Gum acacia structural features and emulsion stability
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The structure-function relationship of commercial gum acacia (GA) from Acacia senegal (SG1, SG2 and SG3) and Acacia seyal (SY1 and SY2) were studied. The protein content was less than 0.9 µg/mg (p>0.05) and ζ-potential was less than -32 mV (p>0.05). The effective diameter was between 172 to 257 nm and in the order SG2<SG3<SG1 and SY2<SY1 for the two types gums. A linear regression relationship between sample concentration and 1-anilinonaphthalene-8-sulfonic acid (ANS) relative fluorescence intensity was observed, indicating surface hydrophobicity was significantly different in the order of SG2>SG3>SG1>SY1>SY2. Raman, FT-IR spectra peaks and peak ratios of protein to carbohydrate provided additional structural information. The stability of emulsions, prepared with the gums, during a 6-day storage study at 4, 25, 30ºC, indicated that emulsion stability was greater in SG than SY samples at the first day of storage. The rate of sedimentation, creaming and particle size changes varied between gums stabilized emulsions according to gum type, surface hydrophobicity, and effective diameter. Particle size distribution (PSD) increased as surface area or volume distribution for emulsions stabilized by SG or SY, respectively.