Journal of Cereal Science 30 (1999) 133–145 Article No. jcrs.1999.0266, available online at http://www.idealibrary.com on Influence of Technological Modifications of the Protein Network from Pasta on in vitro Starch Degradation A. Fardet*, J. Abecassis§, C. Hoebler*, P. M. Baldwin†, A. Bule ´on‡, S. Be ´rot¶ and J.-L. Barry* * Laboratoire des Fonctions Digestives et de Nutrition Humaine, Institut National de la Recherche Agronomique, Rue de la Ge ´ raudie ` re, B.P.71627, 44316 Nantes Ce ´ dex 03, France; † Laboratoire de Biochimie et Technologie des Glucides, Institut National de la Recherche Agronomique, Rue de la Ge ´ raudie ` re, B.P.71627, 44316 Nantes Ce ´ dex 03, France; ‡ Laboratoire de Physico-Chimie des Macromole ´ cules, Institut National de la Recherche Agronomique, Rue de la Ge ´ raudie ` re, B.P.71627, 44316 Nantes Ce ´ dex 03, France; ¶ Laboratoire de Biochimie et Technologie des Prote ´ ines, Institut National de la Recherche Agronomique, Rue de la Ge ´ raudie ` re, B.P.71627, 44316 Nantes Ce ´ dex 03, France; § Laboratoire de Technologie des Ce ´ re ´ ales et des Agropolyme ` res, 2 Place Viala, 34060 Montpellier Ce ´ dex, France Received 19 August 1998 ABSTRACT The pasta protein network limits starch hydrolysis rate in vivo leading to low post-prandial glycemia. To better understand the mechanisms involved, various pasta products were processed to obtain protein network structures differing from that in reference pasta extruded at 40 °C and dried 17 h at 55 °C. After cooking, pasta strands were submitted to in vitro alpha-amylolysis. Compared to reference pasta, higher extrusion temperature (70 °C), high-temperature drying treatment (2 h at 90 °C) or autoclaving (115 °C for 15 or 40 min) had no marked effect on the rate of dextrin release from pasta particles. Protein enrichment at a 20%-level and flour fractionation-reconstruction with removal of insoluble fibre before pasta extrusion significantly (p<0·05) delayed ([1 h) the rate of dextrin release (-14% at 8 h). Confocal laser scanning microscopy allowed the three-dimensional structure of the protein network from protein-enriched pasta to be observed, and suggested that increased starch encapsulation may explain the reduced accessibility of starch to alpha-amylases. A stronger cohesiveness between starch and protein, due to insoluble fibre removal, was probably responsible for the decrease of starch accessibility to alpha-amylase in fractionated-reconstructed flour pasta. Modified geometrical characteristics (e.g., tortuosity) of the protein network were not correlated with starch degradation rates.  1999 Academic Press Keywords: pasta, protein networks, alpha-amylolysis. lorimetry; F max =maximum shear strength; RS=  : CLSM=confocal laser scanning Resistant starch; SDS=Slowly-Digestible Starch; microscopy; HSA=human salivary alpha-amylase; SI= SP ref =reference spaghetti; SP 40/HT =spaghetti extruded swelling index; DSC=differential scanning ca- as reference spaghetti extruded at 40 °C and dried at high temperature (2 h at 90 °C); SP 70/LT =spaghetti Corresponding author: Dr C. Hoebler extruded at 70 °C and dried as reference spaghetti at 0733–5210/99/090133+13 $0.00/0  1999 Academic Press