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Keywords:

  • citrus fibre;
  • extrusion-cooking;
  • solubility;
  • viscosity;
  • starch degradation;
  • glucose diffusion

Abstract

Orange and lemon peels were extruded under controlled conditions of varying severity, and their physico-chemical characteristics and effect on the enzymatic hydrolysis of starch and glucose diffusion were studied. Extrusion-cooking treatment increased the soluble fraction of dietary fibre as well as solubilised pectic substances and arabino-galactomannan chains. The apparent viscosities of aqueous extracts of extruded fibre were increased slightly for orange and more markedly for lemon fibre. With both fibre sources, viscosities values were higher in Tris-maleate buffer (0.1 M) than in NaCl (154 mM). However, these modifications had no effect on starch hydrolysis and glucose diffusion in vitro.