Chemical composition of Acacia colei and Acacia tumida seeds—potential food sources in the semi-arid tropics

The seeds of Acacia colei (Maslin and Thomson) and A. tumida (F. Muell ex Benth.) are traditional foods of Australian Aboriginal people. Chemical analysis was carried out on seeds of A. colei trees growing in Maradi district, Niger Republic and A. tumida from a natural stand near Kunanurra in north western Australia. Crude protein (N × 6.25) ranged from 23.4% for whole A. colei seed to 30.6% for a water-processed A. colei sample and 20.4% for A. tumida. True proteins were 19.9, 25 and 18.5% and ether extracts 10.9, 18.9 and 8.1% for these samples, respectively. Amino acid analysis indicated that tryptophan was the first limiting amino acid in all the acacia samples. Dietary fibre, calculated on defatted and ethanol extracted samples, was highest in whole A. colei with the seed coat (47.9%) and lowest in the processed A. colei (31.9%). Total soluble sugar was highest in A. tumida (14.6%). Both A. colei and A. tumida seeds contained high levels of linoleic acid. Fat soluble vitamins (carotenoids, ergocalciferol and α-tocopherol) were generally inadequate while the water-soluble vitamins (B group) were in sufficient to large quantities. Processing A. colei with water reduced thiamine, niacin, riboflavin and pantothenic acid contents by 12, 31, 42 and 74%, respectively. Potassium was the predominant mineral in all the acacia samples. Iron, magnesium, calcium and zinc were in high concentrations; the availability of iron was low but that of other elements was adequate.