Pilot scale production and in vitro gastro-small intestinal digestion of self-assembled recrystallised starch (SARS) structures

Abstract

Two commercial maize starches (Hylon VII, HA7; and normal maize starch, MS) and a potato starch were processed in the presence of palmitic acid (C16:0, Palm) at 140 °C followed by retrogradation in order to produce self-assembled recrystallised starches (SARS). The new starch structures prepared from HA7 exhibited a stronger birefringence pattern under polarised light and greater relative crystallinity (%) than those prepared from potato and normal MS. Also, the SARS from HA7 showed a typical Vh pattern (2Ө: 8.5°, 15°, 23°) confirming a strong inclusion complexation between amylose and fatty acid. Effect of other fatty acids (stearic, C18:0 and oleic, C18:1) on SARS formation was also studied using HA7. The degree of relative crystallinity (%) of these samples showed an order of palmitic > oleic > stearic, with the former also showing greater yield (YSARS). The transition temperatures and enthalpies of melting or dissolution for SARS prepared from HA7 and three fatty acids (further referred to as HA7-SARS) ranged between 101 and 131 °C and 11–18jg−1, respectively. The scanning electron micrographs of the freeze-dried HA7-SARS showed the presence of aggregated round and disc/torus shaped morphologies in varying amounts. An in vitro starch digestion model was used to study the kinetics of glucose release during digestion of ground and cooked HA7-SARS for 120 min. All the HA7-SARS samples exhibited slower and significantly lower overall starch hydrolysis than the native HA7 starch (70%), with the SARS prepared using palmitic acid showing the lowest hydrolysis (44%). Digesta from the latter also showed the presence of intact microparticles resistant to gastro-small intestinal digestion.