Carob

24.05.17

Native to the Mediterranean region, the carob (Ceratonia siliqua) is a flowering evergreen tree cultivated mainly for its edible pods and seeds, but also grown as an ornamental garden specimen. Commonly known as St John’s bread or locust bean, it is a member of the legume family, although it does not fix atmospheric nitrogen.

Carob trees can live for over 100 years, grow to 15m and produce a trunk girth of up to 3.5m. The leathery leaves grow in four to five pairs of oval-shaped leaflets; new growth is bronze coloured and mature leaves are dark green on the upper surface and light green to grey underneath. The trees can be male, female or hermaphrodite (both sexes).

Overview

The small flowers are 4-5cm long, greenish-yellow to red and have no petals. The female flowers develop into pods resembling green broad beans and become a glossy dark brown colour with maturity. Measuring 10–25cm and weighing 20–40 grams, each pod contains sweet, chocolate-flavoured pulp and up to 15 seeds. Similar in size to a watermelon seed, carob seeds are hard and brown in colour.

Whole carob pods are used unprocessed as stock feed or coarsely ground (“kibbled”) to separate the seed and pulp. The seed is usually sold to be processed into gum and used in the food, pharmaceutical, cosmetic and pet food industries; or it is used in the manufacture of inks, paints, ceramics, paper and chewing gum. The kibbled pulp is used as stock feed, sold as is to the food industry or processed (raw or roasted) into powder or syrup. High in nutritional value and flavour, carob powder or syrup is a natural sweetener and a caffeine-free cocoa substitute, used in a range of food products including confectionery, syrups, pastes and desserts.

Carobs have been grown in Australia since settlers were encouraged to plant seeds in the 1890s. As in the Mediterranean region, the tree was valued for shade, windbreaks, shelter, food, fodder and beautification. Despite the early success of plantings, Australia’s first commercial carob orchards were not established until the early 1980s. Plantings have steadily increased since due to new industry developments, including the availability of grafted cultivars, technical information, the ability to harvest mechanically and the opportunity to sell raw pods to Australian processors for milling and on-selling of seed.

Carob production is a small but growing industry, and the interests of growers are represented by Carobs Australia Inc.

Facts and figures

Carob trees are best grown in conditions similar to the Mediterranean climate and alkaline soils from which they originate, and are tolerant of drought, salinity and frost
The Australian carob industry has been evolving since the early 1980s, with the export industry only established in 2014, production levels are low compared with other participants in the world market
Carob trees, seeds and pods, have a multitude of uses, spanning dozens of industries
A slow growing crop, carob trees can take up to 10 years to reach full commercial production levels

Production status

While carob is grown in six states and territories of Australia, the key production regions are western New South Wales, southern South Australia and the northern agricultural region of Western Australia. New plantings are in western areas of New South Wales, Queensland and Victoria, and in the agricultural areas of South Australia and Western Australia.

The growing area is about 400ha, mainly located in the states of South Australia (34%), and Western Australia (20%). In the other states there are an estimated 30,000 seedling carobs within and adjacent to fenced grazing areas for sheep and cattle.

Map of current and potential growing regions

Uses

Overseas, carob seeds are used as a cash crop, while the discarded pods are fodder for pigs and other animals. The carob seeds are 35% gum (locust bean gum or ceratonia), which is processed and used as a gelling agent, stabiliser or emulsifier in ice-cream, yoghurts, dessert fruit filling and salads. It is also a component used in thickeners and to prevent sugar crystallisation in confectionery.

Products manufactured using the ground carob seed gum include inks, paints, textiles, oil well drilling additives, explosives, ceramics, paper, adhesives, chewing gum, pet foods and cosmetics. Oil extracted from the seeds (algaroba) is used in the pharmaceutical industry.

Carob is valued for medicinal purposes due to its high pectin and tannin contents, which are both useful for digestive ailments. The oil also contains lignans, which have many benefits including antiviral, antifungal, antibacterial and anti-inflammatory qualities.

The pods, which can have a sugar content of up to 50%, can be eaten fresh when they are young and green, however they are more often harvested when mature and dark, then dried and kibbled (coarsely ground) to separate the seed from the pulp. The kibble, which is high in calcium, fibre and natural sugar, is sometimes sold as a healthy snack food or in products like trail mix, and can be used as high-energy stock feed (containing 21% protein).

The kibble may be milled or ground and sieved to produce caffeine-free carob powder, which is a natural sweetener used as a healthy substitute for cocoa powder in baking and food manufacture, as a food stabiliser, or a darkening agent. It is also used to make molasses and alcohol, and as a substitute for coffee.

Carob pods on the tree are used as supplementary stock feed for grazing stock (cattle, sheep, goats and donkeys), particularly when trees are planted in windbreaks along the edge of the paddock. The tough bark is resistant to ring-barking by grazing stock. Although carob is not a nitrogen fixing species it is quite deep rooted, and tolerates considerable drought.

Carob trees are often used in landscaping for street planting, privacy screens and as an ornamental shade tree; as well as on farms to provide windbreaks around homesteads, orchards and paddocks. The tree is fire resistant and able to regenerate after burning. In Spain carob trees were planted near villages to slow down the pace of grass fires.

A minor carob product is the moderately dense wood (carouge), which is used as a specialty furniture timber and in some cases as firewood.

Production Requirements

Growing regions

Grown in all five states and the Northern Territory, the biggest carob orchards are in western New South Wales, southern South Australia and the northern agricultural region of Western Australia. Newer plantings are largely in the western areas of New South Wales, Queensland and Victoria, and in the agricultural areas of South Australia and Western Australia. These regions have a similar climate to the Mediterranean region where the carob originated.

Soil type

Carob trees grow best in high pH limestone and other alkaline soil types with good subsurface drainage, including on a variety of well-drained and well-aerated soils, including sands and clay loams. Carobs also do well on rocky dry sites where their tap root can penetrate to reach water. They will not tolerate heavy clay and waterlogging is likely to induce stunting or death.

Carobs prefer a soil pH_(water) level between 6.2 and 8.6, and are known to tolerate slightly saline conditions.

Climate

The carob tree is best suited to temperate and semiarid regions of Australia, similar to the Mediterranean region, but it can also grow well in subtropical areas. The tree flowers in autumn, and the pods develop through winter, spring and summer, and ripen for harvest in late summer. In order to achieve maximum sugar content before harvest, hot dry weather during the late summer and autumn ripening period is critical.

Carob trees are suited to regions of 250–600mm of annual rainfall but 500mm is considered ideal. Carobs are drought resistant and have an extensive tap root system that can develop 20m deep in the soil. Carobs grow well in arid areas with artesian water supplies and respond well to supplemental irrigation. Low rainfall in summer reduces the risk of fungal attack as the pods reach maturity, which results in sugar fermentation.

Carob trees thrive in hot summers and can withstand maximum temperatures up to 50°C with a relative humidity of 6%. They do not tolerate severe frosts but are less frost sensitive than citrus (as a potential environmental indicator). Temperatures under -4°C can kill or injure young trees by damaging their buds and small branches. Winter temperatures below -8°C will damage the mature plant and retard fruiting.

While carob can be found growing in warm, coastal environments, trees in these areas do not have regular winter dormancy, making propagation by budding and grafting difficult, as well as affecting yield.

Varieties

The development of carob varieties is limited globally, however preliminary breeding is occurring in Spain to improve agronomic and processing qualities, such as size, yield and sugar content of the beans, and also the size, hardiness and maturation rate of the tree.

A number of varieties are cultivated and available in Australia, including 11 of the best European and American selections that were brought to Australia in the early 1980s. Successful Australian-bred varieties include Irlam and Waite, while others (originating from Cyprus, Tunisia, Mexico and Spain) include Tylliria, Sfax, Casuda, Badan and Cypriot. Also available in Australia are Clifford, Santa-Fe, Laguna, Molino, Tantillo, Bath, Maitland and Amele.

Planting and crop management

Carobs seeds or seedlings are planted in spring in full sun, with carob seeds germinating best at a soil temperature of 22–26°C. Polythene socks or ‘growtubes’ can accelerate the growth of seedlings. Grafted trees are not yet readily available in Australia and will speed up the orchard establishment time, as carob is a very slow-maturing crop, taking 6–7 years before bearing fruit. A suggested spacing of 10x10m (100 trees/ha) allows for orchard maintenance and maturation space for each plant.

Pollination can be maximised by planting one hermaphrodite tree (e.g. Clifford or Santa Fe) for every eight females, or grafting male or hermaphrodite scionwood onto female trees. Hermaphrodites have a longer flowering period than males.

Slow release fertilisers or manures applied at planting will provide adequate nutrition for seedlings. Application of nitrogen, phosphorus and zinc may be beneficial to mature trees, however individual tree requirements should be monitored through leaf tissue analysis, and fertiliser rates should be tailored to individual sites. In Spain, leguminous annual crops are frequently grown between carob trees, and up 3–4 tonnes of manure per hectare are applied every 3–4 years.

Pruning is required to control suckers during the early stages of growth, and again later when branches are damaged or become overcrowded. Irrigation can boost production when rainfall is inadequate for commercial orchards. Further information on planting and crop management is provided in Carob Agroforestry in the low rainfall Murray Valley, and the website of Carobs Australia Inc.

Weeds, pests, and diseases

There are no major pests and diseases of carob in Australia, other than the carob moth, which has become a major pest of carobs in both Western Australia and South Australia. Carob moth attacks a range of hosts, including acacia, and fruit and nut trees. Removal and destruction of larvae infested pods from the carob trees is important and organic insecticides can be applied to kill the larvae.

Routine spray schedules can prevent build-up however there are no pesticides registered specifically for carob moth. Affected pods can be heat treated and put into insect-proof or cold storage. Moth traps, lures and mating disruption techniques can be installed to control the adult moths. More information is provided in the Western Australia Department of Agriculture and Food’s fact sheet Carob Moth, and by contacting their offices.

A potential pest of carobs is citrus red scale, which is controlled by the Aphytis wasp. The Rutherglen bug has been reported to destroy seedlings in Western Australia through defoliation, so close monitoring of establishing seedlings is necessary in regions where the bug exists. Fungi will attack carob seed and seedlings, however establishing orchards with grafted stock will eliminate this issue.

Grazing animals are a pest for seedlings and should be excluded from young orchards. Rodents may attack stored pods and kibble, which should be kept in rodent proof storage facilities.

Despite potential threats, Australia’s largest and most successful grower and exporter of carob uses no insecticides or pesticides, and has achieved organic certification.

Infrastructure Requirements

Cultivation of carob trees requires standard equipment for orchard establishment and maintenance such as:

tractor
auger
mower or slasher
sprayer
pruning equipment
drip irrigation system — ideally with variable flow drippers
fencing to keep grazing animals away from young plant

hand-harvesting equipment — poles, ladders and collection buckets or tubs
mechanical harvesting equipment — an adapted almond harvester
aeration tables for drying the harvested pods, assembled using nets and poles
an insulated rodent-proof shed if storage is required
if processing, washing facilities and a carob kibbler, mill and roaster.

Harvesting & Processing

Carob pods are harvested using mechanical harvesters or by knocking dried pods from the trees before gathering them from the ground by hand. Ripe carob pods are harvested in March–April, then stockpiled and dried until the moisture content reduces to 10% or less. The dried pods are washed and then kibbled to separate the pulp from the seeds. Alternatively, they can be boiled until tender enough to cut them open and remove the seeds – but this is labour intensive and would only be done on a very small scale. Dried pods are then cut into small pieces and dried out well, before being processed.

Value-adding by the farmer can be achieved most successfully through the purchase of processing equipment, including a carob kibbler, mill and roaster, however the outlay must be proportional to the volume of harvest to make it profitable (and maybe take advantage of the opportunity to provide processing services to other producers). Value adding can also be achieved through the manufacture of a wide variety of food products such as baked goods, confectionery, syrup, pastes and marinades.

Packaged whole pods, both fresh and dried, are sold for human consumption; however sales of this product in Australia are limited, and the few sales were mainly in farmers markets.

Markets & Marketing

The largest producer and exporter of carob is Spain, followed by Italy, Portugal, Morocco, Greece, Cyprus and Turkey. In 2014, a South Australian company started exporting carob to Europe, India, Indonesia and Thailand. This is Australia’s largest producer and only exporter, producing 100 tonnes per year, with the capacity to expand to 600 tonnes.

The company’s product has been described by the food industry as having superior flavour and quality compared with imported product, which has been attributed to the selection and utilisation of high yielding cultivars and use of modern processing equipment & procedures.

The potential for other producers to start exporting will be realised as established crops mature and more processing plants are developed on farm.

Risks & Regulations

Risks/challenges

Carob trees are very slow-growing, taking 6–7 years to bear fruit and approximately 10 years to produce a commercial harvest. They can also bear light and heavy crops in alternate years, making yield and income more variable from year to year, compared with other agricultural enterprises.

Other challenges faced by the industry in Australia are a lack of detailed biotechnology and economic data, and limited linkages between research and industry. There is a lack of market intelligence as there has been little research into what is needed to establish the critical mass for a viable regional industry.

Regulatory considerations

The regulatory considerations that apply to all Australian farms, including laws applying to chemical use and management, occupational health and safety and transport (including machinery movements and the loading/unloading of harvested product), also apply to carob production operations. If pods are being processed on farm, local government should be consulted to ensure that prospective facilities and operations meet local planning and environmental regulations.

Before buying new land to plant orchards, a thorough investigation of the land’s suitability for a horticultural enterprise and its cropping or land use history should be undertaken. This may include identifying a history of chemical contamination (and residue levels) as some export licences may be withheld on products grown on land where chemical residues exist. Potential disease risks should also be investigated.

Some disease pathogens can survive in the soil for many years, so information about previous disease outbreaks will assist determining which trees are suitable for planting. This information can generally be obtained from the relevant state planning authority. Growers are also responsible for regularly inspecting their orchards for notifiable pests and diseases and reporting any incidence to the relevant state agriculture department.

When planting new orchards and establishing additional on-farm infrastructure or access roads, liaison with the state government agencies responsible for planning, native vegetation laws and water licences will be necessary. Some land use applications will also need to be considered by the relevant local government authority.

Land ownership in itself does not provide owners the right to clear native vegetation for orchard establishment, therefore an approval or a licence to clear land will be required from the relevant state department of agriculture, environment or planning. Failure to have the relevant approvals may result in prosecution.

When processing raw product for value adding, consideration must be given to food standards regulations, as administered by Food Standards Australia New Zealand and set out in Chapter 3 of its Food Standards Code. Information about certification can be found at, but is not limited to, the websites of Freshcare and HACCP.

Publications

Publications/information
Carob Agroforestry in the low rainfall Murray Valley RIRDC report (1998)

The Carob The Archives of The Rare Fruit Council of Australia factsheet (1988)

Carob Beans – The Food Forest website fact sheet (2015)

Carob Moth – Department of Agriculture and Food WA factsheet (Oct 2014)

Esbenshade, H., & Wilson. (1986) Growing Carobs in Australia. Goddard & Dobson, Melbourne– out of print; however, available from all State Libraries

Batlle, I., & Tous, J. (1997) Carob Tree Ceratonia siliqua L.. Institute of Plant Genetics and Crop Plant Research, Gatersleben/International Plant Genetic Resources Institute, Rome, Italy.