6 Dehydration of Vege ta b I es The vegetable cultivars quoted in the following process data are, in the main, those bred in temperate climates, the USA and Western Europe and, in the case of pulses, the Antipodes. However, with the growth of dehydration in the developing countries, with tropical or subtropicalclimates, these regions, along with Eastern Europe, Egypt and China, who have had a dehydration industry for many years, have, through their Horticultural Institutes and Ministries of Agriculture, developed indigenous varieties which have been processed with considerable success. It may not be possible to identify all these varieties but in the author’s experience, great assistance has been afforded by the field officers working with these Horticultural Institutes in setting up field and seed trials for the benefit of processors, and they are becoming increasingly knowledgeable in the characteristics required in vegetables for processing. They have afforded, also, valuable information on the infrastructure required for setting up a processing plant, along with the disposition of labour, local building requirements for food factories and the pattern of irrigation practices. The processes set out assume an intermediate size operation with a reasonable measure of automation but, of course, in each case the throughput may be cut down to meet capital budgeting requirements, and whilst most of the preparation plant is geared to a raw throughput of some 1.5 to 3 tonnes per hour of prepared material or 300 to 350 tonnes of raw produce per week, adjustments can obviously be made, introducing more hand labour in 121 preparation and using Stove or Through-Flow Tray Dryers instead of a Conveyor Band Dryer, either single or multi-pass. Whilst a product-mix should be arrived at to give the maximum number of days work in a season, it is wise to concentrate on those vegetables which are available for several months of the year, either from seasonal sowings, or by having storage facilities at the factory or farm. Too many change-overs from product to product are costly, often entailing moving plant around, but what is more important is knowing the market demand for those vegetables for which the climate and growing conditions are ideal. HORTICULTURE It is difficult to guide the processor in horticultural procedures, as climate and soil conditions will vary considerably from region to region. The company agronomist must assess all the requirements and problems on the spot, and in a new venture it is absolutely essential to carry out field trials for every vegetable to be processed. However, the author has appended some horticultural guide lines for seven of the more popular vegetables grown for dehydration, and these follow the processing data in this chapter. The guide lines are based on actual field trials and commercial scale cultivation in several locations varying from temperate to subtropical climatic conditions. In most cases irrigation was available, either contour or overhead spray. GREEN BEANS (1) Flow-Sheet Feed to Line I Pneumatic Separator I Washing I Cluster Cutting (only for machine harvested beans) I Inspection I Snipping I Inspec tion I Blanching I22 I Sulphiting I Slicing (long cut) I Dewatering I Drying I Conditioning I Screening I Inspection I Packing (2) Varieties (3) Product Handling The bean pods are either harvested by hand or, in the case of large acreages, by mobile bean harvesters. They are fed to the line in a bulk feeder from where the pods are delivered into a pneumatic separator to remove extraneous matter. They are then transferred to a reel washer which, in the case of machine harvested beans, feeds in to cluster cutters, to 'single' any beans not separated from their stalks in the harvester. This machine is not necessary for hand harvested beans. After inspection on a conveyor belt, the beans are conveyed on a vibratory trough belt and ploughed off into a battery of snippers. The number of snippers willdepend on throughput,as each machine will handle about lOOOkg per hour. At the exit end of each snipper an unsnipped bean removal reel takes care of any beans not topped and tailed and returns them to the snippers. Snipped beans are then visually inspected on a conveyor belt and delivered into the blancher. This can be either a hot water or steam type, depending on what other products are to be catered for. For example, if cabbage or leaf vegetables are included in the product mix, it would be advisable to opt for steam blanching as this is more suitable for brassicas. Sulphiting is effected by pumping from sulphite make-up pans into the blanching water, in the case of hot water blanching. If steam blanching is Tendergreen, Processor, Bush Blue Lake I23 used, sulphiting is carried out in a sulphite dip tank situated at the discharge end of the blancher, and the solution of sodium sulphite is made up in the pans alongside. Anhydrous sodium sulphite is always used for green vegetables and sodium metabisulphite for root vegetables, where sulphiting is permitted under prevailing Food Laws. Whole beans are fed on a vibratory conveyor to slicing machines (long cut) with a capacity of 2000kg per hour each, the slicing taking place after blanching to prevent the seed of the pod being washed away in the blanching process. After dewatering, the cut beans pass into the dryer, thence to conditioning bins. The dried slices are elevated to the screen for sifting to remove broken pieces and fines, and then to the final inspection tables. Packing should be in poly-lined cartons or drums, rather than paper bags, to avoid breakage. (4) Drying Conveyor Band dryer scaled to throughput Temperatures (input): 85"/ 77"/ 60°C Conditioning: 5Oo-52"C Dry to 6% Overall ratio: 13.1 Drying ratio: 9.1 Cultivation Guidelines for Geen Beans (1) Sowing: 150kgperHa. Sowinsinglerows7.5-lOcmapartat4lcmcentres. Sow50mm deep in fine tilth. (2) Fertilisers. On irrigated land use N40/P80/K60 plus 2.5 tonnes of organic per Ha., if available. (3) Herbicides. Preforan or Granoxone or Dachtal. (4) Pesticides. Dimethoate or Diazinon; for caterpillar attack, use Folithon or Diazinon. (5) Disease Control. Botrilex against Southern Blight or Root Rot. Afucan or Benlate every 7 days against powdery mildew. Kocide, Perenox or Cupravit against bacterial blight or rust. (6) Maturity Pick every second day to avoid over-maturity. 8mm is the maximum pod diameter (measured across a section of the bean) for processing. Harvest is about 60-70 days from sowing. Plant population: 430,000 per Ha. I 24 BEETROOT (1) Flow-Sheet Semi - Continuous Process I Feed to Line I a Autoclave cooking Destoner-Washer Batch Process Semi-Continuous Pressure Cooking Washing 2 Skin Removal I Inspection I Cutting I Dewatering I Drying I Conditioning I Screening I Inspection I Packing (2) Varieties (3) Product Handling Beets should be selected 50-75mm in diameter, with the tops wrung off (not cut off) at the farm. Care must be taken to avoid bruising and 'bleeding'. From the bulk feeder they pass through a dry cleaning plant to remove soil, then to a destoner-washer or alternatively a flood washer, if free of stones. Two options are open to the processor: (a) to feed the beets into a batch thermoscrew operating at 1.2atm steam pressure. A Thermoscrew 6m long by lm diameter should batch-cook young beets in a 20-40 minute cycle at a Detroit Red Globe I25 rate of 1.5-2 tons per hour; (b) the second alternative is to cook the beets in batches in an autoclave, or a series of autoclaves according to quantity of input. Again pressure will require to be at 1 to 1.2atm. Cooling from the semi continuous cooker will be in a slat washer reel and, if from autoclaves, the cooling water will be applied to the bottom of the autoclave and allowed to circulate until the pressure has dispersed and the autoclave baskets can be removed. The cooked beets, when cool enough to handle are fed on to a stainless steel belt where the skins are removed by hand. The batch system is the one most often used, as a continuous pressure cooker is a very expensive machine. Stainless steel belts should be used when handling beets, as rubber or PVC belts will stain badly and are difficult to clean. The red pigment is betanin, which will leach out if the beets are subjected to washing after peeling and dicing. This should be avoided. Before the beets are transferred to the cutters, any root or fibre remaining should be removed on a second inspection belt, or this can be done by the skinning operators, if the belt is sufficiently long to accommodate both functions. It is most important that the beets are fully cooked before cutting and drying. Some processors have attempted to peel beets in a standard steam peeler but the short residence time suitable to soften the skin of vegetables, such as carrots and potatoes, is insufficient to soften the beet to the centre of the root, and partly cooked beets when reconstituted after drying are not acceptable. When the skin is removed, therefore, it is necessary to check that the beetroot flesh is tender to the centre, and it is only by extended cooking under steam pressure, either in autoclaves or a semi automatic steam peeler with a controlled residence time, that the right tenderness can result. Peeling and trimming losses will amount to 20 - 30 percent. Beet is usually cut into 9.5mm dice if used subsequently for pickling. No blanching or sulphiting is required. After dewatering the dice, they are fed into the dryer. (4) Drying. Conveyor Band Dryer scaled to throughput, or Stove dryers. Inlet temperatures: 99"/ 82"/ 71 "C Condition in Bins to 5 - 6% at 54" - 57°C Raw moisture 89% Overall ratio: 14:l to 15:l Drying down ratio: 7:l Note. A.K.Robins &CoIncof theUSA,and alsoFoodMachinery Corporation, make suitable semi automatic beet peeler-cookers. The Robins machine is particularly suitable, as the time under steam pressure can be extended as I26 desired to achieve complete cooking, and it incorporates a second tank where rubber rollers rub off the skin without damage to the flesh. Where autoclaves are used, these can be the standard canner’s horizontal type, with front loading. The standard retort crates should not be used, however, as the depth of beets will be too great for the heat to penetrate into the centre of the mass and proper cooking will not take place. Small stainless baskets with perforated bottoms should be used, of suitable size to fit in layers inside theretort crates but spacer battens should be used between each row of the small baskets to allow a free flow of steam around and through the product. In this way the residence time for cooking and skin softening can be substantially reduced and an even penetration of heat obtained. BELL PEPPERS (1) Flow-sheet Feed to Line I Double Flood wash I Splitting I Deseeding I Double Flood Wash I Inspection I Cutting I Sulphiting I Drying I Conditioning I Screening I Inspection I Packing I27 (2) Varieties. (3) Product Handling Peppers may be processed whilst green, or can be left to ripen to red. Intermediate greedred peppers are sometimes processed but do not command the top market price for the dry material. The peppers are fed from field boxes into a bulk feeder, then elevated to a double flood washer which has compressed air fed into its base to aerate the water. Whole washed peppers are fed to a three channel inspection belt where they pass down the outer lanes for deseeding, and the halves are then delivered down the centre channel to a second flood washer which washes out the remaining seeds. Cleaned peppers are elevated from the flood washer on to an inspection belt where any residual seeds or pith are taken out manually. It is possible to core and deseed peppers by machine but, unless the shape and size are very regular, these machines are not 100 percent effective, and manual handling is often preferred. If tomatoes are included in the product mix, then a tomato washing and sorting line can be used for both products as indicated in Chapter 3. The peppers are then elevated toa J typecutter, which is particularly suitable for peppers, leaf vegetables and leeks. After cutting into flakes with the J cutter (capacity 2000kg per hr.) the product is elevated into a sulphiting bath with the solution of sodium metabisulphite controlled to give a residual level of 1250ppm (+/- 250ppm) in the end-product. After dewatering, the flakes pass to the dryer, then to conditioning bins. After drying, the flakes are elevated to a vibratory screen for removing fines, and thence the main product is fed by vibratory conveyor on to an inspection belt. The number of belts will depend on required throughput. Each 7 metre belt should handle 1.5-2kg of product over the total area of the belt at any one time. At a belt speed of 4 metres per minute, 60-80kg of product can be handled per hour, per belt. (4) Drying Conveyor Dryer or Stove or Tray Dryer scaled according to a desired throughput. Input temperatures 85°C in first stage reducing to 50°C at end of cycle. Conditioning at 52" - 54°C. Dry to 6% to 7% Ratio overall (Raw material as received: dry = 22:l.) Drying Down ratio (Prepared material: dry = 14:l.) Yo10 Y. - California Wonder. - Bell Boy. I28 Cultivation Guidelines for Bell Peppers (1) Sowing Nursery Bed spacing: 6.5cm. Plant out: 23-30cm apart in 75-100cm rows (2) Fertilisers Apply 500kg per Ha of 12:12:17+2 at planting and side dress at 4-6 week intervals with 250kg per Ha of Sulphate of Ammonia or 12:12:17+2. (3) Herbicides Apply Dymid liquid formulation at 11 litres per Ha. (2kg active) or 2kg Diphenamid 8OW (Dymid), either pre or postemergence, to clean ground. (4) Pesticides Diazinon 60 EC against Leaf miner: Thrips: Aphids Endosulfan against flea beetles and caterpillars. (5) Disease Control Kocide 101 against bacterial leaf spot. Dithane M45 or Antrocol against mosaic virus. If virus is severe, uproot affected plants. (6) Maturity California Wonder should be picked green but allowed to bc fully mature before harvesting. If picked too young the fruit will wilt. Yo10 Y is left to mature to bright red. Harvesting is 12-14 weeks from sowing/planting, onwards. Plant population 30,000 per Ha. CABBAGE (1) Flow-sheet Feed to Line I Trimming I Coring / Quartering I Rod washing I Flood Washing I Dicing I Steam Blanching I I29 Sulphiting I Dewatering I Drying I Conditioning I Screening I Inspection I Packing (2) Varieties As cabbage is now used mainly as a constituent in soups, both for flavour and eye appeal, it is necessary to select cultivars of bright green appearance when reconstituted. Another important requirement is that the head should be compact and ideally the core should not exceed 7 - 8 percent of the total trimmed weight. Very heavy trimming losses can arise from heavily cored ball- headed varieties, such as Primo and Winnigstadt, and these should be avoided. Small compact heads, such as Celtic, Ice Queen, and January Queen are useful Savoy types with good colour. Hispi and Offenham are good early varieties, and Wiam a dark green mid-season type. Cabbage is grown almost worldwide and there will be many indigenous varieties which could process well, subject to the parameters set out on colour and absence of heavy core. Dry matter is all important and 9 - 11 percent total solids is a figure to be aimed at when selecting raw material. (3) Product Handling Cabbage is brought to the factory in crates or tote boxes, and special attention should be given to the condition of these in the reception area, to ensure that wooden containers are not splintered. Splinters of wood can cause damage to cutters, apart from contaminating the product. Cabbage nets are also a hazard as they tend to shed fibres, which are difficult to detect in the dry product. Cabbage should never be stored for more than ten hours at the factory before processing. As much trimming as possible of outer leaves should be done at the farms to avoid bringing extraneous waste matter into the factory. The first operation is to trim the cabbage of its four outer leaves on a suitable conveyor I30 belt. Where a lot of knife work has to be done, it is advisable to have a narrow hardwood bench running along the length of the trimming belt - on both sides - to prevent damage by knives to the belt fabric. After trimming, the heads are conveyed on to a coring machine, preferably one with two heads, thence to the quartering machine which cuts the head into 4 segments. These pass through a rod washer, and then through a double flood washer, in which the aerated water will disperse any grit or soil trapped between the leaves. Cutting follows, and cabbage is now mostly diced rather than shredded in view of its use in soups or other composite vegetable meals. The size of the dice will depend on market specifications. Blanching is preferably carried out in flowing steam, either in a Thermoscrew-type or a Draper or belt conveyor blancher. Sulphiting is carried out in a sulphiting dip tank, or on a reciprocating screen over which sparge pipes spray on the sulphite solution. The latter is made up in an adjacent steam pan fitted with an electric stirrer. Sulphite solution is made up from sodium sulphite (anhydrous) to achieve a level of 2000ppm in the dry product. The addition of sodium carbonate, bringing the alkalinity of the liquor up to pH 8.5 - 9, enhances the colour of the product but this is optional if the cabbage has a bright natural green colour. The dice pass over a dewaterer before passing to the dryer. A lot of surface water adheres to cabbage, and a thorough dewatering will make the drying operation much easier. Some plants centrifuge cabbage after blanching and before drying but this tends to revert to a batch process and breaks the flow into the dryer. (4) Drying Conveyor dryer scaled to desired output. Temperatures (inputs) through zones: 80"/75 "/65 "C Conditioning: 50" - 52°C Moisture down to 5% maximum, as cabbage is hygroscopic. Cabbage is easily damaged by high drying temperatures and the above levels should not be exceeded, particularly in the middle and end heat zones. The phenomenon of 'browning' in cabbage arises from improper blanching, sulphiting or drying. Browning arising from processing faults must not be confused with scorching by high temperature in the dryer, although the appearance is similar; the stalk fraction being more affected than the leaf. It is thought that the condition is caused by the heat decomposition of certain soluble constituents in the raw cabbage. There is a big shrinkage loss in drying cabbage, and it is necessary to have a dryer of ample drying capacity at relatively low temperatures, 131 otherwise the dry output will fall below an economical level. The dried cabbage may be aspirated at the time of screening to remove any excessive stalk content. This breaks up the particles which may have a tendency to mat together. Packaging should preferably be in air-tight drums, with 500 guage polyethylene liners. Nitrogen flushing is also recommended. Drums give better protection than poly-lined sacks, as some product abrasion takes place in transit with the latter. Ratio: Overall 17:1 Drying 10.5:l Tray loading cabbage prior to cabinet drying Cultivation Guide Lines for Cabbage (1)-Sowing Direct drilling: 1.7kg per Ha. Transplanted: 550g per Ha. Final spacing: Early: Mid-Season: 37cm in rows by 30cm centres Late: (Savoy):-60 cm in rows by 60 cm centres (2)Fertilizers: On irrigated land use N100:P40:K60 plus 2.5tonnes per Ha organic (3)Herbicides: -Propachoor (Pre-emergence) or Dynid. (4)Pesticides: -Dimethoate: Hostathion: Fundal: Galicron: Prosuel: Princidid:-Diazinon. (5)disease Control: I32 Calomel Dust and Garden Lime on transplanted roots if Club Root is endemic. Benlate against Leaf Spot. (6)Maturity: -Cut before ‘cracking’ occurs. If rain follows cracking, heads will rot. Harvest is 12-15 weeks after drilling, or 14-17 weeks with transplanted crops. About one third of the above time is in the nursery bed. Plant population:-Mid-~eason:-87,000 per Ha -Savoy:-27,000 per Ha CARROTS (1) Flow-Sheet Feed to Line I Dry Cleaning I Des toner-Washer I Flash Steam Peel I Skin Elimination I Inspection Trim I Cutting I Inspection I Blanching I Sulphiting or Starch Dip Dewatering Drying L I Conditioning I Screening I Inspection I33 I Packing (2) Varieties Colour and high total solids are the most important factors in selecting carrots for dehydration. Up to the 1970's Chantenay was perhaps the most favoured variety in Europe because of its stump rooted shape, which made for economy in dicing. It was practically coreless and had an orange-red colour, which was reasonably bright when dehydrated. It did not prove very hardy in the winter in Europe and rarely survived without frost damage beyond December, when processors reverted to the more hardy Norfolk Giant and Danvers. Chantenay also failed to reach full colour if not allowed to mature properly. The author experienced a severe problem in Cyprus in the early 70'5, when a particularly wet winter had encouraged good growth in carrots and potatoes (even the early spring potatoes produced tubers 13-14cm long and 7-8cm in diameter) but the crop of Chantenay carrots being grown on contract for a multi-national processor in the UK failed completely to develop an acceptable red colour, due to the non development of the carotene in the early stages of growth, following a very cool wet spring. Today, the selection of carrots for dehydration has become a specialist exercise for the seed breeder and several useful cultivars now being produced come from Dutch seed breeders, and the following have been favourably regarded by European dehydrators: the suffix RZ indicates the seed breeders - Rijk Zwaan of Holland. Karotan RZ Bordeaux RZ Kartal Tosto RZ Furon RZ These are related by a succession of cross breeding to a German variety, Kieler Rote, which the author introduced into the UK in the late 1960's for field trials but which, although they meet the parameters of a bright scarlet colour and very high solids, failed in context of its long tapering shape, which made it uneconomic for dicing. The above new varieties, now bred to the Kieler Rote colour characteristics, should provide an excellent choice for the dehydrator. In the USA the Ventura type carrot is used successfully. Ventura is, however, a region and not a specific cultivar but several varieties which meet the colour and solids requirements are available from Californian seedsmen. (3) Product Handling The removal of the tops and crowns of the carrots should be carried out on the farm or at a preprocessing washing and 'topping' station, to avoid I34 bringing tops and extraneous material into the factory processing areas. Once 'crowned', however, the carrots must be processed without delay, otherwise they will become rubbery and their quality will deteriorate. Removal of the crowns will create a 10 - 11 percent weight loss, according to the size of the root, and this will be reflected in the factory price, as will the labour cost of the out-workers. The carrots will be fed from tote boxes into a bulk feeder, unless a fluming system is used, in which case they will pass through a prewasher in the flume discharge pit, be separated from the fluming water, and then elevated into the bulk feeder in the factory. If thecarrots havebeen prewashed, then the dry cleaning reel is not required, and they will pass on to the destoner. If the carrots are delivered dry into the bulk feeder, they will pass through the dry cleaning reel and then to the destoner-washer. Peeling is preferably by 'flash' steam peeler at 17atm pressure and the skin is then removed in a skin eliminator. If lye peeling is used, this must be followed by passage through a brush washer. Peeled roots are then inspected on a 'merry-go-round' conveyor for trimming where necessary, then elevated to a G Dicer, set for 9.5mm dice, half dice or flakes 9.5 by 9.5 by 2mm. For instant reconstitution soups, the cut may have to be reduced to 6 by 6 by 2mm. It is normal to blanch in a hot water blancher, with the additives (SO, and buffering agents, such as sugar and salt) being metered into the blancher at a prescribed rate to sustain an SO, level of 1200ppm in the end product. The use of SO, in carrots has now been superseded in American factories by using a steam blanch in a Draper-type belt blancher followed by a dip in 2 percent food grade corn starch. This retards colour and quality loss, and is regarded as better than sulphiting only but their specification usually permits a maximum of 500ppm of SO, in the dry product, or less than half the European level. Dehydrated carrot was originally packed in nitrogen-flushed hermetically sealed tins against Armed Services indents, as it is recognised that the colour deteriorates rapidly after 3 months storage in poly-lined containers - the dice turning pink and giving off an odour reminiscent of violets. The starch dip method has partially overcome theoxidation problem but it is necessary to hold the product in cool storage (under 5°C) if it is required to be stored for 6-9 months. The end moisture also affects durability, and should not be more than 5 percent. (4) Drying Conveyor dryer scaled to a throughput of 2 tonnes per hour upwards. Through-flow or stove dryers for 500kg per hour upwards. Temperatures (inlets) through zones: 104 "/ 93"/ 88°C. I35 Conditioning: 50" - 52 "C Moisture maximum 5% Raw moisture basis 90% Overall Ratio: 15:l Drying Ratio: 9:l The Overall Ratio is based on the factory gate weight, ie, with tops and crowns removed to the dry weight. Cultivation Guide Lines for Carrots (1) Sowing To produce large roots : sow 1.7kg per Ha. 50mm spacing in single rows at 37cm centres. Deep soil cultivation. (2) Fertilizers 260kgperHaof 12:12:17+2beforeplantingandrepeat as a topdressing ifleaf shows sign of yellowing. Organic 1500kg per Ha. (3) Herbicides Pre-emergence: Prometryn 50 WP at 2.5kg per Ha. Post-emergence: Herbicidal oil (Kerosene) 500-750 litres per Ha., after first true leaf appears. (4) Pesticides Diazinon or Dimethoate against aphids and leaf miners. (5) Disease Control Spray regularly with Daconil or Benlate against alternaria and leaf spot. (6) Maturity Roots should be allowed to grow to 40-45mm minimum across the crown. Do not lift until carotene is developed and full colour is achieved. Ensure that the crown is covered by the soil to prevent greening. Harvest is about 14-1 6 weeks after sowing but lifting can continue for several weeks after this. (7) Plant population 530,000 per Ha. CHILLI PEPPERS (1) Flow Sheet Feed To Line I Washing I Inspection I Shredding I I36 Drying I Conditioning I Inspection I Packing (2) Varieties Anaheim Long Green Chili (Californian) Jalapeno Green (Mexican) Floral Gem Grande Yellow /Red (Californian) Birds Eye Red (miniature - 13-19mm long) (Africa - Papua). (3) Product Handling Only fully mature pods are picked at time of harvesting. They are brought to the plant in bulk or tote field boxes and fed into a feed hopper. They are washed through a flood washer or washing reel, inspected on a conveyor belt and fed toa J type cutter for cutting into 25mm slices. Birds Eye small red chillies are dried whole, usually in the sun, or they can be artificially dried. The cut or whole peppers are fed into the dryer for low temperature drying, conditioning, aspiration, inspection and packing. Dried chilli peppers may be ground down for chilli powder but for this purpose they must be dried to 3-4 percent. (4) Drying Conveyor or Stove Dryer according to scale. 6 hour cycle for slices - 10-12 hour for whole. Temperatures (input) through zones: 71 "/65"/62 "C Conditioning: 49 "-50 "C Moisture down to 6-7% for sliced chillies. Raw Moisture = 80% CELERIAC (1) Flow Sheet 4% for whole (small) Drying Ratio = 5:l Overall ratio: 6:l Feed to Line I Dry cleaning I Destoner-Washer I Steam Peeling I I37 Skin Removal I Inspection I Dicing I Blanching I Sulphiting I Dewatering I Drying I Conditioning I Screening I Inspec tion I Packing (2) Varieties Smooth skinned root cultivars: Giant Prague - Alabaster (3) Product Handling As in the case of many vegetables, much of the rough preparation should be done externally to the factory, particularly as celeriac has a considerable amount of leaf and stalk. The latter should be cut well back to the root crown as, whilst some of this can be used in the fresh state for salads, it serves little purpose for dehydration. The trimmed roots are therefore fed into a bulk feeder and elevated into a dry cleaning reel. The roots pass into a washer- destoner and on to the steam peeler. Peel is then removed in a skin eliminator and the roots pass on to an inspection and trimming belt. Cleaned roots are elevated to a G model dicer (capacity up to 6OOOkg per hour for lOmm dice). Alternatively the roots may be cut into strips 40mm x 6mm x 6mm. Blanching may be carried out in a hot water blancher, in which case the sulphite is fed from a make up pan and metered to give the requisite level of SO,. Alternatively a steam blancher may be used and the sulphite solution sprayed on to the diced product on leaving the blancher. When setting up a root vegetable line, it is probably advantageous to opt for steam blanching, provided potatoes are not included. Potatoes release considerable amounts I38 of starch after cutting, and water blanching permits this to be removed from the surface of the blanching liquor by arranging a flow of hot water continuously through the blancher. On the other hand water blanching leaches solids from carrots, swedes, turnips and all green vegetables, and consequently better drying ratios are achieved if steam blanching can be used in these cases. If potatoes are a major part of the product programme, however, then hot water blanching may have to be used in the root vegetable line, as the expense of two blanchers in parallel may not be justified. 5-6 minutes is required, adding up to 1 percent citric acid in the blanching liquor to assist whitening. This is combined with the SO, treatment in hot water blanching. The blanched material is dewatered before passing to the dryer, then to the conditioning bins. Screening, sorting and packing proceed as for other vegetables. (4) Drying Conveyor Dryer scaled according to desired throughput. Temperatures (input) through zones: 104"/ loo"/ SO"/ 75"/ 50°C through the zones. Conditioning at 50"-55 "C Overall ratio: 15:l Drying ratio: 9.5:l CELERY (Leaf and Stem) (1) Flow Sheet (subject to acceptable trimming losses). Feed to Line I Flood Wash I Trimming I Flood Wash I Inspec tion I Cutting I Blanching I Sulphiting I Dewatering I39 I Drying I Conditioning I Aspirating Kibbling\Milling Inspection I Packing (2) Varieties (White) Lathom or Golden Self-blanching (Green) Pascal or Utah 52-70 (3) Product Handling Celery should undergo a good washing process on the farm to avoid bringing unwanted soil and dirt into the factory. It should also be well trimmed down to the root and have coarser outer leaves removed, leaving very little green top. The field boxes of trimmed and washed celery are tipped into a bulk feeder, from where it is elevated into a double flood washer. After washing under pressure the roots are elevated on to a trimming belt, or ‘merry-go- round-system’ conveyor where any discoloured stalks or leaves are removed. Large roots are cut longitudinally so that no root is greater in diameter than 70mm. This assists removal of soil in the second wash. Trimmed celery then passes through a second double flood washer and on to an inspection conveyor. Thence it is conveyed to a J type cutter, or alternatively a Model OV Transverse Slicer. The celery should be cut into 9mm squares on the former J machine or transverse slices on the OV. The green part is aspirated out after drying. The celery pieces are blanched in steam for 2 minutes, and then dipped in a sulphiting tank for a few seconds in a solution of SO2 and 1 percent citric acid. The level of SO2 concentration is such as to give a final concentration of 1OOOppm in the dry product. Up to this point, it is essential that all equipment shall be of stainless steel to prevent blackening of the product. Thecut celery is dewatered and conveyed to thedryer, then conditioned. The bins of dry material are fed into a precision air classifier to separate the green leaf from the slices or squares. If the celery is required for powdering or kibbling for soup, it is diverted to a Turbo-Mill or Kibbler - otherwise on to inspection tables prior I 40 to packing. Conveyor Dryer scaled to desired throughput. Temperatures (input) through zones: 82"/ 76"/ 65°C Conditioning: 5Oo-52"C to 6% moisture Overall ratio: 221 (for well trimmed roots) Drying ratio: 14.2:l GARLIC (1) Flow-Sheet (4) Drying Feed to Line I Bulb Cracking I Screening 1 Aspiration I Flood Washing I Dewatering I Inspection I Slicing I Drying I Screening I Aspiration I Inspection Milling for Powder - 250 microns Kibbling I Packing (2) Varieties (3) Product Handling The garlic bulb, which may contain from &36cloves, is broken into individual California Late, California Early, Creole or indigenous 141 cloves by passing between rubber-covered rollers that exert enough pressure to crack the bulb without crushing the cloves. The loose paper shell is then removed by screening and aspiration. The cloves pass through a flood washer to float off the root stubs. After dewatering, the garlic is inspected, sliced and loaded on to trays for drying. After drying the pink skin, which adhered to the fresh clove, will have been loosened sufficiently to be removed by screening and aspirating. After inspection, the clove slices can be kibbled down to a smaller particle size, or milled in a Turbo Mill fitted with a 250 micron screen. (4) Drying Stove or Through-Flow dryers are used Temperatures (inlets) 70°C reducing to 50°C Moisture down to 5% for kibbled and 4% for powder. Preparation losses will be approximately 40% - 600kg prepared material from each 1 tonne received. Overall ratio: 4:l Drying ratio: 2.4:l Note: Much of the garlic processing plant has been designed by the major processors themselves, particularly in the USA where production is in the main confined to California, and the larger onion processors. Horticulture Yields in the USA are up to 9.5 tonnes per hectare. The garlic is cured on the field in windrows after lifting. Bulbs are topped and sorted (to remove diseased bulbs) on the field. Sometimes grading precedes delivery to the factory. The bulbs may be stored but at more than 70 percent RH they may start to mould. LEEKS (1) Flow Sheet Feed to Line I Inspec tion I Flood Washing I Cutting 1 Inspec tion I Sulphiting I I42 Dewatering I Drying I Conditioning I Aspiration I Screening I Inspection I Packing (2) Varieties Autumn Giant, Goliath Super RZ, Bastion RZ, Giant Musselburgh, American Flag, Autumn Mammoth Carantan, Winterreuzen, Giant Winter, and many indigenous varieties having thick stems and a good proportion of white bulb to green top. (3) Product Handling Like celery, leeks also require a considerable amount of cleaning and trimming on the farms. The roots should be cut right back to the butt of the bulb, and only about 30 percent of the green leaf should be left on the bulb. Further cutting back may be necessary if the leaf is discoloured. In effect, the leek should be prepared on the farm to the quality expected on the fresh market in context of washing and trimming back the green leaf. This is essential to avoid extraneous matter being brought into the factory, and it is far better to leave vegetable waste on the land than to create a waste disposal problem in the factory working areas. If necessary, a premium should be paid to the grower for this extra service. The trimmed leeks are fed promptly from the bulk feeder to the inspection belt for final trimming and examination, and it is important that the leeks are handled quickly as they are a perishable vegetable and will not hold well once lifted. If storage is necessary leeks can be held for a limited period at 0°C at 90 - 95 percent RH. The leeks pass through a double flood washer to ensure that any dirt or silt still remaining in the crotch of the leaves and follicles is washed away by the aerated water in the two washer tanks. If the leeks are very thick stemmed, it may be necessary to split them longitudinally on the inspection belt before the washer. A J type cutter is used with knives set to produce flakes of a predetermined square size, the thickness being that of the leaf and follicles. I43 Alternatively they may be diced to 9.5mm. Sulphiting follows in a sulphite applicator, the solution being made up in an adjacent pan at a concentration to achieve 750-1000ppm in the end product. The concentration of the liquor is 1 - 1.5 percent. After dewatering, the flakes proceed to the dryer. Green and white flakes are not separated at this stage. After drying, the flakes are transferred to the conditioning bins. Before screening the product is then fed into an aspirator which can be accurately adjusted to separate the green leaf from the white bulb flakes. Screening will remove fines and, after a final inspection, the product can be packed. If required the product can be milled for powder on a UT 12 Turbo Mill fitted with a 250 micron screen, as there is a good demand for powder as a soup ingredient. (4) Drying Conveyor Band or Stove Dryer, scaled to throughput. AThrough-flow Dryer may also be used for medium scale operation. Temperature (inlets) through zones 82"/ 76"/ 65 "C Conditioning: 50" - 52°C. End moisture 5 - 6 % Overall ratio 14:l Drying ratio 8:l - with a raw moisture of 88 % Cultivation Guide Lines for Leeks (1) Sowing Nursery Beds: Drill 2.5kg per Ha, Transplant 15cm apart in single rows at 45cm centres. (2) Fertilisers A rich soil is essential, with 1000 - 1500kg per Ha. organic manure ploughed in before drilling/planting. Otherwise applications of artificial manures is as for onions. (3) Herbicides Pre-emergence: Dachtal W75. Post-emergence: Nitrofen 14 days after emergence of first leaf. (4) Pesticides Diainon, Leptopros, Permethrin. (5) Disease Control Benlate, Kocide 101 (6) Maturity Drillsshould beregularlyearthed up tofacilitateblanchingof the bulb. They should not be lifted until the bulb is upwards of 40mm in diameter. The root and two thirds of the green top should be trimmed off in the field when lifting, before delivery to the plant for processing. Plant population: 143,000 per Ha. I 44 MUSHROOMS (1) Flow-Sheet Feed to line I Washing I Inspection I Cutting I Blanching I Drying I Conditioning I Screening I Inspection - Milling (boletus edulis) Packing (2) Vareties (3) Product Handling Both types of mushroom are handled more or less in the same way, although the wild or field mushroom is picked fully open, exposing the dark pores on the underside instead of the gills characteristic of the cultivated mushroom, or champignon. Thorough washing is necessary in a reel or drum washer to remove all traces of soil. Inspection on a conveyor belt follows. The champignon-type mushroom is usually sliced in a CC Slicer to 0.8 - 3.2mm thickness. If the mushrooms are large then a G type dicer set for 6.4mm dice is favoured. In thecaseofBoletus edulis,eitherasmallcutisrequired if theproduct is going to be used as a whole particle ingredient in dried soup mixes, or a random cut if thedried material is to be milled for mushroom powder, which is also used as a base for mushroom soup. Whole mushrooms of whatever size are rarely air dried, as the drying cycle is too protracted. With both varieties, the stems are left on, unless there are some of the root fibres left, in which case the latter should be trimmed off on the inspection table but Agaricus campestris (cultivated mushroom) Boletus edulis (field mushroom) I45 anything up to 1.5in. of stem may be left on. Blanching in flowing steam or hot water takes from 2 to 5 minutes. After drying and conditioning to 5 percent moisture, the product is inspected and packed, or diverted to a mill for grinding to powder. The particle size should be 250 microns (60 BSM sieve). Air drying never produces a really first class product suitable for use as a straight vegetable for grilling or frying, and this quality can only be achieved by freeze drying. On account of the high value of the raw material and the price obtained for the end-product, this is one of the very few vegetables which will support the high cost of this process. (See Autec Process in Chapter4). However, if colour and presentation is a secondary consideration and a considerable percentage of the product is going to be milled for powder, then air drying can be considered. A major problem with mushrooms, by the nature of their cultivation, is a very high total bacteria count, and excessive levels of yeasts and moulds. This can be circumvented to a degree, by reversing the heat zone temperature in the dryer, ie, controlling the inlet temperatures in the usual 'hot' zone to not more than 65 "C and finishing at a higher temperature of 80°C. In this way the bacterial level can be substantially lowered. Mushrooms are about 93% moisture, and drying should be down to 5% end moisture. Overall ratio 16:l Drying ratio 14.5:l GREEN PEAS (1) Flow Sheet (4) Drying Farm Vining I Dry Cleaning I Pneumatic Separation I Washing I Cooling Factory Washing I I46 Pneumatic Separation I Quality Grading I Inspection I Scarifying I Blanching I Dewatering I Drying I Conditioning I Aspiration I Screening I Inspection I Packaging (2) Varieties Early: Sparkle Banff Main: Scout Tristar Pujet Markardo (3) Product Handling (a) Farm handling It is invariably essential, with the general use of viners nowadays, that the grower assumes responsibility for the greater part of the precleaning and cooling process, which enables the processor to handle peas on a 24 hour a day basis, without deterioration of the raw peas held in bulk at the factory. Some years ago it was necessary to process vined peas within two hours of their being shelled. To do this, podding machines, and later viners, were installed as static machines outside the factories, and the cut haulm was transported on bogies fiom the farms, and podding or vining was controlled to handle peas with a minimum of delay once the peas were shelled. The transport of vine/haulm and the disposal of the threshed haulm eventually proved so cumbersome and costly, that mobile viners were developed, whereby the shelled peas were collected in trucks on the field running I47 alongside the vining drums, and the waste haulm was discharged from the rear of the mobile viner on to the field and subsequently ploughed back into the soil. Mather & Platt’s super mobile viner working in the field. Obviously some solution to the holding of shelled peas in bulk had to be found to prevent the rapid spoilage that arises from the heat generated in the pea which has been subjected to stress by the beater-paddles in the viner drum. The grower, therefore, had to assume the further responsibility of cleaning, washing and chilling the shelled peas so that they could be safely held in bulk tanks of 10 - 12cwt capacity for anything up to 8 - 10hr. Hence the somewhat elaborate process incumbent on the farmer to install a dry cleaning drum to remove loose pods, stalk and haulm from shelled peas, then a pneumatic separator for finer cleaning, followed by a reel washer, and finally passing the peas through a fluidised bed chiller- freezer to bring down the temperature of the peas to about 2°C. In this way the grower can be a few hours ahead of the factory’s demands and provide a round the clock service with little or no fear of quality deterioration. At the point of filling the holding tanks, an automatic Avery scale is fitted, to register the exact weight discharged into the tanks, and this is the basis of payment for the crop to the grower by the processor, subject to a sliding scale taking into account the maturity of the peas, if applicable. Peas for dehydration must meet quality levels of maturity determined by a Tenderometer. This machine must be installed by both grower and processor. It is the last quality test at the grower's end and the first at the processor's. All peas for dehydration should fall into the category reading up to 100 on the Tenderometer scale. Any peas above that reading are normally rejected by the dehydrator, (and similarly by the commercial I 48 freezer processor) and are used for canning. A cross-check is made at the factory on arrival of the load. It is sometimes the practice to pay the grower a premium for peas at lower levels of tenderometer readings, say 90 maximum, to compensate for lower yields in the field. (b) Facto y Handling Dehydrated peas are regarded as a quality product, and anything less than a bright green pea which will reconstitute rapidly and hold its tenderness will rarely find a market outlet - therefore the cleaning process already carried out on the farm is almost repeated to ensure a first class product requiring the minimum of manual handling. Incoming tanks are emptied through a bottom gate into a gooseneck elevator with nylon perforated buckets that deliver the peas into a rotary cleaning/washing reel, thence to a pneumatic separator to remove any particles of stalk or skin left behind in the farm cleaning operation. The peas next pass through a flotation quality grader, whereby any over-mature peas are diverted to a separate processing line for catering quality packs. Any separation should be minimal, if quality control at the farm has been strictly observed. This fraction will need to be held over in chill conditions and put through the line at suitable intervals. After a visual inspection on a conveyor belt, to remove any discoloured peas, the product passes through a scarifier, which makes a shallow incision of 3mm in the outer membrane of each pea. This assists evaporation of the moisture during drying, and prevents the denaturation of the protein and case hardening of the skin. Without this process it is very difficult to achieve a good quality pea that will rehydrate quickly and have the level of tenderness required to compete with a frozen or canned pea. Scarifying will cause some leaching loss in the blancher but this can be minimized by the use of additives, such as sugar and salt, in the blancher liquor. The use of the latter was the subject of a Patent some years ago but the process is now universally available. Hot water blanching is preferred for peas, especially if the 'buffering' technique is used. The blancher must be heated with closed steam coils, open steam injection only being used to bring the blancher up to operating temperature. Buffering agents - sugar, salt, sodium carbonate, sodium sulphite - are made up in solution in two stainless jacketed pans fitted with electric stirrers. One is in use being pumped into the blancher whilst the second one is being prepared. The solution passes through a small pump, capacity 45-90 litres per minute, into the blancher water at a low level. Treated blanching water flows out from a top overflow pipe by gravity back into the make-up pan and the cycle continues, the additive levels being regularized by half hourly or hourly additions of dry additives into the pan in use. After 8 hours it is normal to change the blancher water completely as I49 it will have become very discoloured and sour smelling. Anhydrous sodium sulphite is used for sulphiting, to give a final residual level of 1250ppm in the dried pea. It may also be advantageous, especially where the water is hard to add sodium carbonate to sustain a pH of 9 to 9.5 in the blanching liquor. Sugar levels may be held at 1 to 1.5 percent, salt at 1 percent and sodium sulphite 1.2 percent. Addition of 0.5 percent of sodium carbonate may be necessary to arrive at a pH of 9. The blanching liquor temperature should be controlled at 97°C and the dwell time 1 to 1.5 minutes for peas with a Tenderometer reading of 100, reducing to 1 minute for younger, lower reading peas. Adequate blanching is testedat 30minuteintervalsbycheckingthat thereisanegativeperoxidase reading. A positive reading indicates that either blancher temperature or dwell time is too low. No cooling is necessary if the peas pass quickly to the dryer but it is essential to pass them over a dewatering screen. Drying and conditioning follow. The dry peas are then aspirated, to take out splits and skins. They are then screened for size, and sorted visually on 7m belts with metal detectors. Packing is normally in 25kg poly-lined paper (multi-layer) sacks, or poly-lined fibre drums. (4) Drying Conveyor Dryer scaled to desired output. Temperatures (input) through zones: 82"/76"/65 "C Conditioning; 50 "-52 "C Moisture down to 6 - 7% maximum Drying ratio: 5:l to 6:l according Tenderometer readings. Higher ratios are linked with low readings and highest quality. The product is highly sensitive to light after drying, and black pigmented polyethylene liners of 300 gauge and 5 ply extra strong quality paper bags are recommended for packing. ONIONS Onions represent some 50 percent of all dehydrated vegetables, excluding potatoes, used in one form or another in the United Kingdom, and this percentage is reflected in consumption figures for Europe and the United States. In America about half the Californian onion crop is contracted to the dehydrators, who handle some 100,000 tons per annum, yielding 10,OOO tons dry. This is supplemented by imports from Egypt and Mexico. In view of the importance, therefore, of onions in the production programme, the processing I50 data hereunder is supplemented with some horticultural data, in-plant storage methods and details of the varieties used in countries visited in recent years. (1) Flow Sheet Feed to line I Grading - (discard minus 50mm bulbs) I Loose skin removal (slat reel dry cleaner) I Washing (reel) I Topping - Tailing I Peeling I Inspection I Slicing I Inspection I Rinsing I Dewatering I Drying I Conditioning I Screening Kibbling to flakes I Inspection Inspection I Packing I Packing 151 (2)Varieties USA & Europe Southport White White Creole Primer0 Long- Day Short-Day Intermediate Globe Dehyso Dehydrator 3 F1 Hybrid Gilroy Dehydrator 14 Dehydrator 4 Dehydrator 6 Dehydrator 8 South Africa Sphinx Alba Egypt Fahoumy Guiza 6 Winter Nile India Bombay White Bulgaria Gorna Oryakhovitsa Romania Ranoresk Note: Long-Day varieties signify 14-15hr photo-period. Intermediate varieties signify 13 1 /2hr photo-period Short-day varieties signify 12-13hr photo-period (3) Horticulture It is of the utmost importance to know the day length and prevailing temperatures in the environment where the onions are to be grown. At ordinary temperatures in moderate climates, all bulbing onions require a certain day length to initiate bulbing. Late maturing varieties need longer hours of daylight to induce bulbing than those that mature early. Temperature also influences the amount of ‘bolting’, and this occurs more frequently with winter crops. It is essential, therefore, for the processor and grower to consult with the local Horticultural Institute or Research Station in the growing region to select suitable cultivars and to know the conditions under which they will give optimum results. Field trials are of the utmost importance to establish the parameters before a full scale dehydration operation is contemplated. White or brown skinned onions are preferred. Demand for red skinned onions is limited. (4) In-Plant Storage Onions may be delivered direct from the farms for immediate processing, or may be diverted into controlled temperature storage sheds to build up a reserve stock, so as to extend the period of processing. The storage facility is important where harvesting periods are limited by climatic constraints. I52 Windrowing onions mechanically. In the USA the regions where most of the onions contracted to processors are grown have a wide range of climatic conditions. Crops mature very early in the southern regions of Louisiana, Texas and Southern California, and mid-season to late season in areas north of the 36" parallel. This gives a longer processing season than most countries enjoy. Bulk storage of onions may be undertaken at the factory, or at an outside location if space is more cheaply available. The preference, however, is to locate the stores on the factory site to take advantage of the installed utilities, like electricity, heating, etc, and to have the benefit of centralised supervision. As a guide to the logistics of onion storage, the following details were noted from an actual installationof storageunits, each holding approximately 750 tonnes of onions. The method of delivery is in stillages, each holding 750kg, and the dimensions of these bulk boxes used for conveying the onions from the fields were 1.2m long by lm wide by 1.2m deep. They were fitted with perforated metal bases of heavy gauge and two strong wooden battens on the underside, so that when the stillages are stacked an air space is created to allow circulation of either warm or cold air. The onion store building was a pitched roofed shed 22m wide by 23m long by 5.5m high to the eves of the roof, designed to hold 720 stillages stacked 4 high in rows of 12 across the full width of the building. This lateral I53 row of 12 by4 stillagesis added to by a further 14 rows running longitudinally down the 23m length of the building, accounting for the full capacity of 12 by 4 by 15 stillages, or 720 in total. The first row of 4 stillages high docks into a plenum chamber, connected to 2 air fans, running the full width and height of the end wall. At each docking point there is a 'letter-box' aperture in the plenum which directs the flow of conditioning air through the space created by the battens. This flow is diverted upwards through the perforated bottom of the boxes and through the onions by fitting a block of timber in the air gap at the end of the longitudinal rows. This deflects the air upwards at any point where the baffle is fitted, even if the row is not completed to the front of the building. When the store is fully loaded the baffles will be at the end of the 15th row, allowing circulation along the full length of the store. Stillages are placed in position by forklift trucks, and each stack of four must be carefully located to ensure that there is an uninterrupted length of air flow gap as the rows are completed longitudinally. The temperature at which onions can be efficiently stored is extremely critical, and American tests published by Copley and Van Arsdel on Southport White Globe onions over four months storage periods at differing temperatures disclosed that the optimum yields of sound bulbs after this period of storage were obtained by utilising temperatures of 2°C (85 percent yield) and 30°C (79 percent yield). In designing and operating the store, therefore, it is vitally important to be aware of ambient temperatures at all times during the period of storage, and to judge whether a cool or warm air flow is to be used. This will vary according to whether the plant is operating in temperate, tropical or subtropical climates. It should be noted that, at temperatures of 10" to 20°C the quality of the bulbs deteriorates rapidly, yields falling from 49.9 percent at 10°C to 36.5 percent at 20°C. (5)Product Handling After feeding to the line, the onions are graded for size. Where labour is plentiful this is sometimes done manually, as the illustration of the Indian factory demonstrates. Bulbs measuring under 50mm in diameter are discarded, and in some instances are diverted to the fresh market. The quantity of this size of onion should be minimal, as the specification in the purchasing contract should clearly specify that bulbs must measure more than 50mm. The processing grades are 50 - 60mm upwards, and the reason for dividing into these grades is to accommodate an automatic topping and tailing installation, if such automation is desired. Where this method is used it is customary to feed up to two grades into I54 separate Autocore machines, each provided with a Shufflo feed. These units are supposed to handle 1000 to 1500kg per hour each, with two operators who are required to orientate the onions manually into cups on a metal conveyor, which presents the bulbs to a top-cutting and root-coring operation at a rate of 140 bulbs per minute. It must be stressed, however, that these machines are only efficient with full globe-type onions, and half-globe and flats are difficult to handle mechanically . Reference has been made in the chapter on preparation plant for onions to the Hydrout machines, which are manually fed but the processor is advised to investigate the safety factors involved in the operation of these machines. The peeling operation in most of the factories visited has been by abrasive machines, either batch or continuous. One of the major Californian dehydrators has indicated that American methods have changed in recent years, in that the onions having been cured in the field, are subjected to supplementary curing in the plant by applying an air blast of 35 o - 38 "C for the purpose of thoroughly drying out the skin, roots and tops, so that the bulbs can be mechanically cleaned as much as possible before coming in to contact with water. After this additional curing and on their way to the processing area, the onions pass through brushers, scrubbers and toppers. During this operation, skins, roots, tops and dirt clods are removed. Onions are then flumed into the plant and pass through various types of high pressure washer, the bulbs being conveyed on roller-type conveyors so that the high pressure water jets impinge on all surfaces. After drying, any remaining particles of skin are removed by efficient aspiration. Much of the specialised plant for scrubbing, washing and curing has been developed over the years by individual factories - they are not products of food machinery manufacturers. To revert to the more standard process, after grading, the onions pass through a dry cleaning reel with wide wooden slats in order to remove the outer skin and loose tops and soil, and are then washed in a standard washer reel. If an Autocore machine is not going to beused, topping and tailing must be done manually or by Hydrout (See Chapter 3 with reference to this machine). The onions are then peeled by abrasive peeler, preferably in a continuous model, although for small production a batch peeler may be used, provided it is a high efficiency machine. After peeling, the onions are inspected before being elevated to the slicing machines, which are set to produce a 4mm slice. A CC slicer with disposable knives may be used, or a more robust slicer, such as a modified cabbage slicer. If the latter type is used, it will be I55 essential to sharpen the knives every 8 hours, as indicated previously. The slicing process releases sucrose on the surface of the cut onion and it is necessary to give the slices a gentle rinse - usually by a water sparge pipe fitted over the elevator feed at the end of the inspection belt on which the slices have been inspected. The slices are dewatered before entering the dryer. Elevator feed to five pass dryer - onion dehydration plant, Nasik, India. (6) Drying Conveyor Band Dryer scaled to throughput for medium to large scale operation: 200kg per hour upwards of prepared material. Stove or Through flow Dryers for throughputs up to 1500kg per hour of prepared onions. Number of dryer units will depend on input required. Temperatures: Inputs through zones: 82°/ 76°/ 65°C 70°C first zone 50°C second zone 1 for Conveyor Band Dryers Tray Dryers - Stove or Through flow Conditioning: 50° to 52°C Dry to 6% moisture Overall ratio: 10.1 Drying down ratio: 6:1 to 6.5:l The drying down ratio represents the weight of fresh prepared onion in kg required to produce lkg of dried product. This is calculated by the formula: = Evaporative Factor 100 - End Moisture Raw Material Moisture - End Moisture = Water evaporated from lOOkg 100 Evaporative Factor of fresh material 100 - Evaporated water = Dry Material from 100kg fresh prepared. = Drying down ratio 100 Weight of Dry Material Example: Calculation of drying down ratio with onions containing 84 % moisture and drying to 6% end moisture is as under: 94 84 - 6 78 1.205 100 17 =1.205 (Evaporative factor) - 100 - 6 -= - loo =82.987kg Evaporation 100 - 83 = 17kg dry material = 5.88 Drying down ratio _. Note This figure is somewhat theoretical as there are some hidden losses in handling the raw material through all the wet processes, and losses of dry material between the discharge from the dryer and the point of packing off. These losses arise from 'fines' being emitted into the atmosphere by the air flow from the dryer fans, the conditioning bins, abrasion of product in sieving, handling and minor spillage. As part of the onion slices may be converted to kibbled onion or onion powder, there are further small losses in these operations. Taking these into account the drying down ratio for onions of the quality and total solids assumed in the example would be nearer to 6.0 to 6.5 : 1 but the formula provides a rule of thumb method for calculating a gross figure for drying down ratio. In practice, adjustments must be made for losses as identified above. (7)Kibbling and Powder Production Whilst onion slices are usually at a premium on world markets, it is inevitable that a percentage of dried slices will break down in handling, and it is usual to divert this material into a kibbling machine. This broken material will manifest itself when the slices are screened over a large gauge I57 sieve, and the 'through' material can then be kibbled down and screened out as 5mm or 7mm kibbled flakes (ie, sieve size). Onion powder is generally produced from fines created by sieving the primary product, and from undersized particles caused by kibbling. A Turbo Mill is strongly recommended for producing powder. The Baumeister mill has proved very efficient for this purpose, having a wide range of adaptability in output, fineness of particle size (no problem in grinding onions to minus 250 microns), and arrangement to suit the availability of floor space or geography of any factory. The mill must be housed in a separate room in the factory, sound insulated, and the cyclone vented air discharged to atmosphere. A typical installation to handle the powder production for a medium size plant would be a UT 12 model, powered by an 18 KW motor. The cyclone and supporting framework, including filter-bags require a height of approximately 5 metres in the designated building. Vegetable dust can create an explosion risk but the design of this mill has many safety factors built-in, which minimise this danger. (8) Packing Whilst most onions of overseas origin have been packed in poly-lined cartons, the American processors now use multi-ply bags hot melt sealed, as these are easier to handle than lined cartons. The use, generally, of the latter type of packing will depend on availability in the country of operation. Cartons and liners are normally available in most locations, and the specifications for these are as under: Cartons: constructed of double walled corrugated fibreboard with a minimum bursting strength of 17.5kg per sq cm. The carton should be constructed with the long flaps butting together. The flaps must be glued and taped, and the carton cross banded with nylon banding tape. A typical carton size for sliced or kibbled onions would be 60cm by 40cm by 30cm. The opening must be the 60cm by 40cm dimension. End opening cartons are not acceptable. Bulking is 83 cartons per tonne = 6.25~~ m at 12kg per carton. These should be 500 gauge low density polyethylene of sufficient size to twist at the neck and tie with twine. Metal or other closures should not be used, nor should the liners be heat sealed, as this method tends to entrap air in the pack. Two liners filled with product are accommodated in each carton. Liners: Dehumidification: It must be stressed again that the packing area should be dehumidified and cooled, especially in tropical areas, to avoid entrapping I58 hot humid air in the polyethylene liners. Relative humidity should be reduced to 25 - 30 percent and the product temperature should be no higher than 12°C. These conditions should also apply in the milling area. Powder Packaging: Onion powder should be packed in metal-topped drums containing 25kg. As onion powder is very hygroscopic, it is necessary to nitrogen-flush wherever possible, or failing this to incorporate up to 2 per cent of anticaking additive. Cultivation Guide Lines for Onions (1) Sow either in nursery beds or direct by precision drill: Seed approximately 6.6kg per Ha. Twin lOcm rows by 46cm centres (planted from nursery beds lOcm apart.) Plants per row: 19.7 per metre. Density: 66 plants per square metre. Plant population 661,000 per Ha. (2) Fertil: .sers Organic: 2000kg / Ha. Sulphate Ammonia: lOOkg/Ha. Phosphates: 15Okg/Ha. Potash: 75kg/Ha The above will be subject to soil analysis and requirements. (3) Herbicides and Pesticides. Post-emergence application: Linurin or Aflon - 4.2 litres per Ha. Apply Calomel Dust against onion fly. Benlate or Dithane against botrytis. (4) Irrigation Total precipitation in growing period: 80cm. 70 days irrigation at 5-6 day intervals. (5) Maturity After lifting, bulbs should be cured in rows on the field until the tops wither. Size of bulbs for processing should be from 60mm upwards. PARSNIPS (1) Flow sheet Feed to line I Dry Cleaning I Destoner Washer I Steam Peeling I I59 Skin Removal I Inspection I Dicing I Blanching I Sulp hiting I Dewatering I Drying I Conditioning I Screening I Inspection I Packing (2) Varieties Any smooth white skinned variety resistant to canker, short root-type preferred. (3) Product Handling The parsnips are fed into the line from a bulk feeder, having been well trimmed at the farm and topped at the shoulder. Next they pass into a dry cleaning reel to take off excess soil, etc, then toa destoner-washer.They are steam peeled and the skinremoved. Inspection follows and here it is important for the operators to look for any incidence of canker, large roots should be sliced in half, so that any trace of canker can be seen. Such roots must be discarded. Theparsnipsare thendiced inaGDicer,eitherasl0mmxlOmmxlOmm cubes or 1OmmxlOn-tmx2mm flakes. Blanching can be either in hot water or in steam. SO, is metered into the blancher from a make-up pan if a hot water blanch is used, or, if steam blanched, the dice are passed through a sulphite applicator tank, supplied by the make-up pan. The product is then dewatered. Blanching is for 3 minutes, or as long as necessary to produce a negative peroxidase test. Drying is by conveyor dryer, followed by bin conditioning. The dice are elevated to a screen for grading, with a 6mm sieve to take I60 out small particles and fines. Inspection is camed out on conveyor belts fitted with metal detectors. Packing is in 25kg multi-ply paper sacks with 300 gauge polyethylene liners. Conveyor dryer scaled to throughput. Inlet temperature 93'C reducing to 87' and 70°C in the last stage. Dry down to 12% in the conveyor dryer and condition to 7% in bins. Raw moisture = 83% Overall ratio = 9:l to 11 :1 Drying ratio: 6:l PARSLEY, SAGE and LEAF HERBS (1) Flow Sheet (4) Drying Feed to line I Reel Dry Cleaning I Triple Washing I Inspection I Drying I Cutting (Stalk separation first stage) 1 Inspection I Aspiration I Screening - Milling I Packing (2) Varieties Parsley - Moss Curled Sage - Broad-Leaved Thyme - Broad-Leaved (3) Product Handling Herbs are fed into the line 'on-stalk' and passed through a dry cleaning reel to remove dirt and extraneous matter. They are then triple washed in a flood washer with three tanks, or passed through two double tanks in line. Herbs are examined on a wide conveyor belt where the operators remove 161 any yellowed leaves or debris. Herbs then pass into the dryer, usually a conveyor, single-pass unit with three heat zones, and drying is usually completed in a 45-60 minutes cycle. Cutting into granules or flakes takes place after drying, and a standard method is to hand-feed stalk-first into a J type cutter and, if the discharge chute is removed, the flaked leaves tend to separate from the stalk, which shoots out beyond the leaf. This is effective with parsley but other herbs may need to be separated from the stalk by aspiration. The flake or granule size will be determined by market requirements and can be regulated by the knife spacing on the cutter. After inspection, the dried leaves pass into a Sortex air separator which finishesanyremovalofcomminuted stalkleftbehindby themechanical separation in the cutting operation. The material is then size graded by a screen and packed. Mixed stalk and leaf may be milled for powder, if there is a demand. As thedryingcycle is short, a single-pass dryer is preferred,scaled to desired throughput. Alternatively stove dryers may be used. Raw moisture of parsley is 84435% and it is particularly important to retain the fresh green colour in the dried product, hence the necessity to keep temperatures fairly low, 80'/ 70"/ 65°C through the zones. Dry to 5% Overall ratio = 121 Drying ratio = 71 SPINACH 1) Flow Sheet (4) Drying Feed to line I Precleaning I Washing (triple) I Inspection I Cutting I Blanching I Sulphiting I I62 Dewatering I Drying I Conditioning I Aspiration I Screening I Inspection I Packing (2) Varieties. Winter Prickly - Medania Summer Spinach. (or indigenous varieties) (3) Product Handling. Spinach is usually cut by hand on the farm and delivered to the factory in crates or field boxes. These must not be allowed to stand for any length of time, and should be loaded lightly into a bulk hopper allowing air to circulate freely. Precleaning is done by hand and consists of removing crowns, large stalks, wilted leaves, weeds, etc. Extremely efficient washing is required, hence the need for a triple washer. This hasthree sections,each with a good flow ofwater that isaerated by compressed air. A good flow of fresh water is needed in the last section and any overflow can be pumped back into the second section. If any grit remains after triple washing, the spinach may be put through a final reel washer, or alternatively held in tanks with a through-flow of fresh water, before feeding into the triple flood washer. This will release some of the soil or grit and ease the washing process in the threecompartment flood washer. A further inspection is made to reject any blemished leaves or extraneous matter, before cutting. This can be done on a J dicer, hand fed, and it is usual to cut strips by removing the cross cut knife spindle. Feed fingers are used between the circular knives to ensure positive transfer of the leaf. Blanching should be in flowing steam for 3 - 4 minutes at 95°C. The product is then sulphited by a dip in a sulphite applicator tank. Dewateringisveryessentialas thereisa lot ofsurfacewateron theleaf. If this cannot be removed by a reciprocating screen dewaterer, then the leaf strips will need to be centrifuged in batches. This will ease the initial drying I63 problem. Drying is by conveyor dryer scaled to throughput. Conditioning in bins. The dried strips are fed into a Sortex air separator to remove any unwanted heavy stalk. If required, the product can be screened to take out fines but possibly the aspiration will have been adequate. Inspection over belts with metal detectors. Packing in multi-ply paper sacks with 300 gauge polyethylene liners. (4) Drying. Inlet temperatures: 82"/ 74"/ 65°C dry to 7% Conditioning: 50°C dry to 5% Raw Moisture: 94% Overall ratio: 17.1 - 19-1 Drying ratio: 13:l SWEDES - White Turnips 1) Flow-Sheet Feed to Line I Dry Cleaning I Destoner-Washer I Steam Peeling I Skin Removal I Inspection I Quartering I Dicing I Blanching I Sulphiting I Dewatering I Drying I I64 Conditioning I Screening I Inspection I Packing (2) Varieties: Swedes White Turnips Purple Top - Green Top Early Snowball - Green Top White (3) Product Handling The swedes, which ideally should be not in excess of 13cm in diameter, are fed into the line from a bulk feeder. It is essential the roots be well trimmed on the farm, with tops cut off and the root trimmed well back to the butt. They are fed into a dry cleaning reel to remove any soil or extraneous matter, then transferred to a destoner-washer before steam peeling. The peel is removed by a skineliminator, and the swedes inspected and trimmed where necessary. If the swedes are in excess of 13cm diameter it is advisable to quarter them on the inspectionconveyor. This willdisclose whether any are infected withroot canker, to which swedesaresometimes prone. The main reason for quartering large swedes, however, is to reduce them to a suitable size for feeding into the dicer. The roots, either whole or quartered are elevated into a G type dicer, set for 9.5mmx9.5mmx9.5mm dice or 9.5mmx9.5mmx2mm flakes. Occasionally swedes are cut to flakes 20mmx20mmx2mm. The G dicer has acapacityof6000kg perhourof9.5mmdiccbuta lesser throughout on flakes. The knives require changing every 8 hours and should be honed and sharpened. This applies to all root vegetables. Blanching is either in hot water at 99°C for 3-4 minutes, or in flowing steam. If a water blanch is used the sulphite is metered in from a make-up tank, along with other additives to inhibit leaching losscs (sugar and salt). If steam blanched, the sulphite solution may be sprayed on, or the dice can pass through a sulphite dip tank. Steam blanching will require a dwell time of 5 minutes, or until such time as a negative peroxidase result is achieved. The sulphur dioxide level in the end product is 1000ppm. After dewatering, the dice or flakes pass into the dryer, thence to the conditioning bins, and screening is through a 6mm sieve toremove fines and small particles. Packing is usually in 25kg multi-ply paper sacks with 300 gauge I65 polyethylene liners. White Turnips are processed in exactly the same way. (4) Drying. Conveyor band dryer scaled to throughput. Temperatures (inlets): 110"/ 95"/ 85°C Conditioning to 7% in bins: 52"/ 54°C. Raw Moisture: 89 - 91 % Overall ratio: 12:l to 14:l Drying ratio: 9:l Dehydrated swede should be bright yellow. Any tendency to 'browning' indicates temperatures too high in the second and third dryer zones. Turnips should be creamy white and free from browning and blemish. TOMATO SLICESFLAKES. (1) Flow Sheet. Feed to line I Washing-Sorting I Removing Calyx I Washing I Slicing I Inspection I Dewatering I Drying I Conditioning I Kibbling I Screening I Inspection I Packing I66 (2) Varieties. (3) Product Handling. The tomatoes are discharged from field boxes, or bulk, into a bulk feed hopper.Theyare thenelevated intoa tomato washer integrated witharoller- type inspection conveyor, where damaged or unsuitable fruit are removed. This process is followed by a second inspection conveyor with three channels on which the operators remove the calyx and the fibrous top of the core. The latter operation can be done mechanically, if throughput warrants the installation of a battery of manually fed Hydrout corers. This is a similar machine to that used for onion coring but in some countries they are not permitted under factory safety regulations. A secondary washing follows in a flood-type washer, and then the prepared tomatoes are fed into a CC slicer set to cut 4mm slices. After a further inspection, the slices are dewatered and placed on the drying trays of a double or single tray dryer. During the transfer from the 'hot' zone to the 'cool', the slices must be turned on the tray to prevent adhesion to the mesh and to expedite drying. The slices are then transferred to bins for conditioning down to 5 percent. The reason fordrying down to5 percent is that the tomato is very hygroscopic and can pickup moisture if there is any delay in final processing, ie, kibbling, screening and inspection. Tomato slices are rarely sold as such, and invariably are converted to flakes by kibbling in a suitable machine. Flaking by roller drying is rarely practised nowadays, as the resulting colour is poor owing to the high drum temperatures, and the particle size is nearer to a coarse powder, which even after sieving is much inferior to spray dried tomato powder made from tomato concentrate. The kibbled material is fed on to a vibratory screen to eliminate fines, then inspected and packed. To avoid too much breakage of thc flakes, they are packed either in poly-lined cartons or fibre-board drums. Cal J - PeteMech - Roma (all oblate types - USA seed) (4) Drying. Tomato slices can only be dried on trays, owing to the necessity of turning or riffling the product halfway through the drying cycle. This is not really feasible on a conveyor dryer. The trays must be waxed regularly to prevent product adhesion. The total drying cycle, excluding conditioning will be 4 - 5hr and temperatures will range from 80°C in the hot zone to 60'C in the cool zone. Conditioning is at 50" - 52°C to 5% Raw moisture = 94-95% I67 Overall ratio: 201 to 221 Drying ratio: 161 to 17:l Cultivation Guide Lines for Tomatoes (1) Sowing Direct: 890g per Ha. Nursery Beds: 190g per Ha. This method is recommended in tropical climates. All seed should be dressed with fungicide and stored at 4'C until used. Spacing 45cm apart in l00cm rows. (2) Fertilisers Farmyard or other organic manures are desirable, applied at the rate of 6 tonnes to 12 tonnes per Ha. Apply 500kg per Ha of 12:12:17+2 at planting. Supplement 250kg per Ha. of Sulphite of Ammonia after fruit has set. (3) Herbicides Dynid: Metrobromuron: Dachtal50 percent WP. (4) Pesticides Dimethoate: (against midges) Endosulphan against Leaf miners. (5) Disease Control Koccide 101: Cobox: Cuprovit; alternates with Dithane N45 or Antrocol for bacterial spot, mosaic virus, stephylium and blossom end rot. Flower drop can be controlled by a fine mist of water when the fruit sets. (6) Maturity Picking must be at regular intervals when full colour is achieved. Avoid bruising. Harvesting 12 - 14 weeks after planting. Plant population: 25,000 - 30,000 plants per Ha., according to variety. Yield anticipated 40-50 tonnes per Ha. I68