Sorghum and maize waxy starches were hydrophobically modified with octenylsuccinic anhydride (OSA... more Sorghum and maize waxy starches were hydrophobically modified with octenylsuccinic anhydride (OSA) and treated with enzymes before being used to emulsify β-carotene (beta,beta-carotene) and oil in water. Enzyme treatment with β-amylase resulted in emulsions that were broken (separated) earlier and suffered increased degradation of β-carotene, whereas treatment with pullulanase had little effect on emulsions. Combinations of surfactants with high and low hydrodynamic volume (V(h)) indicated that there is a relationship between V(h) and emulsion stability. Degree of branching (DB) had little direct influence on emulsions, though surfactants with the highest DB were poor emulsifiers due to their reduced molecular size. Results indicate that V(h) and branch length (including linear components) are the primary influences on octenylsuccinylated starches forming stable emulsions, due to the increased steric hindrance from short amphiphilic branches, consistent with current understanding of...
ABSTRACT A range of hyperbranched emulsifiers were prepared by reaction between starch and 2-octe... more ABSTRACT A range of hyperbranched emulsifiers were prepared by reaction between starch and 2-octen-1-yl succinic anhydride (OSA, commonly used in the food industry), under slightly basic conditions in water, leading to starches bearing hydrophobic OSA groups randomly distributed along the chains. By using different starch backbones and varying the amount of OSA during the synthesis, amphiphilic OSA-modified starches were obtained that formed aggregates in water and having controlled structural parameters. These parameters were characterized using 1H NMR, multiple-angle laser light scattering and size-exclusion chromatography. The critical aggregation concentration (CAC) was measured for samples with different levels of OSA modification, of macromolecular size and degree of starch branching. Increasing the dispersity in macromolecular size and/or degree of OSA substitution noticeably decreased the CAC. The results are interpreted in terms of the branching structure and conformation of the modified starches: all findings can be understood in terms of the various influences of molecular size, composition and flexibility. The structural factors affecting the CAC of large hyperbranched surfactants are found to be similar to those seen with smaller and simpler branched synthetic surfactants.
The effects of octenylsuccinic anhydride (OSA) modification of waxy maize and sorghum starches on... more The effects of octenylsuccinic anhydride (OSA) modification of waxy maize and sorghum starches on subsequent β-amylolysis are examined. Hydrolysis with β-amylase is a method by which OSA starches may be structurally modified for industrial purposes. The hydrolysis of both granular and gelatinised forms of both starches follows first-order kinetics regardless of the OSA used as a percent of starch mass (0-24%). The highest hydrolysis rate coefficients for granular starches are at modification with 6% OSA/starch. The largest molecular sizes of β-amylase hydrolysed OSA-modified gelatinised starches are found at modification with 24% OSA/starch. The results suggest that octenylsuccinyl groups have an action-blocking effect on β-amylolysis of gelatinised starch, but the effect of semi-crystalline granular structure is more pronounced than that of OSA modification. Hence β-amylolysis can be used under appropriate conditions to modify the structure of gelatinised OSA-modified starches.
International Journal of Biological Macromolecules, 2021
The objectives of this study were to debranch waxy maize starch by pullulanase, produce spherulit... more The objectives of this study were to debranch waxy maize starch by pullulanase, produce spherulites with different crystalline structures and birefringent properties by controlling crystallization conditions and determine how their structures were correlated with their digestibilities. The spherulites formed in water or 50% ethanol at 4 °C had a B-type crystalline structure. The birefringence sign was not uniform for the spherulites formed in water at 4 °C; some spherulites displayed negative birefringence. However, positive birefringence was observed for the spherulites formed in 50% ethanol at 4 °C, indicating starch chains were radially arranged. The spherulites crystallized in water at 50 °C followed by further crystallization at 4 °C had a predominate A-type crystalline pattern with positive birefringence in some particles, the highest resistant starch content (73.0%) and the highest degree of crystallinity (76%).
Sorghum and maize waxy starches were hydrophobically modified with octenylsuccinic anhydride (OSA... more Sorghum and maize waxy starches were hydrophobically modified with octenylsuccinic anhydride (OSA) and treated with enzymes before being used to emulsify β-carotene (beta,beta-carotene) and oil in water. Enzyme treatment with β-amylase resulted in emulsions that were broken (separated) earlier and suffered increased degradation of β-carotene, whereas treatment with pullulanase had little effect on emulsions. Combinations of surfactants with high and low hydrodynamic volume (V(h)) indicated that there is a relationship between V(h) and emulsion stability. Degree of branching (DB) had little direct influence on emulsions, though surfactants with the highest DB were poor emulsifiers due to their reduced molecular size. Results indicate that V(h) and branch length (including linear components) are the primary influences on octenylsuccinylated starches forming stable emulsions, due to the increased steric hindrance from short amphiphilic branches, consistent with current understanding of...
ABSTRACT A range of hyperbranched emulsifiers were prepared by reaction between starch and 2-octe... more ABSTRACT A range of hyperbranched emulsifiers were prepared by reaction between starch and 2-octen-1-yl succinic anhydride (OSA, commonly used in the food industry), under slightly basic conditions in water, leading to starches bearing hydrophobic OSA groups randomly distributed along the chains. By using different starch backbones and varying the amount of OSA during the synthesis, amphiphilic OSA-modified starches were obtained that formed aggregates in water and having controlled structural parameters. These parameters were characterized using 1H NMR, multiple-angle laser light scattering and size-exclusion chromatography. The critical aggregation concentration (CAC) was measured for samples with different levels of OSA modification, of macromolecular size and degree of starch branching. Increasing the dispersity in macromolecular size and/or degree of OSA substitution noticeably decreased the CAC. The results are interpreted in terms of the branching structure and conformation of the modified starches: all findings can be understood in terms of the various influences of molecular size, composition and flexibility. The structural factors affecting the CAC of large hyperbranched surfactants are found to be similar to those seen with smaller and simpler branched synthetic surfactants.
The effects of octenylsuccinic anhydride (OSA) modification of waxy maize and sorghum starches on... more The effects of octenylsuccinic anhydride (OSA) modification of waxy maize and sorghum starches on subsequent β-amylolysis are examined. Hydrolysis with β-amylase is a method by which OSA starches may be structurally modified for industrial purposes. The hydrolysis of both granular and gelatinised forms of both starches follows first-order kinetics regardless of the OSA used as a percent of starch mass (0-24%). The highest hydrolysis rate coefficients for granular starches are at modification with 6% OSA/starch. The largest molecular sizes of β-amylase hydrolysed OSA-modified gelatinised starches are found at modification with 24% OSA/starch. The results suggest that octenylsuccinyl groups have an action-blocking effect on β-amylolysis of gelatinised starch, but the effect of semi-crystalline granular structure is more pronounced than that of OSA modification. Hence β-amylolysis can be used under appropriate conditions to modify the structure of gelatinised OSA-modified starches.
International Journal of Biological Macromolecules, 2021
The objectives of this study were to debranch waxy maize starch by pullulanase, produce spherulit... more The objectives of this study were to debranch waxy maize starch by pullulanase, produce spherulites with different crystalline structures and birefringent properties by controlling crystallization conditions and determine how their structures were correlated with their digestibilities. The spherulites formed in water or 50% ethanol at 4 °C had a B-type crystalline structure. The birefringence sign was not uniform for the spherulites formed in water at 4 °C; some spherulites displayed negative birefringence. However, positive birefringence was observed for the spherulites formed in 50% ethanol at 4 °C, indicating starch chains were radially arranged. The spherulites crystallized in water at 50 °C followed by further crystallization at 4 °C had a predominate A-type crystalline pattern with positive birefringence in some particles, the highest resistant starch content (73.0%) and the highest degree of crystallinity (76%).
Uploads
Papers by Michael Sweedman