Enzymatic Degradation and Analysis of Gum Arabic

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Abdalla, Ishraga Galal Eldin
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Authenticated gum Arabic samples, from A. Senegal and A. Seyal were characterised for moisture content, ash, optical rotation, pH, nitrogen content and intrinsic viscosity. The molecular weight was determined using GPC-MALLS system and was found to be in the range of 4.6x105--6.1x105 for A. Senegal and 25.5x105 for A. seyal. The effect of the enzyme on the molecular weight was investigated. The weight average molecular weight of A. Senegal samples is reduced up to 40% of the original weight after incubation with enzyme, while for A.seyal sample incubation with enzyme for 72hrs reduced the molecular weight by 43%. The enzyme –papain degraded A. Senegal completely within 24hrs incubation. The AGP completely disappeared. A. Seyal did not show reduction neither during the first 6hrs nor the 24hrs, but a slight reduction (14%) after 48hrs was observed. The mass recovery for AGP peak of A. Senegal( Commercial), A. Senegal (sinnar) and A. Senegal (Abuj.) have been reduced by 94.6, 95.9 and 97.2% respectively after 6hrs of incubation, and disappeared completely after 24hrs. For A. Seyal sample data obtained for the mass recovery showed:- - 7.4% and 59% after 24hrs and 72hrs respectively. A.Seyal has shown lower degradation compared to A. Senegal. This result can be attributed to the more highly branched and compact structure of A. Seyal compared to A. Senegal which sterically inhibits the enzyme from permeating into the molecular core. The effect of temperature was studied at two different temperatures 37C0 and 63C0 using Ultraviolet (UV) and light scattering. From the data obtained we can concluded that degradation of gum Arabic takes place at 63C0. The effect of temperature (above 60C0) on gum arabic molecular weight distribution has been studied. For A. Senegal at 63C0 the weight average molecular weight was slightly decrease by 22%. The mass recovery was changed from 113 to 111. The polydispersity was reduced from 2.2 to 2.0.The average weight molecular weight of AGP peak was increased and the mass recovery for AGP peak was decreased by (43-84%) after 6hrs, 24hrs and 48hrs. For AG peak no change was observed . The GP peak was increased by 13% and 9.0% respectively. For A. seyal the molecular weight was decreased by 14%, 39 and 48% after 6hrs, 24hrs and 48hrs respectively. The mass recover,slightly increased from 106 to 108, 109 and 107 after 6hrs, 24hrs and 48hrs respectively. The polydispersity was reduced from 3.6 to 3.2, 2.3 and 2.3 after 6hrs, 24hrs and 48hrs. The mass recovery for the AGP peak was reduced by 17%, 48% and 55% after 6hrs, 24hrs and 48hrs respectively .The average molecular weight for peak 1(AGP) reduced from 10.2x106 to 9.2x 106 , 5.4x106 and 4.91x106 after 6h, 24h and 48hrs respectively. The molecular weight for the AG peak was increased from 1.0x105 to 9.6x105 , 9.0x105 & 9.3x105 after 6hrs, 24hrs and 48hrs respectively, while the mass recovery was increased slightly. The molecular weight of A.Seyal sample was affected more than A.senegal samples. Heating gum Arabic solutions above 60co affect the molecular weight greatly where the number average molecular weight remained fairly constant( Mn= 19000-18000).Indicating no major structural modification. The rheological properties of gum Arabic samples were investigated using flow and oscillation measurement. A. Senegal and A. seyal have shown a Newtonian flow behaviour of gum concentration range 10- 50(w/w). A. Senegal was found to have a slight high elasticity than A. Seyal which was attributed to the protein content and structure of the AGP. The effect of enzyme on the shear viscosity for A. Senegal and A. seyal show shear thinning at low shear rate ( 0.1-1 S-1) and Newtonian flow at high shear rate > 1S-1. As the concentration of enzyme increase the shear viscosity decrease in this manner 1.6x10-3 > 1.6x10-4 > 1.6x10-6. It has shown that shear viscosity decreased from 5pa.s to 1, 2, and 3pa.s and from 9.0 to 6.0, 7.0 and 8.0 for treated gum solutions with 1.6x10-3, 1.6x10-4 and 1.6x10-6% concentration of papain enzyme respectively. The G`(elastic modulus) value for treated gum solution was decreased in this manner 1.4x10-3<1.4x10-4<1.4x10-6% concentration papain enzyme. At 1.4x10-3 the elastic modulus disappeared G`(negative values
Enzymatic,Degradation,Analysis,Gum Arabic