possible to match this reaction / subjective
perception to a specific chemical compound. The
result recorded was that the most intensive and
best flavor is achieved about ten minutes after
the apple has been milled. These processes should
then be inhibited by thermal pasteurization.
The proportion of stable turbidity is higher than
with conventional pressing technology. Viscosity,
on the other hand, is in the usual range between
. and  cStokes.
If a particularly high-viscosity juice with values of
over  cStokes is to be produced, it is necessary to
heat the mash to    ˚C. Light-colored juices
with stable and not overly intensive turbidity
require ascorbic acid be added to the mash before
centrifugation. At no time can the mash stand
and come in contact with air. Under certain
circumstances, a protective gas blanket can be
used over the process line.
Prognosis for stable juice turbidity in the bottle
It is possible to predict the subsequent turbidity
of the juice using a simple prognosis test.

Changes in comparison to the level of turbidity
directly after juicing are due to sedimentation of
coarse particles and changes in structure during
subsequent development.
Turbidity stability is measured by a centrifugation
test. Turbidity stability (percent T) is given in the
form of the turbidity of the supernatant following
centrifugation (T
z
) as a percentage related to the
turbidity of the juice before centrifugation (T
o
).
This test is based on the match between the
turbidity in the supernatant of the centrifuged
juice and the turbidity in a juice which has been
stored in a bottle for a year.
The following holds true:
T
0
= turbidity measured in turbidity units (TE / F)
in the shaken sample of juice.
T

= turbidity in the supernatant following
centrifugation ( min. at  g in TE / F).
% T = turbidity stability = proportion of turbidity
in the supernatant related to the original turbidity
in the shaken sample of juice.
Fig.  shows the turbidity and turbidity stability

of two apple juices, comparing production by
press and decanter.
12
GEA Westfalia Separator
Fig. 9 Toothed colloid mill
Fig. 10 Turbidity and turbidity stability of two apple juices,
comparing production by press and decanter
These data show that with both techniques, around
half the original turbidity will remain stable in
suspension, but the decanter juice has three times
greater turbidity intensity compared to press juice.
3.1.3 Producing apple juice by adding
enzymes to the mash
Technical enzyme preparations have been an
important constituent of fruit juice manufacture
since the s. They were initially used to
clarify and depectinize juices and then in
the early s, for adding enzymes to apple
mash. The pectolytic enzymes usually used
have polygalacturonase as their primary
activity and pectin esterase as their secondary
activity.
In addition, they may contain amylase, cellulase
and protease activities. Pectolytic mash enzymes
primarily hydrolyze the somewhat less esterified
pectins of the central lamella.
Addition of enzymes to the mash speeds up
juice extraction and increases yields. Ripe and
usually very soft apples, in particular, are virtually
impossible to press and juice economically

without the addition of enzymes.
Apple mash to which enzymes have been added
is particularly easy to juice using a decanter. The
reduction in viscosity achieved by the action of the
enzymes together with the elevated temperature
lead to higher outputs and better degrees of
clarification in the production of juices. The
-stage process combines high yields with good
juice quality, though it is virtually impossible to
produce cloudy juices when enzymes are added
to the mash.
The technical equipment required to produce
juice by adding enzymes to the mash consists of
an apple mill, mash temperature control device,
enzyme-dispensing station and a dwell tank for the
enzymatic reactions. Subsequent phase separation
with the decanter enables yields of  percent and
over to be achieved. A finisher separates off bits of
peel, pips and core, allowing the throughput of the
processing line to be increased. The parameters
which affect yield and quality are the activities of
the enzymes used, dwell time and temperature.
The combined use of pectinases and cellulases
finally leads to liquefaction of the mash.
Complete hydrolysis of sugar-containing
macromolecules causes the sugar content
of the juice to rise considerably, along with
the yield. The mash liquefaction process is legally
permitted only in certain countries.
13

GEA Westfalia Separator
Fig. 11 Decanter output in apple juice production (total liquefaction)
3.1.4 GEA Westfalia Separator frupex
®

process for making clear concentrate
Clear apple juice is usually produced by rediluting
concentrate. To this end, apple juice is produced
and then evaporated to the desired Brix content
of  to ˚Brix following fining and filtration.
In the GEA Westfalia Separator frupex
®
process
(see page ), the apple mash is juiced in
-stages using decanters. The first decanter stage
corresponds to the production of “natural cloudy”
juices. Rapid processing (with or without the use
of enzymes) creates a premium juice of uniformly
high quality.
The pomace with much of its moisture removed
is diluted with vapor condensate from the
evaporator immediately. It is discharged from
decanter I and is heated to a temperature of
about  – ˚C. Following a reaction period,
phase separation is carried out again in decanter
II. Adding enzymes during the reaction period
increases yield and throughput. The second juice
does not have the quality of the primary juice
and is not usually suitable for the production
of cloudy juices. Ideally, it is processed into

clear concentrate.
Fig.  shows a GEA Westfalia Separator frupex
®

line with reaction tanks for degradation of pectin
by enzymes. The downstream separator is for
follow-up clarification. In the initial evaporation
stages, the flavor is removed from the juice
obtained in this way, and evaporation is continued
to create a semiconcentrate of approx ˚Brix.
The semiconcentrate from which the flavor has
been removed has to be stabilized to prevent
subsequent turbidity due to reactions between
phenolic compounds and proteins. Fining agents
(such as bentonite, gelatine and Kieselsol) and /or
enzymes are usually used for this. Precise trials
need to be conducted beforehand to achieve the
best possible effect. Decanter juices have to be
treated differently than pressed juices because of
the different type of structure and concentration
of colloidal and coarsely dispersed trub
substances. Over the past few years, ultrafiltration
has become established as the method for
polishing the stable supernatant produced
during fining. Use of the ceramic membrane has
a range of benefits here, particularly the option of
concentrating the retentate to a solids content of
up to  percent by volume.
Fig. 12 GEA Westfalia Separator frupex
®

line
Raw material in
2-stage
milling station
Initial addition of
enzymes
Addition of enzymes
Hot
water /
enzymes
1
st
stage
decanter
2
nd
stage
decanter
Initial evaporation /
flavor recovery
Clarifier
Reaction tanks
Cross-Flow Filtration
Evaporator
Concentrate tank
Other advantages include mechanical stability to
pressures of up to  bar and temperatures of
over ˚C. The many advantages of this system,
in addition to its technology and engineering, are
described separately in Section ..

Finally the semiconcentrate is adjusted to the
desired Brix content in the evaporator. Fig. 
shows concepts for GEA Westfalia Separator
frupex
®
lines with the different machine types for
different processing outputs. Different outputs are
possible with different machine configurations.
The outputs quoted are based on yields of 
percent or more for mashes to which enzymes
have been added.
Fig. 13 Example concepts for GEA Westfalia
Separator frupex
®
lines
14
GEA Westfalia Separator
3.1.5 Performance data for decanter
extraction of juice from apples
Fig.  summarizes the performance data for
decanter extraction of juice from apples. In
addition to the mechanical parameters, the degree
of ripeness and temperature of the apples and the
addition of enzymes play key roles. The values
relate to use in the first stage of the GEA Westfalia
Separator frupex
®
process. Output is about 
percent lower in the second stage.
3.1.6 Yield

Since raw material is often expensive, the juice
must be obtained economically and at a high
quality.
The easiest way to represent the yield from
extraction of juice from apples is to figure how
many kg of juice have been obtained from 
kg of mash.
Yields of  percent or more can be achieved in the
-stage GEA Westfalia Separator frupex
®
process.
However, in order to get a rapid overview of yield,
it is possible to determine the dry substance in
the pomace discharged. These values can be
determined by using an infrared drying lamp
within    minutes.
3.2 Production of grape juice
In principle, all varieties which have a relatively
high acid content and produce aromatic juices are
ideal for grape juice preparation. Grapes should
be healthy and ripe and have an appropriate
must weight.
For production, the grapes should initially have
their stalks removed by a stalking machine.
Beyond this, no further pretreatment of the
grapes, such as additional pressing with rollers,
for example, is required for juice extraction by
means of decanters.
Adding enzymes to the mash of white grapes
before phase separation can increase the yield

and improve the degree of clarity of the juice
produced. The juice then has the flavor removed,
is subjected to an initial concentration process
and the semiconcentrate is fined and clarified
by ultrafiltration.
To prevent subsequent precipitation of
cream of tartrate, the contact method
is used in conjunction with the GEA
Westfalia Separator separation process.
Following this tartrate stabilization process, the
preconcentrated grape juice can be evaporated to
the desired Brix content.
The process for the production of red grape
juice is modified to extract the valuable phenolic
compounds, namely colors and tannins, from
the cells of the skins. For this purpose, with
red grapes, for example, the mash is heated to
   ˚C for    minutes and is then fed directly
to the decanter without any time to stand. The hot
juice is then vigorously exchanged with cold mash
on the countercurrent principle and cooled down
by a further cooling unit.
In the case of particularly pectin-rich varieties such
as the Concord grape, for example (Hot Concord
process), it is recommended that enzymes be
added to the mash following heating and cooling
but before it is passed to the decanter.
The following applications may arise for separators
and decanters in conjunction with ultrafiltration
during the production of grape juice:

• Extracting juice from the grape mash
• Clarifying the freshly obtained juice
• Polishing the juice clarified and stabilized by
means of enzymes or by fining agents
• Clarifying the retentate in conjunction
with ultrafiltration
• Ultrafiltration
• Cream of tartrate separation
15
GEA Westfalia Separator
16
GEA Westfalia Separator
The production of grape juice by decanter has
both qualitative and economic benefits compared
to the conventional process:
• Gentle method
• Better sensory quality
• No filtration auxiliaries required
For red grapes, there are additional benefits:
• Higher color yield
• Continuous process
• Simple cleaning
• Flexible and reliable
• Simple and space-saving
3.3 Plum / date and cherry as examples
of stone fruits
3.3.1 Date juice concentrate /
liquid sugar / feed yeasts
The growing requirement for foods means
that raw agricultural materials which were

once used only little or only locally are being
processed into usable, high-quality products.
The special decomposition method and
centrifugal separation mean that it is not only
possible to obtain juice, but also by-products for
food and animal feed or primary materials for
biotechnology and chemistry.
Fig. 15 Processing dates / plums into juice
Heating
Steam
Heating tanks
Feed belt
ClarifierEvaporator
Cross-Flow Filtration
2
nd
stage
decanter
1
st
stage
decanter
Stone removal
17
GEA Westfalia Separator
Making date syrup
During the production of date juice, the cooked
mash is juiced by decanters in two stages, the
first separation stage being to obtain direct
juice. In the second extraction stage, the sugar is

recovered once the separated date pomace from
the first stage has been remashed. This recovered
juice, with a reduced Brix content, is returned
to the diffusion stage as cooked juice. The date
pomace with the sugar removed can be broken
down further if required or used as animal feed.
The description of the process for processing dried
plums is similar to the application just described.
Description of line
Dates are cleaned intensively in a washing device
and fed via an inspection belt to either a tank
heater with stirrer or to a continuous steaming
screw. The stones are removed from the heated
dates which are then routed to the continuous
diffusion process. To this end, a partial-flow of
cooked date juice (second extraction stage for
sugar recovery) and fresh water (can be water
vapor) is added to the diffusion volume in a
particular ratio. After the required reaction time,
the hot date mash is passed to the first decanter
process stage for juicing and phase separation.
After being returned to the mash via agitator
tanks and heated for follow-up extraction (cooked
juice), the juiced solid phase passes through the
second decanter stage.
The extracted raw juice of the first stage (approx.
  ˚Brix) is routed via a buffer tank straight
to the downstream clarifier for the juice-polishing
stage. The subsequently clarified raw juice is taken
to the evaporator for concentration via a Cross-

Flow Filtration system. The concentrate (approx.
˚Brix) is processed further by the mixing unit
and the tube heater downstream for sterile filling
or tank storage.
Other applications for date processing include:
• Addition of yeast to raw juices to create
baking and feed yeasts
• Production of liquid sugar
• Production of vitamins by fermenting sugar –
Pharmaceutical products
• Production of alcohol or vinegar
Process for making dried plums into juice
The fruit is heated, the stones are removed,
pectolytic enzymes are added, the mixture
is cooked for the required reaction time and
separated into juice and pomace in the decanter
when still hot. To increase yield, the pomace
can be rediluted and extracted again in the
second decanter.
The cooked juice with a reduced Brix
content obtained in this way is returned
to the first diffusion stage. The decanter
to be used for these extraction processes
is equipped with GEA Westfalia Separator
varipond
®
as standard.
Process for making fresh plums into juice
The decanter can likewise be used to produce
juices from fresh plums. Following milling and

removal of stones, the fruit is juiced directly. A
high-performance separator then polishes the
juice to filling quality. The decanter used in the
extraction process should likewise be equipped
with GEA Westfalia Separator varipond
®

as standard.
3.3.2 Cherry
To make cherry juice, the washed fruits can be
processed in different ways. Stone removers /
finishers can be used first to prevent a blockage in
the tubular heat exchanger downstream. Heating
is performed either by tubular heat exchangers or
by steam screw (blancher).
When juice is extracted by a decanter, it is not
absolutely essential to remove stones, but the
supply tank which feeds the decanter should be
equipped with a stirrer to prevent sedimentation
of the stones and to ensure a homogeneous feed.
No tannins or cyanogens are extracted in the
decanter itself.
The flavor is then removed from the juice obtained,
it is initially concentrated and enzymes are added.
The fining process which follows addition
of the enzymes is responsible for color
stability and intensity and trub quantity. An
ultrafiltration unit with ceramic filter elements
is now used for polishing. The juices filtered
with these membranes show that color loss

can be virtually ruled out – in contrast to
polymer membranes.
Following polishing, the next step is the
evaporation process to the desired Brix content.
In addition to the two types of stone fruit already
mentioned, peaches, apricots, sloes or Cornelian
cherries can also be juiced with equal success.
The necessary process technology should be
modified accordingly.
Fig. 16 Process
for making
cherries into
juice
Raw material in
Finisher
Heat exchanger
Cross-Flow Filtration
Evaporator
Initial evaporation /
flavor recovery
Tank for concentrate
Decanter
Milling
Addition of enzymes / fining
Tanks for addition of enzymes
19
GEA Westfalia Separator
3.4 Currants and strawberries as
examples of berry fruits
The main berry fruits are currants, gooseberries,

strawberries, raspberries, blackberries, blueberries,
cranberries, bog cranberries, buckthorn berries,
elderberries and barberries. All these types of
fruit can be juiced with a decanter and clarified
by ultrafiltration.
As a representative for the general principle of
processing berries, we will explain the process
technology and achievable outputs using the
example of blackcurrants.
Fig.  shows the processing of blackcurrants into
juice. The fresh or thawed berries are taken off the
stalks, milled, heated and have enzymes added.
This product then passes through a controllable,
gentle Mohno pump to the decanter, where the
mixture is separated into juice and pomace.
Further processing of the juice to obtain flavor,
followed by fining, filtration and evaporation is
in line with the GEA Westfalia Separator frupex
®

process.
However, the machine parameters and fining
sequence need to be adapted to the particular type
of berry.
Ultrafiltration is increasingly being performed
with the aid of a Cross-Flow unit, displacing the
traditional DE filtration. It is important here to
select the correct pore size. The ceramic membrane
with a very fine pore size has become established
in practice.

The key benefit of the ceramic membrane is its
ability to concentrate the solids in the retentate
to up to  percent. This minimizes juice losses
and renders awkward diafiltration unnecessary.
Compared to plastic membranes, discoloration is
reduced as well. This saves time and money for the
subsequent evaporation step. Further comments
about filtration with ceramic membranes are
summarized in Section ..
Fig. 17
Process for
making
blackcurrant
juice
Raw material in 2-stage milling Heat exchanger
Initial addition of enzymes
Decanter
Cross-Flow Filtration
Evaporator
Tank for concentrate
Initial evaporation / flavor
recovery
Addition of enzymes / fining
20
GEA Westfalia Separator
Decanter type GCE  is fitted with GEA Westfalia
Separator varipond
®
. Outputs in line with Fig. 
can be achieved with this setup.

3.5 Production of purée
In many cases, fruit is to be made not only into
juice, but also into purée or concentrated purée.
This semifinished product serves as a starting
material for the production of products containing
real fruit, such as smoothies and baby food. The
job of separation technology is to separate off
undesired particles such as pips, skins, stalk
residues and coarse tissue from the core area. The
milled flesh is intended to be evenly distributed
in the juice.
This task can likewise be performed with the
decanter. The focus here is not on maximum
clarification, but on classification. By selecting
suitable machine parameters, the undesired
constituents of the fruit can be selectively
discharged at a high level of dry substance.
Alternatively, a purée can be made with a finisher,
though there is almost no possibility in this case
of adjusting the consistency of the purée. If you
combine a finisher and a decanter, purées of any
specification can be produced. Concentrated
purées with a solid consistency are just as possible
as a more juice-like, liquid purée. The processing
line can then also be used to make juice.
Abb. 19 Production diagram for making juice and purées from apricots
Fruit
Finisher
Initial milling pump
KZE

Decanter
Sterile filling
21
GEA Westfalia Separator
4.1 Processing residuals
In addition to the production of juices, a whole
series of other products such as fruit cocktails are
also obtained from fruit. The canning industry
- factories processing pineapple or carrots, for
example - produces peeling waste and tops and
tails. Like second-quality produce (non-standard
growth), these constituents cannot be processed
by the factories directly. Yet these parts of the fruit
contain considerable recoverable quantities of
sugar and extract and are therefore juiced like the
fruit itself. Preparation of the mash is generally
modified and adapted to suit the requirements
in question.
Fig.  shows the processing output of pear
residues. The use of decanter technology allows
parts which used to be discarded to be processed
for further extraction.
4. Special Applications
4.2 Treating trub using decanters
or separators
Trub forms in a number of process steps in
fruit or vegetable processing and this has to
be separated off and concentrated as far as
possible in subsequent steps. Examples of this
are coarse trub (which settles very quickly in

fresh, conventionally pressed juice), fining trub
and retentate from the cross-flow facility. Yeast
sediment also forms during the production
of cider.
The following strategies can be employed to
reduce the burden on fruit juice manufacturers
of having to process the trub:
• Minimize the trub fraction
• Optimize trub processing
Minimizing the trub fraction
A fundamental approach to solving this issue is
to reduce the quantity of trub produced during
juicing. Different process technology methods for
extracting juice are available, with the lowest trub
level coming from the use of centrifugal separation
technology in a decanter. The solids content can
be reduced to a minimum and concentrated in a
separator to clarify the juice.
Optimizing trub processing
Sixty to eighty percent of this trub sediment
consists of recoverable juice. Phase separation can
be performed continuously by decanter without
auxiliaries and in a sealed system. The option
of processing very quickly maintains the juice
at optimum quality. Eighty-five to ninety-eight
percent of the solids are separated off,
guaranteeing that the juice returns directly
to the main flow. The solids themselves can
be dumped.
It is important that the trub which forms is

processed fresh and has not started to ferment.
If the trub has started to ferment, this can
considerably reduce the clarifying performance
of the decanter as a result of the carbon dioxide
which forms (trub floats).
Decanter type GCE 535
4.3 Concentrating retentate
Retentate is a by-product of cross-flow filtration
and essentially consists of retained trub particles,
which were unable to penetrate the membrane,
and valuable fruit juice. The characteristics of the
retentate (a high COD value, for example) often
result in correspondingly high disposal costs.
A higher concentration of solids in the retentate
leads to a lower overall volume of retentate. There
are system-related differences between polymer
and ceramic membranes here, ceramic allowing
a greater degree of concentration.
. Secondary current separation of the retentate
circuit by separator
Depending on the system, the circulating
performance of the retentate circuit is  to 
times greater than the flux rate (permeate flow).
The retentate becomes increasingly enriched with
solids and, from a certain concentration factor,
requires further processing in batches to recover
the valuable juice.
Cleaning cycles are determined by the formation
of a layer coating the membranes. If a separator
is used in the secondary current to the retentate

circuit, cleaning intervals and permeate output can
be considerably improved. At a secondary current
output of    percent of the circulation output
of the retentate, solids are continuously separated
and too great a concentration is prevented.
A similar effect can be achieved if the separator
is installed in the feed to the operating tank of
the ultrafiltration unit and initial clarification is
carried out on the whole of the juice batch.
In this case, the separator output has to be adapted
to the permeate output. With secondary current
separation in the retentate circuit, the centrifuge
can be smaller.

22
GEA Westfalia Separator
Fig. 21 Retentate treatment using a decanter
Retentate tank approx.
50 – 60 % (by vol.)
Juice < 0.5 %
(by vol.)
Decanter
Solids 25 – 30 % D.S.
Dilution with water
to 25 – 30 % (by vol.)
Heating 80 – 85 ˚C
The solids from the centrifuge can be disposed of
with the pomace, so do not form a separate waste
flow. However, retentate is still produced in the
filter, even if in considerably smaller quantities.

As an alternative to the separator, the
decanter can also be used. It is more tolerant
of abrasive media such as bentonite and is
also suitable for elevated trub content in
the juice.
. Concentrating the retentate in batches
using a decanter
A further option for processing retentate is to
collect it in a separate tank at the end of filtration
and to clarify it in parallel with regular daily tasks.
The retentate is diluted with water, then heated
to   ˚C and clarified in the decanter. The
clarified juice then has a residual solids content
of approx. . percent by vol. and can be routed
back into current production. The hard solids can
likewise be disposed of with the pomace again.
The dry substance of the solids is in the range of
up to  percent D.S.
As a result of this process running in parallel with
the regular juicing operation, the hourly rate of
this line can be relatively small and investment
consequently low.
23
GEA Westfalia Separator
24
GEA Westfalia Separator
5.1 Pineapple
Both decanters and separators are used to process
pineapples into juice. In principle, two different
products are obtained – so-called “mill juice” (from

pineapple skin) and “beverage juice” from flesh
components. “Beverage juice” is used as juice;
“mill juice” is used purely for clear toppings in
the canning industry.
5.1.1 Processing beverage juice
After washing and sorting, the fruit arrives at
the “Ginaca” machine where it is mechanically
broken down into three components: cylindrical
flesh (the cylinders are then sliced as typically
done for canned fruit), peel and “juice material”.
This consists of the pineapple core, and the flesh
obtained from between the skin and the cylinder.
Some factories divert some of this material to
produce “crushed pineapple” – a kind of pineapple
purée. The fruit is juiced by the traditional screw
presses which generate a high proportion of solids
in the juice. Screw presses are used in a  or even
-stage arrangement.
5. Tropical Fruits
25
GEA Westfalia Separator
The discharging juice has   ˚Brix and a solids
content of up to  percent by volume. It may
contain undesired solids such as bits of peel. As
an end product, it is supposed to have a solids
content of    percent by volume for low-pulp
juice. For high-pulp juice, solids contents of  
 percent by volume are usual.
Clarification normally takes place at elevated
temperatures. There are two process technology

variants.
Initial clarification is performed by finishers
(strainers) which remove all coarse fibers. The
juice is then clarified by separators. Solids contents
in the juice produced may be set to between   
percent by volume or lower.
The juice coming from the separator can be set
to the desired solids content by controlling the
throughput.
Alternatively, the juice can also be clarified
by decanter. This makes it possible to reduce
considerably the number of process stages
required for clarification because the finishers
(strainer units) are omitted.
The juice produced in this way is evaporated to
the desired concentration in multi-stage falling
film evaporators.
A specific variant for producing high-quality
pineapple juice is to use decanters with a -gear
drive to extract juice directly from the pineapple
mash. This process is based on the GEA Westfalia
Separator frupex
®
method which uses fewer
machines. The potential savings are considerable
here, and the quality of the end product can also
be improved, as the process time at elevated
temperature is shorter and associated heat damage
and oxidation are reduced considerably.
Fig. 24 Capacity of GEA Westfalia Separator

®
hyvol
®

separators in pineapple processing