!38 JOURNAL OF TItE SOCIETY OF COSMETIC CHEMISTS

RECENT ADVANCES IN THE CHEMISTRY OF ACACIA GUMS 69 ent samples of gum arabic did not vary in properties to any great extent, but this is not the current industrial view botanically, Acacia senegal is variable. (Good quality modern Sudanese "gum arabic" is very largely the exudate from Acacia senegal trees, but the presence of some gum from other Acacia spp.--particularly A. laeta, A. seyal, and A. arabica--and from other genera [e.g. Albizia sericocephala (35)] must be expected to occur spas- modically). The Sudanese consider that the viscosity of a gum sample is dependent, amongst other factors, on the age of tree involved and un- published observations (36) have indicated that the optimum age of tree is in the range 10-15 years. In an extensive study, twelve samples of tapped gum from A. senegal trees growing in three different districts of the Sudan (chosen for their different soil profiles) were compared with 13 different single nodules of natural exudate gum, including three nodules from one tree (A), two nodules from tree B, and two from tree C these trees grew very close together. In addition, three "non-nodular" specimens ("NN") from A. senegal, a specimen ("BB") of gum exuded by a tree infested by wood-borer beetles, and a specimen of "Hennawi" gum ("HW") --a dark coloured, Table III Analytical data for bulk samples of Acacia senegal gum Sample Moisture Ash Nitrogen Insoluble* Flo•v-time number (cm3g -') •o •o •o % Crude gumt Purified gum:• õ QN1 12.8 3.64 0.33 0.4 57 25 (19.9) QN2 13.4 3.37 0.34 0.3 47 18 QN3 13.3 3.07 0.36 0.4 43 20 QN4 13.1 2.91 0.35 0.2 37 17 QN5 12.7 3.62 0.34 0.6 62 30 UR1 13.2 3.05 0.39 0.4 35 21 UR2 13.5 3.52 0.39 1.0 34 22 GG1 12.4 3.68 0.39 1.5 54 36 GG2 12.4 4.16 0.42 1.6 64 43 (24.5) GG3 12.9 3.98 0.41 1.3 67 36 GG4 13.0 3.93 0.38 0.5 79 38 GG5 13.2 3.81 0.38 0.2 71 32 NN1 13.4 3.88 0.40 0.4 83 36 NN2 13.2 3.70 0.34 0.2 62 36 NN3 13.1 3.97 0.39 0.3 70 35 HW 13.6 5.67 0.37 0.5 39 35 (20.6) Average 13.1 3.75 0.37 0.6 56 30 Range 12.4-13.6 2.91-5.67 0.33-0.42 0.2-! .6 34-83 17-43 Standard deviation 0.36 0.63 0.028 0.47 *Insoluble after 24 h in cold water t0.03 g ml -• in water at 25.0ø $0.03 g ml -• in 4 •o sodium chloride solution at 25.0ø õvalues in brackets are the correspondinglimiting (C-O) flow-time numbers. Reproduced from Carbohydrate Research, 6 97 (1968)