Microflora Contamination of Gum Arabic (Acacia Senegal Gum) From Tree to Store

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Mohammed, Abdel Rahman Ahmed
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This study comprises microbiological and physicochemical examination of 72 acacia senegal gum samples from the seasons 2002/03 and 2003/04. The samples were randomly collected from north and west kordofan areas, from fields, villages, markets and stores. all samples were randomly tested for viable count of bacteria, moulds and yeasts and thermophilic spore-formers, as well as some pathogens such as staphylococcus aureus, salmonella, and contamination indicators such as coliforms and faecal coliforms (e.coli) for 36 samples. Viable count of bacteria of gum samples after exudation ranged from 1.2×103 to 4.0×104colony-forming units/gram (cfu/g) while those taken after collection in the field showed a range from 2.8×103 to 2.2×104cfu/g, and those taken at village market ranged from 2.0×103 to 9.0×109cfu/g, and those taken at crops market showed a range from 5.0×102 to 8.0×103cfu/g. With samples of recent storage (three months) the count ranged from 3.1×103 to 8.0×103cfu/g, and with samples of long storage (one year) the count ranged from 3.1×103 to 4.5×103cfu/g. Viable count of moulds of gum arabic samples (after exudation, collection, village market, crops market, recent storage and long storage) showed a range from 8.0×102 to 1.7×104, 1.0×102 to 2.0×102, 2.0×102 to 8.0×102, 2.0×102 to 2.0×104, 1.0×102 to 2.0×103 and 3.0×102 to 6.0×102 cfu/g, respectively. Yeasts were not detected in any sample of gum arabic.Viable count of thermophilic spore-formers of gum arabic samples after exudation showed viable count ranging from 4.7×102 to 7.0×103cfu/g while those taken after collection showed a range from 1.2×103 to 3.5×103cfu/g. The samples at village market gave a range from 1.0×103 to 5.0×103cfu/g but the samples at crops market showed a range from 7.0×102 to 6.5×103cfu/g. The sample of recent storage gave a range from 2.3×103 to 5.0×104cfu/g, while samples of long storage gave a range from 3.5×103 to 3.1×104cfu/g. Coliforms were not detected except in eight samples; two samples drawn after collection in the field showed a low value of 3.6 /g and a high value of 2.4×103/g; one sample drawn at the village market showed a low value of 3.6/g; four samples drawn at crops market showed a value of 9.3×10/g, 4.3×10/g, 2.0×10/g and 3.6/g; and one sample drawn at recent storage showed a high value of 2.1×102/g. The ten isolates obtained were identified as klebsiella sp (8 isolates) and moraxella sp (2 isolates), which confirmed the absence of e. Coli. Staphylococci were not detected except in three samples (at village market, crops market and long storage). The suspected thirteen isolates obtained were identified as staphylococcus aureus (8 isolates), streptococcus faecium (4 isolates) and aerococcus viridians (1 isolate). The presence of salmonella was suspected in all samples except in samples after exudation. The fifteen suspected isolates were identified as salmonella sp (9 isolates), serratia sp (3 isolates), pseudomonas sp (2 isolates) and cedecea sp (1 isolates). On the other hand twelve isolates of gram-positive, rod-shaped bacteria were isolated and identified as bacillus sp, except that one isolate was found to be corynebacterium sp Physico-chemical characterization of the gum arabic samples including moisture, ash and crude protein content, ph, viscosity, optical rotation and mineral content was carried out. The samples after exudation, collection, at village market, crops market, recent storage and long storage showed that the mean value of moisture content was found to be 23.6%, 22.97%, 16.7%, 15.5%, 13.1%, and 11.6%; the ash content was 3.03%, 3.29%, 3.6%, 3.3%, 3.5% and 3.6%; the ph was 4.33, 4.33, 4.33, 4.37, 4.34 and 4.35; the protein content was 2.1%, 1.95%, 1.8%, 1.8%, 1.71% and 1.74%; the viscosity was 52.6, 53.87, 50.6, 53.9, 50.6 and 54.6 centipoises (cps)/sec; and the optical rotation was –25.8ْ , -25.0ْ , -27.2ْ , -28.0ْ , -29.2ْ and -26.5ْ , respectively . Also the mean value of the mineral composition for the gum arabic samples was 0.49%, 1.4%, 0.24% and 0.04% for ca++, k+, mg++ and na+, respectively, in the exudation samples; 0.85%, 1.39%, 0.31% and 0.04%, respectively, in the collection in field samples; 0.78%, 1.46%, 0.24% and 0.04%, respectively, in the village market samples; 0.65%, 1.59%, 0.29% and 0.02%, respectively, in the crops market samples; 0.63%, 1.28%, 0.27% and 0.09%, respectively, in the recent storage samples ; and 0.81%, 1.33%, 0.28% and 0.05%, respectively, in the long storage samples.
Gum Arabic, (Acacia Senegal Gum)