Carob, Ceratonia siliqua is also called Saint-John's-bread or locust bean.
It grows to about 15 m (50 ft) in height and has dark, evergreen, pinnate leaves. The small, red flowers have no petals. The fruit is a brown, leathery pod about 10 to 30 cm (4 to 12 in) long and contains a syrupy to biscuity flesh of an agreeable sweet taste, in which lie a number of seeds. The pods are edible and are often used for livestock feed. The seeds, which are remarkably uniform in size and weight, are thought to have been the original standard carat weight used by jewellers and goldsmiths.
With their deep root system and specially adapted leaf surfaces Sweet Carobs are adapted to dry conditions, saline water and intense heat. They complement other shrubs and trees which can be included in farming systems for dry areas such as saltbush, olives and honey locusts as well as bush tucker, timber and woodlot species. Carobs are also fire resistant and provide green pick and shelter for livestock.
A mature female Carob tree can produce up to 100 kilos of beans, each pod containing roughly the energy of a Mars Bar. That's 300,000 Mars Bars per hectare! Apart from the stock feed value of the beans, the health food market currently pays between $1.50 and $3.00 per kilo for carob.
The tree is a perennial leguminous tree native to the Mediterranean basin and south-west Asia. It has been cultivated for over 4,000 years. It grows productively to an altitude of 1215 m, with a life span of more than 100 years. It is tolerant of moderately high salinity levels (ACIL 1984). World carob pod production is approximately 320,000 tonnes year (Tous et al. 1996).
The carob fruit, typically produced on female and hermaphrodite trees older than 6 years, is valued for a range of products derived from the seed and the pod. From the seeds, the endosperm is extracted for a galactomannan, which forms an edible gum (termed 'carob bean gum' or 'locust bean gum', LBG) and has become a valuable natural food additive. Carob powder, made by grinding the roasted pod, is used for the human food industry (with cocoa products and syrups). Ripe pods also have potential as a high energy stock feed. The gum is used extensively in Australia as an thickening or binding agent, particularly for canned pet food products. A study undertaken by Race, Curtis and Booth (RIRDC 1998) reveals that current imports valued at AU$10million/year. The current Australian demand for 'pet food' and 'technical' grade gum is estimated at 1200 tonnes/year, with a further 200 tonnes/year of the higher quality 'food' grade gum. Assuming a modern plant was built in Australia, the current Australian demand for carob gum could be met with approximately 2250 tonnes of carob seed (seed value at $ l600/tonne). This equates to 5405 ha of trees (at 104 trees/ha) with medium rainfall and low technology management (yielding 40 kg tree); or 1080 ha of trees (at 208 trees/ha) with supplementary irrigation and fertilising (yielding 100 kg/tree). As such, carob could be a commercial tree crop for landholders in the Murray Valley region. This could be through the sale of seeds and pods, or as a supplement to livestock feeding. Improved Sweet Carob cultivars are being grown successfully in young plantings at the Loxton Research Centre, Gawler and Burra and there is a processing plant at Burra currently paying up to $800/tonne for raw pods.
In Races study economic analyses were undertaken to assess the relative viability of commercial returns when trees had access to adequate water through medium rainfall or irrigation, and growers had access to both the carob gum and powder markets. Commercial opportunities for carob growers within Australia vary considerably depending on establishment and maintenance costs, yields and access to markets.
Carob has been intermittently explored over the last 20 years as a potential tree crop industry in low rainfall areas of Australia (<500 mm rainfall/year).
Farm experience indicates carob trees are suited to the marginally productive agricultural land in the Murray Valley. Carob has an extensive tap root system that can grow to depths of 20 m, enabling production with just 250 mm rainfall/year. However, conditions for commercially viable yields appear to require at least 500 mm or supplementation from irrigation or access to a moderately shallow aquifer. Carob begins to produce a commercial yield after approximately 10 years.
The importance of investigating the potential of a carob agroforestry industry has been heightened by the limited options for low rainfall agroforestry, the need to improve management of low rainfall areas in the Murray-Darling Basin and the need to find a way to exploit the perched water tables associated with current land-use systems. A viable carob industry would improve low rainfall agricultural productivity (shelter and fodder) and diversify farm incomes, assist in the management of land and water degradation, particularly help in the control of salinity problems, allow reuse of domestic, industrial and horticultural waste water for its irrigation, and contribute to regional industry development and import replacement. Carobs regenerate after burning and in Spain, are frequently grown close to villages because they can slow down the path of a grass fire so they represent a valuable element for use in the design of properties with flamable species such as olives, cereal crops etc.
Carob processing in key regional locations could contribute to regional employment and so enhance the viability of rural communities. A viable carob industry could contribute to LBG import replacement (estimated at AU$10 million/year) and have the potential to compete in a world LBG market worth AU$ 100 million/year.
ACIL Aust Ltd (1984) Agroforestry in Victoria - Appraisal of Viable Systems
Tous J (1994) Carobs a worldwide perspective, Proceedings of Symposium on Olives and Carobs for landcare and for profit University of Adelaide - Roseworthy SA