3
Preparation Plant
Preparation plant for dehydration is very similar to that used by the
canner and freezer, because up to the last stage of conservation the raw
material is prepared in similar manner, other than to provide for the
introduction of certain additives which are not common to either canned or
frozen products.
This chapter defines very briefly the type of preparation plant used in
a multi-product operation, the lay-out of which will have to be arranged to
suit the production flow of several types of vegetable (or alternatively fruit)
without too much disturbance to the original positioning of the machines,
when changing from one product to another.
The description of the various machines is accompanied by
photographs and the brief outline of their function will be amplified in later
chapters, which explain more concisely the processing details for a wide
range of fruit, vegetables and liquid products.
It is stressed that some of the preparation plant described will only be
required in a medium to large scale operation, because in a low budget
project, full automation would be neither viable nor necessary, as such a
plant may be able to be used with the simplest product cleaning facilities, a
peeler, cutter and some simple conveying equipment. Some old established
factories in Eastern Europe, specialising in onion dehydration, have operated
for years with a minimum of preparation machinery, being convinced that
hand peeling of onions, for example, produces a much better product than a
39
machine, and even their cutters have been substantially fabricated in their
own workshops. However, as indicated in Table 1 .l. (imports into the UK),
the volume produced in this type of factory is very small, and when world
prices were low in the 1970‘s many Romanian and Bulgarian factories ceased
operations in dehydration and reverted to other forms of vegetable and fruit
conservation.
It is emphasised that the preparation plant described is ‘upstream’ of
the dryer. Downstream plant is described in the chapter on selection, packing
and storage.
CUTTERS
(a) Dicers.
The dehydration process requires that produce be reduced to a fairly
small particle size, otherwise the removal of water becomes an overextended
operation, with consequent damage to the colour, texture, appearance and
general quality of the dried product. Also the rehydration ‘factor‘
deteriorates.
Dicers are cutting machines with three separate knife actions:
(1) a slicing knife positioned in the machine’s impeller, which
rotates at approximately 19Orpm, makes the first lateral slice as
the product is fed into the machine. The thickness of the slice is
adjustable but the maximum dimension is limited by the
spacing of
(2) the cross-cut knives, which are fixed to a spindle rotating at
about 1400rpm. The impeller thrusts the first cut slices on to
these cross-cut knives by centrifugal force, making strips
ranging from 7.lmm to 13mm in width, pre-determined by the
thickness of the first slicing cut.
(3) The third cut is made with a row of circular knives that can be
spaced in 3.2mm increments from 6.4 to 76mm apart. Julienne
cuts are produced using circular knives spaced 4mm, 4.8mm or
6.4mm apart.
For this type of cut, the cross-cut knife spindle is replaced
with a slice guide roll, and the slice thickness (first cut) is
adjusted to suit the circular knife spacing.
A Model G dicer can be used as a slicer to produce any thickness up to
19mm. An inner chute must be used in these circumstances to guide slices
across the slicing knife holder into the discharge chute.
The above description, and those given below, relate to one American
designed machine, noted for its high performance and reliability, and it is
used internationally.
40
There are other Continental makes, built on similar lines, and the
processor must judge which marque serves his purpose best in performance
and cost effectiveness.
The dicer is perhaps the most flexible cutter available, and will handle
quite a range of products but, with a wide product mix, other types of cutter
will doubtless be needed.
Cutter knives requk constant attention and should be sharpened
every eight hour shift, especially when used on tough vegetables, such as
carmts, swedes, turnips, cabbage, celeriac, etc. Failure to do this will give rise
to a ragged product which will matt on the drying surface, whether it be a
tray or a conveyor slat. This creates an impermeable mass which the air flow
will not penetrate, and these conditions will delay drying or, at worst, will
make even drying impossible.
Honing machines are available for both crosscut knives, circular
knives and slicing knives, and these can usually be supplied by the cutter
manufacturers.
In a medium to large operation, it is obviously wise to duplicate all
cutters, so that by having two in parallel, the knife change will not hold up
the production flow and the product can be switched immediately, without
any hold-up from one cutter to the stand-by machine. Each knife assembly
can be removed with all the knives (ie, cross-cut and circular) in situ, and
indeed can be sharpened as a unit, without dismantling each knife separately
for servicing.
This facility of course makes it possible for the smaller operator to
remove and exchange a knife assembly, so long as he carries a spare assembly,
and in this way he can avoid having to duplicate the whole machine but, of
course, there will be some delay in the actual removal of the old machinery
and replacement by the spare one, and some production time will be lost.
The shift fitter must, as a priority, watch the condition of the cutting
knives throughout his shift, very much as the seamer fitter in a cannery
watches the quality of the double seam cans passing through a high speed
can seamer at lo00 cans per minute. In both cases a lapse of attention at this
point can spell trouble. Disposable knives avoid honing costs.
Where cutters are duplicated, it is obviously wise to install two of
identical make, so that economy in carrying spare parts is achieved.
(b) J Cutter
This is eminently suitable for bulb and leafy products, such as spinach,
leeks, spring cabbage, bell peppers, parsley and other herbs, celery and citrus
fruit and the peel.
The machine operates on the principle of a high speed belt carrying
41
the product to the cutting parts. A 152mm diameter feed roll is fitted at the
feed end of the belt to the knives. This flattens the vegetable before entering
the knives and forces them into the cutting area.
By the arrangement of the circular and cross-cut knives, the J cutter
produces square cuts ranging from 6 by 6mm to 13 by 13mm, the thickness
of this square being the thickness of the original product. For example a
capsicum with flesh 4mm thick would emerge as a square flake 6 by 6 by
4mm or a larger square if the knives were adjusted. Strip cuts can be made by
removing the cross cut knives.
(c) CC Slicer
This machine will slice products up to lOOmm in diameter. Anything
larger will need a heavy duty machine, such as the Model Y slicer, or the G
dicer with the cross cut and stripping knives removed.
The standard slice for the CC slicer is 3.2mm thick but special parts are
supplied to make thicker slices, such as onions at 4mm. One benefit of the
CC slicer is that the knives are disposable, and this avoids honing and
sharpening and, in effect, these knives are cheaper than the cost of
sharpening those fitted to other machines and the cost of down-time. They
will operate for 8-12hr with normal usage and are ideal when handling
onions.
(d) OV Slicer
This is a transverse slicer for fruit and vegetables which are not more
than 70mm in diameter. Slice thickness is controlled by using a different
slicing wheel which can be selected to give a slice length (or thickness)
ranging from 1.6mm to 32mm.
The slicer will not handle sticky products but can be used for leeks,
bananas, carrots, rhubarb, celery and asparagus. The feed must be controlled
very evenly.
(e) Comitrol
This is a cutter which will produce a wide range of cuts, and will
comminute by flaking, slicing, shredding and dicing from 13mm down to
microscopic sizes. It handles equally efficiently meat, fish, vegetables and
fruit. It would have a special application in comminuting soup ingredients
down to a size suitable for instant or rapid rehydration.
(f) SC Scarifier
This is used in dehydration specifically for slitting the skin or
membrane of fresh peas. Peas are normally scarified before blanching, and
42
alp fed into the scarifier hopper from which they fall in a conhdled stream
between a rubber roller and a row of serrated wheels, revolving at a different
speed. The peas pass through in a single layer so that each pea makes contact
with the slitting wheel. The slit is made at a contmlled depth - usually about
3mm as the peas pass between the rubber roller and the knives.
The purpose of scarifying is fully amplified in the Chapter 5 on the
ptucessing of vegetables (green peas).
(g) Bean Slicer Model W
It is recommended in Chapter 5, on the subject of processing Green
Ekans, that slicing should be carried out after blanching, to avoid the loss of
bean 'seed' in the blanching water. Round pod beans are normally used for
dehydration, and the Model W slicer gives a Julienne or French-style long
cut rather than a transverse cut. The beans alp fed by a belt incorporated in
the machine to the cutting head, and kept in a straight line by oscillating
parallel guides. The head consists of a circular knife spindle, a stripper plate
assembly and a stationary knife.
The beans a= cut lengthways by the cirrular knives, removed from
between the knives by the stripper plate and guided on to a horizontal
stationary knife at high speed, causing them to be cut through the centre at
right angles to the cuts made previously by the circular knives.
A grm ban snibbing line, cluster cutters and spill proof elevator
43
Left: Urschel Model G-A dicer,
strip cutter and slicer
Right: Urschel Model J9-A
two dimensional dicer
Left: Urschel Model RA-A for
small to intermediate sized dices,
strip cuts and slices
Right: Urschel Model WVF bean slicer
4
01) Bean Snipper
This is a revolving drum with perforated slots around the periphery.
Knives are positioned to cut along the whole length of the drum, the cutting
edge being set almost up to the drum surface.
The beans tumble around as they pass through the inside of the
cylinder and, in course of travelling along its whole length, the ends project
through the slots and are cut off by the knives.
Most modem snippers are continuous in action rather than batch fed,
and any unsnipped beans at the discharge end alr? returned to the feed end
or, in the case of high capacity throughput, to a second machine in the line.
PEELERS
vegetables:
There are basically four methods of peeling potatoes and root
(1) Lye peeling;
(2) Steam peeling;
(3) Combination of heat and lye;
(4) Abrasive peeling, either batch or continuous.
The dehydrator will have to decide which method suits his
circumstances, and with due consideration to the effect of the method chosen
on the effluent problem, which can, of course, be aggravated by one or other
of these methods. Provided that the effluent problem has been taken calr? of,
and that suitable treatment has been organised, the preference will usually
lie between steam or lye peeling, and the advantages and disadvantages of
both methods can be summarised as follows:
(1) Lye Peeling
One of the main advantages is the relatively low capital cost of the
equipment, as it is quite usual for lye peelers to be fabricated from mild steel,
no particular advantage being obtained by using stainless steel. The design
is basically simple, usually consisting of a perforated metal drum, with
pockets into which the vegetables are fed, rotating in a bath of hot lye (sodium
hydroxide) solution of 5-20 percent concentration, according to the peeling
characteristics of the vegetables being handled.
Maintenance costs are low, as there are few moving parts in the
machine.
The system is capable of a wide variation in peeling technique to suit
any particular type of raw vegetable. Some processors use the thermal shock
method of high concentration and temperature, with short immersion time,
whereas others prefer a lower concentration of lye and longer dwell time. In
some cases, wetting agents are used in the lye tank, to cut down the usage of
45
sodium hydroxide, or to make more effective use of the standard
concentration being used. Another technique to economise on lye is to allow
the vegetables to pass from the peeler through a ‘retaining’ reel, which is
really a reel or rod washer with the water spray equipment removed. The
dwell time in this reel, which can be 10 - 15min, according to its capacity, has
the effect of extending the penetration effect of the lye on the skin of the
vegetable, thereby reducing the duty, and consequently the concentration of
the lye in the peeler itself. From this reel, the vegetables pass normally to the
washing process, which is either carried out in a second reel washer or in a
rotating brush washer.
On the debit side, the cost of sodium hydroxide is high, particularly
when high concentrations have to be sustained. Also a considerable volume
of water has to be used in subsequent washing, to amst caustic bum and
excessive penetration of the flesh and to remove all surface traces of lye.
Again, some further chemical treatment may be necessary if peeled
potatoes or other vegetables have to be held in a surge hopper for any length
of time prior to further processing. In these circumstances, it is usual to dose
the surge hopper with 0.5 percent citric acid to neutralise any trace of
alkalinity left by the lye treatment, and this, of course, adds to the cost of the
operation.
Where lye peeling is undertaken, very special precautions must be
taken to protect operating personnel against injury by contact with lye, and it
is essential that the staff engaged in this department are supplied with heavy
rubber boots, gloves and outer protective clothing, and goggles must be
worn at all times. Suitable warning notices relevant to the hazards must be
displayed adjacent to the peeler, and first aid equipment to deal with caustic
bums should always be close at hand.
Very rigid control of conditions of immersion time, temperature and
concentration must be exercised, otherwise heavy leaching losses will occur,
which will seriously affect the ratio and yield of end product. Leaching is the
loss, by extraction, of soluble solids in vegetables, which is caused by over-
immersion in either the lye peeling liquor or the blanching liquor. High
temperatures are also a contributory factor to leaching in some cases.
(2) Flash Steam Peeling
This method is extremely efficient, and has the advantage of creating
fewer effluent disposal problems than other methods.
The system utilising high pressure steam at 17atm ensures that even
awkwardly shaped products are evenly peeled.
Steam at the pressure indicated heats the moisture under the skin of
the vegetable in such a manner that, when pressure is reduced this moisture
46
Table 3.1 Relative peeling efficiency
FLASH STEAM PEELING SYSTEMS
TYPE 100 200 300 400 550 800 950 1250
Pressure Vessel
Volume, litres 100 200 300 400 550 800 950 1250
Door diameter, mm 200 300 300 350 350 400 400 450
Support bearings, mm 60 75 75 100 100 125 125 125
Steam connection, mm 60 75 75 100 100 125 125 125
Air connection, BSP.T.
Door seal Silicone rubber, 8mm dia. section
Speed 6 rev. per min.
Product per charge, Kg 34 67 100 134 200 226 333 666
Steam
Nominal consumptionKg/hr 100 200 300 400 600 800 1000 2000
Inlet valve, mm 25 40 40 50 50 75 75 75
Exhaust valve, mm 32 50 50 80 80 100 100 100
Electricity
25Opsi max WP (17 bar)
Air, psi 80 80 80 80 80 80 80 80
415V, 50hz, 3 phase (power), 110V, 50hz Single phase (control)
Power
Pressure vessel, KW 1.5 1.5 1.5 1.5 3 3 3 4
Feed Conveyor, KW 2.2 2.2 2.2 2.2 2.2 3 3 3
Discharge conveyor, KW 2.2 2.2 2.2 2.2 2.2 2.2 2.2 3
Performance
Typical example, Kg per hr 1000 2000 3000 4000 6000 8000 10,000 20,000
Ware potatoes
All capacities based on 30 cycles per hour
47
flashes off, lifting the skin with it.
Peeling losses can be as low as 15 to 17 percent with ware (ie, table size)
potatoes. See TABLE 3.1.
The final operation is to pass the product through a skin eliminator.
A flash steam peeler
(3) Heat-Lye Peeling
The combined use of lye and heat peeling has been developed in
America for potatoes. Tubers are first immersed in a very light lye solution,
and then pass through a gas fired infra red unit at 900°C. After the infra red
treatment, most of the softened peel is removed by studded rubber rolls in a
mechanical scrubber, and final cleaning is effected in a brush washer, which
uses a minimal amount of water.
It is claimed that caustic soda usage is cut by 80 percent and water
usage by over 90 percent, using this method. There are, relatively, no waste
water problems, as the system uses only 15-45 litres per minute against 700-
1800 litres per minute in conventional lye peeling, and the waste peel can be
consolidated to a paste of approximately 15 percent solids which, after
neutralising, can be used for animal feeding.
48
(4) Abrasive Peelers
This type of peeler has been used for many years in all branches of the
vegetable processing industry The earlier models were the ‘rumbler’ batch-
type, which cannot be considered seriously for a dehydration factory, owing
to the limited throughput and the fact that the abrasive action is too severe
and far too much weight is lost.
The new concept is to run the abrasive rollers longitudinally in a
circular cage, fitted around a centre auger. This roll cage mixes and turns the
vegetables to expose all surfaces, whilst the abrasive rolls also rotate at
adjustable speeds to control the applied abrasiveness. Thus, control is
applied on the seventy of the abrasion by instant adjustment of the roll
speed, and total exposure time is governed by the auger speed. The abrasive
rolls on these machines can be exchanged for brushes when handling thin
skinned or delicate vegetables.
It is almost inevitable that, when abrasive peelers are used for potatoes,
a considerable quantity of free starch will be released from the peeling plant,
and this again can produce an effluent disposal problem. Invariably, this
effluent has to be settled out in tanks before the waste peeler water can be
finally discharged.
It is not intended, in the foregoing summary, to denigrate or
recommend any particular peeling system, as there willbe many local factors
and circumstances to be taken into account by the dehydrator when he is
equipping his factory but the ’pros and cons’ for each system are based on
the experience of the author in several differing locations.
Tlleikpusson continuous abrasive peeler
49
Reel Washer
WASHERS
Thorough washing is essential after any of the foregoing peeling
methods, and the types of washer normally used in dehydration factories
are as follows:
(1) Slatted reel washer, rotating on trunnions, with a centre sparge
(2) Rod or wire mesh rotary washer similar in action to the reel
(3) Rotary brush washer.
pipe fitted with water spray nozzles;
washer;
Here again, the choice will depend on the degree of sophistication the
processor requires at this point in the process. Reel or rod washers are both
effective, provided efficient spray nozzles are fitted and the dwell time is
sufficient for the weight per hour being fed through the machine. Incorrectly
designed sparge pipes, with holes drilled at random along their length, to
provide the necessary water spray, can give rise to a tremendous wastage of
water, and this is a point which must receive very special attention. Some
washers have been known to consume 20 times the volume of water that
was actually required or necessary, had the proper study been applied to the
washing method.
50
The capital cost of a reel or d washer is possibly only 30 percent of
that of a modem brush washer but the latter is a particularly sophisticated
machine, which works very efficiently with most types of vegetable and,
properly controlled, will probably repay the increased capital outlay within
a season. These machines comprise a trough-shaped frame, with six or more
longitudinal rotating nylon tufted brushes, the bristles of which axe set in a
spiral fashion to assist the movement of vegetables throughout the length of
the washer. A longitudinal spray pipe, fitted with fine nozzles, is located
down the middle; it is cam-operated so that it rotates through about a",
directing the water sprays over the whole inner area of the washer, through
which the vegetables are continuously passing. The brushing action tends to
be more effective than the mere tumbling action of the simpler md washer,
as it facilitates the removal of potato eyes, and excrescences and growth
cracks in most types of mot vegetable are attacked with better effect. Water
usage on these machines is usually very economical and, given the correct
type of nozzle, a water pressure of 1.4atm is quite effective for throughputs
up to 4-8 tonnes per hour.
Reference has been made in Chapter 2 to the water usage to be
expected in a medium size plant but this figure can be wide of the mark if
proper care and attention is not given to the installation and correct operation
of the washing plant.
Hot water blancher
51
BLANCHERS
Blanching techniques and equipment are similar to those used by the
canner and freezer, and the process is carried out either by steam or hot
water.
The dehydrator may have to install both types of blancher, as certain
vegetables will respond better to steam blanching, whereas hot water
blanching is preferred in other cases.
Steam Blanchers
These can either be the rotary thermoscrew-type or a mesh conveyor
passing through a steam chest. Where additives require to be used, these
have to be sprayed on the vegetables as they leave the blancher. One school
of thought in dehydration circles believes that steam blanching inhibits
leaching losses but the latter problem has received much scientific attention
in recent years, and techniques have been developed in which blancher
liquors are buffered to reduce the tendency of soluble solids to dissipate in
the course of this process.
Hot Water Blanchers
These are invariably the rotary smw-type and are somewhat more
economical in steam usage. Additives can be intmduced directly into the
blanching liquor and control is usually more accurate than in the case of
additives sprayed after steam blanching.
An ancillary steam heated tank unit is required to make up a solution
of additives (sulphite, citric acid, sodium pyrophosphate, calcium chloride,
sucrose and saline solutions, etc, combinations of which are used with
various types of vegetable) and this solution is usually drip fed into the
blancher, or circulated by pump, and returned back to the tank, where the
required concentration is maintained at a prescribed level.
Where the level of additives xquiFed is high, it is essential to heat the
blancher entirely by closed steam coils, rather than by open steam injection,
as, by using the latter method, the condensate will dilute the liquor, create a
large volume of overflow and generally make control difficult. Open steam
injection is sometimes used as a temperature booster but should not be used
continuously.
Blanching methods vary for each type of vegetable, as will be described
later, but it is important, when selecting a blancher, to specify stainless steel
construction. With many vegetables, it is customary not to drain the
blanching liquor off for several days, and in these circumstances, stainless
steel is the most hygienic material to withstand these particular conditions.
The chemical constituents of blancher water would set up corrosion very
52
quickly in mild steel or galvanised equipment.
The desirability of retaining the blanching liquor for long periods
arises from the necessity to duce leaching losses, which have also been
refed to in the context of lye peeling. Retention of blanching liquor permits
solids leached out, at the beginning of the blanching process, to build up
fairly quickly to a level where fresh material passing thmugh no longer gives
up its solids so readily, and a liquor of relatively high density is created. By
using the buffering technique hitherto described, it has been proved
conclusively that the solids content in blanched vegetables can be in excess
of that in raw, unblanched material, and this can affect the ultimate yield of
the dry material dramatically.
An exception to this prpcedure is in the blanching of potatoes. Here
the solids are in the form of free starch, released from the cut surface of the
potato, and it is necessary that this be washed away, as it creates drying
problems by causing a condition of impermeability to arise in the bed of
material in the dryer, with serious detriment to the air flow. Also, an
accumulation of starch in the blancher sometimes sets up uncontrollable
foaming. In this case an anti-foaming agent can be used.
Blanchers should be selected only after careful consideration has been
given to their design features relating to hygiene and easy cleaning. Unlike
equipment used in canneries, which may operate on a day shift basis, the
blancher in a dehydration factory has to work continuously for some 150hr a
week, and it is absolutely essential that its construction takes this into
account, and that raw material is not left behind in augers, crevices and
inaccessible parts of the machine. The inside of the blancher should be easily
and quickly accessible for weekend cleaning and sterilisation.
CONVEYORS
The approach plant and conveying systems should all be constructed
in stainless steel, wherever contact with the prepad vegetables takes place.
Where gooseneck elevators are used, the buckets should be of plastics or
moulded rubber. Conveyor belts should be PVC-covered and manufactured
to the highest sanitary standards.
The conveying system from the blancher to the dryer should be
arranged to allow as little delay as possible in transferring blanched material
to the first stage of drying, as a high bacterial count can build up at this point,
if this precaution is not taken. This condition is aggravated where cooling
does not take place afterblanching. Where it is desirable to retain the additive
level in blanched vegetables with a minimum of loss, water cooling after
blanching is often omitted but it is essential, in these circumstances, that the
drying process starts immediately and the blanched vegetables are not left
53
Left: a spiral elevator as produced by Valley Azitornation
Right: A vertical destoner/washer
around for extended periods. This is one of the hazards in tunnel or tray
drying, where trays of vegetables have to be filled singly and loaded on to
trolleys - an operation which can take upwards of half an hour - with the
consequent delay in entering the first stage of the dryer. In these
circumstances cooling by cold water spray or cold air blast is essential but
where conveyor band dryers are used, and a rapid transfer from the blancher
to the dryer conveyor can be assured, then cooling can be dispensed with
and some thermal advantage gained in the dryer.
Conveyors used after the drying process do not require to be of
stainless construction but again care should be taken to ensure that all
equipment of this nature canbe easily cleaned as, from this point on, abrasion
of the dried product and dust will be the major problems. Vibratory
conveyors and elevators should always be used where possible with the dry
product, as these are much more hygienic and less pmne to set up product
abrasion than conveyor belts and bucket elevators. The cost of installation is
relatively high but the processor is handling an expensive product and he
cannot afford to make a lot of ‘fines’, by abrading away the finished material,
as this by-product has very little commercial value.
MISCELLANEOUS AND SPECIALISED
PREPARATION PLANT
Destoners for root vegetables: Bulk Feeders: Dry Cleaner Reels
Where root vegetables are flumed into the plant, stone traps are
invariably fitted into the outside washer, which is sunk into a concrete pit to
suit the gravity flow of water and vegetables from the flume channels. This
rugged type of washer is similar to those used in sugar beet factories.
The vegetables are elevated into the bulk feeder at the intake end of
the production line proper.
The bulk feeder, which may have a capacity of 5 - 10 tonnes, according
to the required level of throughput, has a slowly moving belt built into the
bottom of the bin and this, being set at an upward sloping angle, delivers the
produce at a measured rate on to a mss conveyor which transfers the
material to the next machine.
The bulk feeder can, of course, be fed directly by tipping farm tote
boxes or stillages by means of a mechanical box tipper, or even manually if
the containers are small. The bulk feeder is usually situated at the factory
entrance/reception area for raw material.
Where no prewashing of root vegetables has been effected by fluming,
then most root lines have a dry cleaning reel installed immediately
downstream of the bulk feeder, and this is a slatted reel rotary drum
revolving at a slow speed; this has the effect of removing clods of earth and
55
soil adhering to the roots or tubers which may have been lifted from heavy
land or in wet conditions.
Roots in such a condition may be refused by the processor as not
complying with the contractual quality specification by which the grower is
bound but, if accepted, some deduction in weight for excess soil might be
imposed, as an alternative to refusing the load.
The produce then passes to the factory-based destoner. This is
essentially a vertical screw elevator into which the vegetables are fed via the
bottom hopper, then lifted upward through a column of water, discharging
at the top, any stones or grit falling to the bottom of the machine, from where
they are removed.
Preparation Plant for Beans
A Pneumatic Separator is an aspirator specifically designed for beans
(and peas) to remove by air flow all extraneous matter, such as skin, leaf,
haulm, etc.
Cluster cutters are installed specifically when beans have been
mechanically harvested and clusters of beans are not separated entirely into
separate pods. Such a machine is not required when beans have been
manually picked.
Vibratory feed to the Snippers is essential to give a controlled flow to
however many snippers are in the line. The vibrating conveyor gives a gentle
feed which precludes the snipper drums becoming overloaded.
A bean washer is essential, especially for harvested beans and this is
usually located after the pneumatic separator.
A vibratory Feeder to the bean slicer (already described under the
heading of cutters) is necessary, again to give an even flow to the slicing
machines, so as not to over or underfeed them.
Preparation Plant for Onions
A grader is essential (a) to discard bulbs under 50mm in diameter (b)
to grade the balance in the range 50mm - 60mm and those at plus 60mm.
A dry cleaner is used to =move the loose skin and dry tops, and also
any sand or grit brought in from the fields.
A rod washer is installed with a sparge pipe and a good flow of fresh
water.
An Autocore topping and tailing machine with a Shufflo feed may be
installed - only if the onions are full globe in shape. This machine will not
handle half globe or flat onions.
This latter type of onion will have to be topped and tailed (a) manually,
or (b) by a Hydrout manually fed machine. These machines have a revolving
56
Right: Pneumatic
separator for peas and
beans
cutting/coring knife, are bench mounted with a front safety guard and have
a hole messed in the centre of the guard plate into which the onion is
placed. The revolving knife bores into the root of the onion which can then
be reversed for removal of the top. As the onion has to be held in position by
hand against the thrust of the knife, the machines can be dangerous to
operate in spite of the guarding, but everything depends on the concentration
of the operator.
The Factory Safety Inspectorate bans these machines in some countries
as being unsafe but the author has seen them used extensively in many
factories. It is a matter for the management to decide.
The alternative is to remove the core only by hand knife, and allow the
following abrasive peeler to remove all trace of the top, which an efficient
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machine will do if followed by a little hand trimming.
A continuous abrasive peeler is probably the most suitable type for
onions. These machines can be supplied with a central lubrication point for
all the revolving abrasive rollers, the augur feed and all the drives. It is
however recommended that, in factories where the mechanical engineering
staff are not always 100 percent fastidious about lubrication, a peeler where
separate grease points are fitted is a safer proposition.
A small water spray sparge pipe fitted over the elevator taking the
onion slices to the dryer is essential to remove surface sugar from the cut
onion. This sparge pipe can be fitted as a special addition to a standard
elevator.
Preparation Plant for Tomatoes and Peppers
A tomato washer is a tank with high pressure water jets and water
agitation by compressed air. The installation consists of a prewasher, fitted
with a perforated bottom, into which the produce is fed. A rotary transfer
reel or 'paddle' transfers the tomatoes to a second washer at a contmlled
speed, and they are again subjected to washing in water agitated by air jets.
The fruit is picked up at the discharge end by an upwards sloping roller
conveyor, feeding on to roller-type sorting and inspection tables. These are
elevated and the operators sit on both sides of the tables on railed platforms.
Bell peppers can also be washed and sorted by the same method but in
the case of peppers these are split by hand (machines are not 100 percent
reliable) de-seeded and washed again in a flood washer.
The double flood washer comprises two V-shaped tanks, each with a
compressed air unit to agitate the water, and the produce passes through
both tanks by the action of a series of paddles, which finally elevate the
washed cut peppers on to an inspection belt so they may be examined for
traces of any seeds still left in the flesh.
Preparation Plant for Cabbage, Spinach, Leeks and Celery
Cabbage corers can be supplied with a single or double head. They are
manually fed and can be adjusted to take any normal size of cabbage.
A quartering machine is located alongside the corer, and this will cut
any cabbage into quarters when it is too large to feed into the impeller of a G-
type dicer, as cabbage is normally diced rather than sliced. Very few dicers
will accept a whole cabbage, and quartering imposes less wear and tear on
the dicer knives.
The main preparation plant requirement for spinach, leeks and celery
is a triple flood washer, as all these vegetables are notorious for retaining soil
in between leaves and follicles.
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Preparation Plant for Peas
A Tenderometer is an essential instrument for testing the maturity of
peas on arrival at the plant, and this should be synchronised for scale
readings with the Tenderometer on the farms.
A reel washer is required to rinse the peas on arrival.
A pneumatic separator will remove by aspiration any leaf or stalk left
in after the farm cleaning. The latter is now usually so good that factory
aspiration produces very little extraneous matter.
A floatation quality grader will separate the peas into positive quality
grades by specific gravity. A typical machine is illustrated.
A pea pump is an ideal medium for conveying peas hm process to
process in water. The rotor of the pump should be specially designed to
minimise damage and, although several makes are available, the author has
found that the Mono pump is very satisfactory. Special tough glass piping is
used for the conveying medium. A recycling tank is fitted with a grid for
separating out the peas and returning the water.
Preparation Plant For Beetroot
In addition to the hitherto mentioned washing and cleaning plant for
mots, beets require complete cooking before drying.
There are two alternatives: (a) standard autoclaves batch fed, or (b) a
Thermoscrew at 1 bar (am) pressure, giving a throughput of up to 2 tonnes
per hour continuously on a 20 to 40 minute cycle.
Preparation Plant Common to All Products
Steam pans, stainless steel, jacketed, capacity 400 litres, with electric
stirrer, are used for making up additive solutions for the blancher or for the
sulphite applicator spray (see illustration of integrated unit).
A dewaterer for removing surface water from products immediately
before entry into the dryer. This can be used as a sulphite applicator as well
by incorporating a water sparge pipe over the miprocating deck.
Services and Utilities
TABLE 3.2 lists the power, steam and water consumption required to
service the principal items of preparation plant in a medium/large sized
dehydration factory. TABLE 3.3 lists the ancillary plant and services.
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Additive steam jacketed pan assembly with stirrers
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TABLE3.2
Computed Demands on Utility Services for a Range of Pmparation Plant
Item Power(Installed1 Steam Water
KW Kg/hour lit./hr
Bulk Feeder 8/9 tons 2
Bulk Feeder 4/5 tons 1
Conveyor belts. Up to 7m 1.5
10-15m 2
Elevators 1.5
Dry Cleaning Reel 2 5ooO (if used as washer)
Destoner/ Washer 3 2000
Steam Peeler (complete unit) 6 350/500 (17bar)
Skin Eliminator 1.5 5o00/10,000
Abrasive Peeler: Batch 3 3000
Continuous 9 5o00
Dicer G Type 2.5
Slicer CC Type 1.5
Bean Slicer 2
Horizontal Destoner 2.5 2000
Cutter J Type 2
Slicer OV Type 2
Pneumatic Separator 3
Hot Water Blancher 5 500 1000/2000
Blancher (Draper Steam Type) 3
Thermoscrew (6mxlm dia.) 3 500 (1 bar)
Bean Declusterer 3
Vibratory Distributor 1
Bean Snibber 1.5
Steam Pan & Stirrer (400 lit) 0.5 100 400
Mono Pump (1001it/min) 1
Pea Pump System 2 500
Dewaterer-SO, Applicator or
Starch Applicator 0.5
Flood Washer (2 section) 3 1000/1500
Flood Washer (3 section) 4.5 1500/2000
Reel Washer 1.5 1000/1500
Brush Washer 2 1500/2000
Cabbage Corer (Twin Head) 2.5
Cabbage Quartemr 1.5
700
Elevator with Sparge Spray 1.5 1000
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Apricot Pitter (manual)
Apricot Pitter (automatic) 1.5
Pineapple Sizer (F.10) 2.5
Tomato Washer/Sorting Unit 3.5 15000
Box Tipper 1.5
'Cap Down' Shaker (Apricots) 1
Vibratory Screen 1.5
Precision Air Classifier 2.5
Turbo Mill UT 12 Model 20
Powder Sieve (Granules) 1.5
Sack Stitcher 1
Raw Vegetable Fluming Systems, Dryers, Conditioning systems (raw and
dried products), boiler plant, water supply systems, effluent systems,
dehumidification plant, site and factory lighting are excluded from the
above figures.
TABLE3.3
(Farm)
(Farm)
(Farm)
0.25 per unit
Garden Pea Mobile Viner, cleaning and chilling plant, pea tanks.
Green Bean Harvester (Tractor drawn.)
Green Bean Harvester (Self Propelled) - Alternatives
Economic Boiler (complete installation) Scaled to throughput.
Water Storage Tank (100,0001it/200,0001it)
Water pumps to plant, and water softening and treatment plant.
Plant Staging and Walkways.
Effluent Screens and Pumps.
Weighbridge (20 tonne)
Air Conditioning Plant (if required) for vegetable storage/offices
Dehumidification Plant (Packing and Milling area)
Power Transformer.
Factory Power and Light Installations.
Site Road Lighting
Standby Generator
Fans/Cooling Equipment for vegetable store where applicable.
Platform Trucks for Factory internal use.
Forklift Trucks
Factory Transport, - Trucks - Pick-up.
Staff cars.
Insectocutors.
Laboratory Equipment.
Workshop Tools.
Canteen Equipment.
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Office furniture and equipment.
PVC bins and basins for factory internal use (vegetables).
15 cwt vegetable bulk boxes.
Small Fieldboxes (1Wkg capaaty)
Staff Housing (where applicable)
Tenderometer (F.M.C.)
The above items must be taken into account in computing the capital
requirements in any project, as and where relevant.
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