Solution viscosity and structural modification of pumpkin biopectin

Solutions of ‘biopectin’ obtained from pumpkin pulp by digestion with the multi-enzyme culture supernatant from Bacillus polymyxa (strain 88A) were prepared in 0.10 M NaCl and characterised by rotational viscosity measurements at 20 °C. The resulting double-logarithmic plot of specific viscosity versus the product of concentration (c) and intrinsic viscosity ([η], from combined Huggins and Kraemer extrapolation to c=0) showed a sharp increase in slope at c[η]≈1 in comparison with the normal value of c[η]≈4 for disordered coils, suggesting a branched structure, possibly arising from Ca2+-mediated association of constituent chains.