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Keywords:

  • Diffusion;
  • mechanisms;
  • first-order kinetics;
  • Fourier transform infra-red spectroscopy;
  • monophasic digestogram;
  • particle size;
  • starch gelatinisation

Summary

The kinetics of starch digestion in cryo- and hammer-milled sweet potato flours were investigated to reveal monophasic digestograms that were independent on particle size (80–390 μm), and suitably described (r2 > 0.98; P < 0.05) by a modified first-order model. Milling conditions significantly affected (P < 0.05) the particle size, salivary–gastric-digested starch and rate of starch digestion as the effective surface areas changed. The reciprocal of the rate of starch digestion (1/K, s) was significantly related to the square of the average particle size (size2, cm2), with the reciprocal of the slope (0.9–3.8 × 10−7 cm2 s−1) revealing diffusion-controlled digestion. The hammer-milled flours gave different digestion and functional parameters as frictional heat and glass transition phenomena played different roles in the overall structural changes in the flours. These parameters are discussed with starch digestion parameters in cereals and legumes to understand starch digestion in sweet potato.