by Elwyn Hegarty
About 950 Australian Acacia species have been recorded. Nearly all of them appear to have edible seeds - on the basis of lack of evidence to the contrary - but the bushfood industry wisely prefers to use species that already have some history of safe use in traditional Aboriginal communities.
In central Australia, seeds from about 50 species were used. These included mulga (A aneura). In many cases, the pods were thrown on a fire for a short while to open, and to dry off any bitter substances in the pod that could spoil the taste of the seeds. The pods were threshed, and the seeds variously winnowed, yandyed, parched, pounded, ground, and made into a paste to be baked into cakes.
Aboriginal groups also ate the insect galls (raw or cooked), and various grubs that inhabited the trunks and branches of acacias, and the sweet exudates from lerp insects. The gum was made into balls and used in drinks, and was an important food, which in Victoria at least was used much more than the seeds. The roasted and peeled roots of some species were eaten, and leaves of others were burned for use in a sort of chewing tobacco.
A few species were avoided, including A ligulata, which had some reputation for "making your hair fall out" and Acacia georginae (Georgina gidgee) various parts of which can contain some fluoroacetate. This compound is the same as the commercial "1080" poison, used for vermin.
In coastal areas such as tropical Queensland where there was a wider, and probably more interesting and easily prepared, selection of potential foods, acacia seeds were not popular. It was recorded that of about 240 plants used there for traditional food a hundred years ago, only 7 were Acacias and the seeds of only two of these were eaten.
Uses in other traditional communities
Some years ago it was reported that there were 1 3/4 million hectares of plantations of Australian acacias. They are now grown in 70 countries, for various purposes.
A number of Australian acacias are being used in Niger and elsewhere in Africa as a component of human food, and other useful purposes such as firewood and windbreaks. This was the result of an ongoing aid program originating in Canberra (CSIRO Division of Forestry). Among the most popular were A. colei (formerly classified as a part of A. holosericea) and A. tumida. Although there are plenty of Acacia species in Africa, they are generally not considered for food use because they may contain compounds that can cause undesirable effects including muscle paralysis, renal failure and drowsiness. However, these latter problems are not known to have occurred in Australian aboriginal communities that used acacias as staple foods. In Africa these introduced Australian species regularly produce heavy crops of seed that can provide up to 30% of a normal diet.
It is interesting to read that the gums from some African acacias were seasonal staple foods of the Moors and Hottentots. Gum arabic is also derived from various acacia species
While leaves and other parts of various Australian acacias may contain sufficient quantities of compounds such as cyanogenic glucosides and saponins to make them unsuitable for stock or human food, acacia seeds as used for human food seem not to pose the same problems. The seeds themselves have an aril that is rich in oil, and a fairly thick seed coat that is very fibrous and not readily digested. Depending on whether the seed coat is included, the seeds can contain up to 20% of protein, about 8% of mostly unsaturated fats and oils, about 50% of carbohydrate - mostly starch rather than sugar - and additional fibre, as well as various other constituents such as potassium, which is often much more abundant than sodium. They are a good source of energy - averaging about 1500 kJ per 100 grams.
Green wattle seeds are quite similar in composition to cultivated garden peas. However, they are best cooked (usually by lightly baking) as all Australian species so far tested have had the property (if used raw in quantity) of inhibiting some of the enzymes of the digestive system. The same is true of soybeans and other legumes in our normal diet, which require cooking. As far as we know, Australian wattleseeds don’t accumulate toxic levels of heavy metals or selenium.
While for aboriginal peoples, quantity, accessibility, and high nutritive value were the most sought-after qualities in foodstuffs, bland tastes were frequent, especially where extensive detoxification had been required - for example in black beans, cycads and some yams. Now, the commercial bushfood industry tends to value flavour, appearance and lack of known toxicity more highly than nutrition, and its products are not normally dietary staples.
Wattleseeds are among the best commercial successes. Gundabluey (A. victoriae) is the most popular selection, partly because it is very widespread through inland and some coastal areas, grows quickly, and has fairly large seeds. But it’s normally quite prickly, which complicates seed gathering. Also, the seed crop is somewhat unreliable and has failed over large areas in some years. In these cases, more of other species are used. These might include A. longifolia (also called A. sophorae), A. notabilis, A. retinodes, and A. pycnantha.
Around Brisbane, A. fimbriata (Brisbane wattle) is one of the species that has been tried and seems to be well received. Mostly, commercial products are prepared by lightly baking the seed, then grinding it to a powder. The most popular commercial products containing wattleseed are breads, biscuits cakes, and ice cream. Wattleseed is gluten-free and so is suitable for particular diets, but in bread-making the absence of gluten affects the texture, and so wattleseed flour it is combined with a higher proportion of ordinary wheaten flour. Wattleseed could be a useful ingredient in diabetic diets, as the carbohydrates are absorbed quite slowly, so providing energy over a long period.
Brand Miller J, James KW & Maggiore PMW (1993). Tables of Composition of Australian Aboriginal Foods. Aboriginal Studies Press, Canberra.
House APN & Harwood CE (1992). Australian Dry-Zone Acacias for Human Food. CSIRO/Australian Tree Seed Centre, Canberra.
Lister, P.R., P. Holford, T. Haigh, and D.A. Morrison. 1996. Acacia in Australia: Ethnobotany and potential food crop. p.228-236. In: J. Janick (ed.), Progress in new crops. ASHS Press Alexandria VA. (see also http://www.hort.purdue.edu/newcrop/proceedings1996/v3-228.html).
Maslin BR (1999). Edible wattle seeds of southern Australia. Australian Plants 20 (159): 56-58.
Roth WM (1901-3). North Queensland Ethnography Bulletins 1-5.