General Overview of Carobs in Australia
The history of carob cultivation in the world, the uses and processing of carob products, and a description of growing practices in Australia.
I grow carob trees just outside York. My orchard is about 3,500 trees which have been in the ground between 2 to 10 years. Some have been grafted.
My information has been collected from many sources, books, research papers, conference notes and anecdotal evidence over the past 4000 years. The latest work is a compilation of all the research that has been done and recorded since the 1950s. Dr. Tous has put it in a book. Dr. Tous actually works in a research institute in Spain that has quite a large genetic bank, gene pool of carob trees. They do lots of experimenting with it.
I will start off with a little about the history of the tree. It has been cultivated since ancient times in the Mediterranean, which is where it began. The exact origin of the species is unknown. A lot of people have ideas about it, but they don't agree as to where it originally came from. It was generally placed around the eastern end of the Mediterranean, around Palestine and along the south coast of Turkey and down into the southern Arabian peninsula.
The ancients used to substitute tree crops for grain crops in areas that were too steep and rocky for normal grain cultivation. That is generally why the olive and the carob became domesticated. It has long been recognised as a substitute for grains in times of drought and famine. The period when carob was cultivated remains obscure, but archaeological evidence suggests that the Egyptians may have been some of the first farmers to cultivate the tree. They have found pods in old sarcopagi from tombs dating about 1900 BC. They have also been found in archaeological digs in Israel. Some charcoaled remains of seeds were dated to the end of 4000 BC. So, it has been used for quite some time.
It wasn't mentioned in the Old Testament, but there are two mentions in the New Testament. The first one is mentioned by St. John the Baptist. He said that while he was in the wilderness he consumed the locust and the wild honey. The locust that he was eating was not grasshoppers, but was believed to be carob pods, so he was living on carobs and wild honey. The other mention was that of the prodigal son, who, it was said, would feign to fill his belly with the husks that the swine did eat. These husks that the swine ate, again, were carob pods.
Carob was spread to Italy by the Greeks during their great reign of the world. And the Arabs regarded carob more highly than the Greeks and Romans and spread it a lot further. They spread it right through north Africa and into Spain.
The seeds were considered to be such consistent weights that they were used as standards on shopkeeper's scales. This concept spread right throughout Europe and was the origin of the 'carat' used by jewelers. This has now been standardized as 200 milligrams.
In the past, the carob has served as a valuable source of carbohydrate for working animals. Their declining numbers since the introduction of the internal combustion engine has greatly reduced demand for carob pods. The production of trees has diminished as a consequence. Carob has historically had a place as human food during famine and drought, during the Spanish civil war.
Russell Smith was an American, one of the first Americans to notice the use of carob and its merits as a human and animal food. He wrote reports and published books back about 1930. In Australia, carob was introduced about 1850 by immigrants. The pods are so hard and dry and long-lasting that it is easy to transport them about. So people were bringing them to their new land and planting them at the back of their blocks. You can see it on a lot of farms. In WA, in particular, there are some quite mature trees, around 100 years old. Between Perth and Geraldton, before the railway went in, there were water stops every 10 or 15 km. There are carobs growing at a lot of these water stops. Again, they were put in, not so much for the shade as for the packhorses and the camels that used the water stops.
It was likely introduced to the United States by the US patent office in the 1850s. It was 1950 when J. E. Coit promoted carobs in California. He introduced bud wood cultivars from Cypress, Israel, Tunisia, Greece, Yugoslavia, places around the Mediterranean rim. Seedlings are growing in many places as street trees, on verges. You can see them in Subiaco.
One of the dominant characteristics of the tree is the region it prefers. You can see that it very much hugs the coast, won't grow inland. The further inland you get, the more frost in winter and the more likely the tree will die. Similarly, it prefers low altitude, below 500 m. It grows best in about 500 to 700 mm rainfall. At less than 500 mm per year, you will get fruit set, but not much of a crop. It won't grow well in waterlogged areas. Generally, in the past, trees were growing on narrow-gutted, mongrel soils, rocky hillsides and slopes. They seem to tolerate some salt, 2 gm/litre, and can stand wind. Geraldton is a place where they are putting in lots of carob trees. They have a lot of strong wind up there. Some of the trees are growing sideways rather than upwards.
The domestication of the tree was based on shifting from sexual reproduction in the wild to vegetative propagation under cultivation. That is, because there was a lot of wild variability, farmers would have chosen the best of the wild plants, taken branches of them and grafted or budded them in their own orchards. The other problem with using wild trees, is that you don't know whether you are getting a male or a female. You have a good chance of ending up with 50% wasted space in an orchard.
Propagation was predominantly that of female clones, so that the carob productive area could be increased. You find that the main distinguishing features of domesticated trees over wild ones is the size of the bean, pulp quantity and sugar quantity.
The scientific name of the carob tree is Ceratonia siliqua, derived from the Greek word 'keras,' meaning a horn. And the Latin siliqua, alluding to the hardness and the shape of the pod. The common name originated from a Hebrew word, karoov, from which is derived the Arabic word, karoob, and later, algorobo, garafero, in Spain, karoobo, in Italy, karoobier, in French, St. John's Bread, and in German and a whole swag of names right through to Thailand, China and Malaysia that have their own names.
The genus belongs to the Leguminoseae family. It is a legume, but doesn't nodulate or fix nitrogen. The carob tree grows as an evergreen shrub to a height of about 10 metres, with a thick trunk and a broad, circular crown, dark brown bark, leaves about 10 to 20 cm long, about the shape of a 50 cent piece. Male and female flowers usually occur on separate trees. Inflorescences arise right on the trunk of the tree. It doesn't shed its leaves in autumn. There is also a hermaphrodite form. There are a few varieties of named hermaphrodites, particularly in America. There is one called Santa Fe, and there is a Clifford style that we have in Australia that was imported as cultivars. Generally you recognise a tree as female when you can see the immature bean in the flower.
There are some trees in Kalgoorlie that were producing fruit a few years ago, and then they turned into hermaphrodites. We think it may be because they were stressed during a drought.
Pods from the same tree can take various forms: they can be long and straight, or curly and twisted. The pods are easy to break open. The inside is soft with many seeds.
Many aspects of carob reproduction, such as the floral biology, pollination, compatibility between different sex types and cultivars, remain largely unknown. A lot of research is happening at the moment, slowly and steadily. It becomes important when you choose an orchard what the span of flowering of males and females is. Fortunately, there can be a long period of flowering. If they don't all flower together, there is a good likelihood that there will be an overlap.
Floral morphology is quite complex. A lot of discussion is going on about how to describe them, such as the length of filaments in the male flower. And whether a hermaphrodite has fully-developed stamens and pistils. All sorts of different combinations have been debated. As it turns out, the simplest is just to say there are male flowers, female flowers and hermaphrodites.
I mentioned that carobs usually flower in autumn. It will go on up to the rains. Male flowers have quite a pungent smell. Flowering time depends on local conditions. We had a mild summer here and trees are flowering for quite a long period. If you go further inland where the summer was hot and dry, chances are the flowers were in full bloom in the summer time. Flowering season generally lasts two or three months.
Pollination transport is effected by insects, bees, wasps and night-flying moths, and also by the wind. There is a lot of debate about what is the best method of pollinating trees. There have been instances of isolated female trees that have a lot of pods, even though there are no males around. You wonder how on earth did they do it. Perhaps there is wind-borne pollen coming from another suburb.
Shedding of the flower takes place in late autumn after the first rains come. Young fruit start to develop. The growing period is a full ten months. By spring time, the pods are full size but are totally green, with about 70% water content. The pods mature about February and March in Australia with about 12 to 20% moisture content. When they are fully turned brown, they are ripe. If your tongue starts to curl up when you taste one, you know it is not yet fully ripe. They can be very astringent.
The two main constituents of the pod are the pulp and the seed. The pulp constitutes about 90% of the pod by weight, and the remaining 10% is seed. The chemical composition of the pod depends on the cultivar and the harvest time. The pod can have as much as 50% sugar which is made up of sucrose, glucose and fructose. The tannins constitute 18 to 20%. There are some trace elements such as calcium, potassium, magnesium, sodium, copper, iron, manganese and zinc. There are saturated and unsaturated fats. Other experimenters have found five amino acids. But, there is very little protein, only about 1 or 2% digestible protein. The protein comes more from the germ of the seed than the rest of the pod. What protein there is in the pod is low in digestibility because it is bound up with the tannins and the fibre, so it is of no great value. It is good value as a carbohydrate. For that reason it is often used as a filler in other foods. You would mix up some lupins and perhaps put in 10 or 20% carob to give you a good carbohydrate balance with the protein in the lupins, a well-balanced meal. Generally, the food value of carob pods is similar to barley.
The seed consists of three parts: a coat, about 30% by weight; the endosperm; and the germ, another 30%. Seed coat contains antioxidants. The endosperm contains the carob bean gum. This is the part that has the most uses, and it is very expensive stuff. If you can grow a lot of it, you have a chance of making your crop economically viable. The two most important properties of the gum are the high water-binding capacity, to form viscous, stable solutions in high dilutions, and its potential to interact with other polysaccharides. It is very viscous in water, and has a high temperature range as well. There are the functions of adhesion, binding, body agent, crystallisation inhibitor, clouding agent, dietary fibre, foam stabiliser, gelling agent, moulding, protective colloidal, sterilising agent, and so on, and as a thickening agent in jams and pies, yogurts and sauces. The gum is called B410 in the food additive code book. The gum is used in pharmaceuticals, cosmetics, emulsions, textiles, foams, paper, chemicals, glue, colourings, dyes, pesticides, petroleum, mining, well-sinking, concrete-strengthening, and explosives.
Regarding genetic variability, this is a list of some of the cultivars around the world. It doesn't include the Spanish ones, a list of about 20. We have a number of these in Australia. There is one from Tunisia called Sfax, we have Tylliria from Cypress. Santa Fe, Clifford, and we have some local genetic types. Bath is used a lot in South Australia. Because of the infancy of the industry in Australia, there are a lot that aren't shown. So, there is an indication of what you can get. Each one has been described in terms of composition, sugars, tannins, and any other taste qualities about it. If one wanted one of those, they can be gotten.
To give an indication of how wide the variability, here are 28 we have looked at in Australia. A lot of these are trees that are people's favourites: 'Chookhouse No. 3.' You see there is a lot of variability, between length and width, the number of seeds in a pod, the weight of pods, seed weight, etc. Pod colour, pod surface characteristics, internal pulp colour variations, percentage moisture, percentage sucrose, average dry weight, shape of pod. This is some original research we have done, 5 to 8 years ago. It was done through Curtin University.
Making a selection for a good cultivar depends on many things. Sex is important: you mainly want females in the orchard. You want resistance to environmental factors, such as drought tolerance, frost tolerance. Most trees are quite sensitive to frost. You are looking for high yields, regular bearing. You want the varieties in your orchard to have the same pollinating times. It is worth noting that a lot of cultivars are alternate bearing. You will get a good crop one year and the crop the next year might be just a fraction of that.
The other qualities you are looking for are fruit quality. Pulp can range from 70 to 90% of the total weight. Seed yield can range between 5 and 27%. The first time I met Juan Tous, we took him around to a number of trees we though were good-looking trees. We cut pods open and chewed them and said, "Yes, this is a good tree, very tasty." But Dr. Tous was shaking the pods to find out how many seeds were in it. The value in the carob tree is more in the seed, than in the pulp. It was an eye-opener for us.
The content and quality of the gum can vary between cultivars, between 40 and 60% dry weight. Pod flavour can change. If you are growing it for human consumption, it is important to look at sugar, which can vary between 30 and 60%. Sugar is not always your complete answer. Santa Fe cultivar was rated top in a taste test not only because it had a sweet flavour, it had a nutty flavour as well. It was only about 47% sugar.
Ease of harvesting is important, whether you use manual shaking of branches or you are using a tree shaker. The important thing about those is that you then need to have all the fruit ripen at the same time, and will they actually drop. Tree vigour is important. They can reach heights of 6 to 10 metres. The fruit-bearing branches usually droop, obscuring the trunk from a tree shaker.
Carob has traditionally been used as an animal and human food. The pods provide fodder for all sorts of animals. The branches and leaves can be browsed. Currently the main use is the extraction of gum from the seed. It provides a timber which is hard and close-grained. It has been used for utensils, and also for slow-burning charcoal.
The seeds can be removed, the pulp is cleaned, washed, roasted and ground into a fine powder and used for human nutrition. Mixed with lecithin and oil, it can be used as a coating on sweets, ginger, biscuits, etc. The powder can be made into bread, muffins, cakes and biscuits. It is well-known as a substitute for chocolate, and can be made into bars, buds, and used in the same way as chocolate. The ingredients listed on the label of a Fruit and Nut block are: skim milk powder, carob flour, vegetable oil, sultanas, peanuts and soy lecithin. Also, from local shops, the ultimate in decadence for this time of year is the Easter Egg, a carob egg with coconut flavour. One of the advantages of carob as a chocolate substitute is that it contains no caffeine or theobromine. A lot of parents praise the Lord for it at Easter time.
Carob powder is often used an an extender, up to about 30% in chocolate because it is cheaper. It is the same colour and more sugar. Carob syrup is another important product. Here is some that is being made in South Australia. It can be used as flavouring for milk. There are other carob products. A pure carob molasses comes from Libya. It is more like treacle. From Egypt, there is date paste mixed with carob molasses.
The seed coat contains tannins which can be extracted, and act as an antidiuretic. There is some Swiss research on using the pod as a medicine for diarrhoea as well. The kibble can be fermented and distilled and turned into alcohol. Microbial protein production can be done. The embryo, 30% of the seed weight, can be ground to produce a germ meal which is the protein part of the seed.
Carobs are also used as shade trees, and because it tolerates poor soils and is long-lived, it can also be used for reafforestation. It can be used as windbreaks because it is evergreen. One point that should be mentioned about using carob pods for animal feed, is that some Israeli research shows that there is some growth inhibition in cows when large quantities are fed. This is likely caused by the condensed tannins in the pods. So, the recommendation is that animals should not be fed more than about 20% of their diet on carob pods.
Commercial production of carob is concentrated in the Mediterranean region. Total carob production in the world is about 200,000 hectares. The European Union accounts for about 70% of that. Spain has the biggest plantings of 82,000 hectares. Italy, Morocco and Portugal are also significant.
The production of carob in the world has been declining rapidly over the last 50 years. It is down to about 310,000 tonnes. In 1950, it was 650,000 tonnes. In Spain, alone, production has dropped from 550,000 tonnes down to 150,000 tonnes. The main reasons are the low price, coupled with farming mechanism and coastal plain development. That is, the land has been converted to other uses. In Italy also, carob production has been halved, in Portugal production has dropped by 25%. The only one that has increased is Morocco. Production there is estimated to be about 26,000 tonnes. Some new orchards have been planted recently.
The orchard belonging to Andrew Gebhardt in South Australia is the first Australian one to come into production. There are about two to three thousand trees there, maybe four thousand. They are spaced about 10 m apart. Another orchard will be coming into production shortly in Burra in South Australia. Production from this one will also feed into the processing plant of Andrew Gebhardt, so they are starting to build up a bit of an industry over there.
There are a couple of orchards in York, including my own. My colleague has about 1500 trees. And Geraldton is another region here in the west that is starting to take off. There is lots of activity up there. They have some nice, friable, loamy soils that the trees like. It doesn't go into a wintering period, but grows all year long. And there is a fair amount of water in the ground. So, once the trees get their feet into the water, they grow very well. I know of 4 or 5 orchards each with about 2,000 trees.
In a well-managed orchard, you would look for production about 8 years after budding. The first fruit would be scanty, but then this increases every year as the trees grow and mature. I am only doing my orchard as a part-time thing; I don't really have the time to make it work properly.
Generally, you irrigate them for the first couple of years. After that, they will live quite happily on their own for the next 100 years. But if you want to get a good crop off them, you have to ensure they get at least 500 mm of rainfall. If you don't get 500 mm, then you would use some kind of trickle or minisprinkler as supplementary irrigation.
Propagation is from open-pollinated seeds. No work has been done on rootstocks to identify better rootstocks. We just select a vigourous-looking tree and grab the pods off it and germinate the seeds. They are grown in pots for a couple of years, and then you either graft or bud them in the pots or in the field. The seeds are quite hard; there are several treatments to assist germination. You can pour boiling water over the seeds and leave them overnight. Keep changing the water for a couple of days. The brown seed coat gets striated, and the seed swells. Once the seeds have swollen, they are planted. Other methods include sulfuric acid or gibberellic acid. Generally, water is a lot cheaper and is not as dangerous. I get 95% take with the water method.
I put the seeds between some super Chux on a baking tray, ideal temperature for germinating the seeds is 25 degrees. Just keep it moist for a couple of days. The little white radicles appear, and you pot the seeds. It is very simple.
You plant them in the ground when they are big enough to survive a rabbit or field mice, or they can be kept for grafting or budding in the pots. Some people claim to succeed with grafting in the pots. A man in Alice Springs has been doing bench grafting on 10,000 seedlings this year. In Perth, we have tried to do chip buds on potted plants without success. Some people can do whip and tongue grafts on pot plants. I'm doing saddle grafts and whip and tongues at the moment in my back yard. The accepted practice is to plant them out in the field first, and when they are about as thick as your finger or your thumb, that is the time to do budding and grafting. That might be up to two years after they have been planted out in the field.
Micropropagation has been tried as well. This is a vegetative style, where you take a cutting of a green shoot, put it in some rooting hormone, and try to get roots coming out of that. They have been able to do it in Europe. But, generally, it produces a fibrous root with no main tap root, unlike the original one which is a nice strong tap root that goes right down. If you need the tree to be drought tolerant, this method will not produce it.
Seedlings are transplanted in spring time, after the danger of frosts. Young seedlings will die at minus 4 degrees. A lot of people say these trees are just born to die, and one of the reasons is that they plant them during the winter time. So, if you know this, you plant them in the spring time, but unfortunately, then you need to water them.
Budding is done by conventional methods, chip bud, patch bud, T bud, and is generally done in spring when the bark is starting to slip. The orchard in Burra was done using saddle grafts. A saddle graft....(end of tape)
...Orchard design. Here is a sample of how it can be done. It is probably similar to any other fruit tree orchard. Option A has an 8 x 5 (metre) spacing that will allow 250 trees per hectare. Eventually the trees are going to crowd each other out, so some would be removed, and you would end up with a 10 x 8 spacing. It could take 10 to 15 years for this to happen. Option B is putting them in even denser. This is a three-stage process of tree removal over time, ending up with a spacing of 10 x 10.
Option A has been used in California in the past. Portugal tends to use a geometry of 6 x 8 metres, which allows about 200 trees/hectare. Spain uses 8 x 9 in dryland conditions. The orchards going in in WA are generally 6 x 8 metres, 6 metres between trees and 8 metres between rows.
Traditionally, orchards have been pollinated by keeping a male branch on the rootstock and then putting female branches next door to them on the same rootstock. There is a lot of extra work involved in that. The recommendation now is that you have alternate rows of completely females. The centre row contains male or hermaphrodite trees with grouped clusters of 8 females (counting those in the 2 all-female rows) surrounding them.
F F F F F F F F F F
F M F F M F F M F
FF F F F F F F F F
The trees generally require very little pruning. There is only light pruning once the basic framework of the tree is established. The shape you would use would depend on the method of harvesting, manual with sticks, or a mechanical harvester. There are essentially two shapes that are used: the free vase shape and the modified central axis. The best time for pruning is autumn, immediately after the collection of the fruit. On established trees, pruning might be needed only every three or four years.
Traditionally, there has been very little fertiliser added to these trees. Because they don't nodulate, addition of nitrogen in the fertiliser is quite beneficial. Traditional orchards would use an NPK of 50,20,50, part given in autumn and the second part in spring. Dr. Tous has done research showing that fertilising with pure N increases production. The more N, the greater the production, and it didn't seem to plateau. So, it will live without fertiliser, but does respond vigourously to it. If you are doing a commercial operation, you certainly should build fertiliser into your equation.
Irrigation, generally, is only done occasionally, in order to make up to 500 mm of rainfall. When there is 500 mm of winter rainfall in an area that has long, hot, dry summers, then more needs to be supplied by irrigation. Mulching helps.
Carobs are normally free of insect pests and diseases in Australia. Carob moth, mildew disease, a Leopard moth can harm the pods. There are some bugs that suck moisture out of young seedlings, within a couple of days. The big pests are the birds, kangaroos and rats. Ringbarking is a particular problem. Cattle, horses, sheep, will browse on the foliage.
Yield begins between 6 and 8 years, and production increases up to about 20 or 25 years when they tend to plateau. We look at a yield of about 50 kg per tree in dryland conditions. Irrigated trees, well-cared for, could yield up to 100 kg per tree. Some big, isolated trees can produce up to 300 kg, some have produced up to a tonne in some years.
Harvesting is done either by shaking the trees or hitting them with sticks, which is the traditional method used in Europe. It is similar to the harvesting of olives. Mechanical tree shakers have been tried recently. The orchard in Burra was harvested last year with a tree shaker. They were getting through five trees in a minute. That was the easy part. The bottleneck was what you do with all the pods so suddenly. You need more than just a shaker--perhaps a conveyer belt system.
Here is a flow-chart on what happens in processing. The farmer shakes the tree, collects the pods, they go in the kibbler which separates the pod from the seeds. The pod gets roasted and ground into a powder. There could be a couple of steps in this depending on what you are making it for. Some of the pod might go off to an animal feed plant, and the pods are crushed down to various sizes, depending on the target animal. If it is going to be used for humans, it has different processing to make fine powder. The seed goes another way. The kernel is split, the seed coat is taken off either by an acid bath or roasting. The germ and endosperm are split apart, and then ground separately.
The economics of growing an orchard. Dr. Digby Rice in NSW was commissioned by the Rural Industries Research and Development Corp. to do a study on using carob as an agroforestry product in the low rainfall area of the Murray Valley. Over the course of 12 months he produced a report with these two tables. One uses an irrigated orchard with the expectation of getting 100 kg per tree. He considered a model of 100 hectare and a 20 hectare orchard. It highlights a decline in the economic return. So you get a good return when you are looking for seed and powder as the final product. If it is seed and stockfeed, there is a 2% return. If it is stockfeed only, the return is -3%. A linear planting is a windbreak or hedge. So, he is thinking only of buying a property, fencing it and planting a windbreak around it. The second table reconfirms the information on the first table, looking at a payback period of 2 years. (More discussion of these tables, incomprehensible without seeing the actual things.) So, the figures don't look good for a pure carob orchard. If you are doing carob as an adjunct to some other agricultural business, the figures change quite a lot.