Progress 01/01/05 to 12/31/08
Outputs
OUTPUTS: Results from this project have been presented at several international meetings, and 4 publications have been published in referred journals. The overall goal of this research is to investigate the contribution of starch molecular and granular structure to its swelling and leaching characteristics. A mechanism has been proposed to explain the formation of granule surface structure that is responsible for maintaining starch integrity during swelling and eventually breakdown and explains the changes in molecular size during leaching at different temperatures. When subjected to high temperature and excess water, starch swells as a result of increased mobility and interaction with water. Starch molecules become mobile and are capable of interacting or associating with each other. At the same time, smaller molecules, either more linear or smaller hydrodynamic volume, can leach out of the membrane-like surface structure. The surface structure is proposed to form through the interactions from starch molecules and described as a screen-like pocket with different sizes of opening to allow for passing of molecules. Larger molecular-weight molecules are more likely to become entangled and stay at the surface as part of granule surface, whereas lower molecular-weight molecules are easier to leach out with increasing temperature. When the amount of starch molecules is not sufficient to maintain granule integrity with increasing swelling, starch granular structure eventually collapses and forms fragments (ghost remnants) with the larger molecular-weight molecules still constitute the structure of ghost remnants. It is also suggested that more amylose exists in the random coil form at the core, whereas more amylose interacts with amylopectin at the outer layer for amylose-containing starches. The interaction of amylose and amylopectin may reduce the mobility of amylose that is present mostly in the amorphous lamellae, thus resulting in a higher glass transition in the amorphous lamellae and consequently a higher transition temperature in the crystalline lamellae. PARTICIPANTS: Dr. James Patindol, Postdoctoral Research Associate. Dr. Meng-I Kuo, Postdoctoral Research Associate. Dr. Linfeng Wang, Postdoctoral Research Associate. Daris Kuakpetoon, doctoral student. Mr. Kuakpetoon worked on starch structure-functionality relation as part of his doctoral dissertation project. He successfully finished the project and published the results in referred journals. TARGET AUDIENCES: The understanding of starch structure, functionality, and modification will provide a scientific basis for the food industry to select appropriate starch and modification for specific application. The results can also serve as guidelines for breeders and biotechnologists to produce novel starch based on end applications. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Understanding the mechanism of starch swelling and leaching is critical to the development of novel starches with desired functionality via breeding, biotechnology or modification techniques. This study has provided fundamental knowledge on the mechanism and structures that control swelling and leaching of starch. The knowledge gained from this work will allow advances in starch research. Plant breeders and biotechnologists will also be able to select the appropriate genes or enzymes to manipulate the biosynthesis of starch to produce desired structure and subsequently targeted properties. The ultimate goal of this study is to produce enhanced quality of foods from the incorporation of novel starch ingredients with improved functionalities.
Publications
- Kuo, M.-I, and Wang, Y.-J. 2006. Effects of Urea Concentration on Thermal and Rheological Properties of Rice Starches. Cereal Chem. 83:478-481.
- Kuakpetoon, D., and Wang, Y.-J. 2006. Structural characteristics and physicochemical properties of oxidized corn starches varying in amylose content. Carbohydr. Res. 341:1896-915.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Results from this project duration have been reported in a poster presented at Institute of Food Technologists annual meeting in Chicago in July 2007, and published in referred journals. The overall goal of this research is to investigate the contribution of interactions between starch components, starch molecular structure, and starch granule structure to the leaching characteristics, swelling behavior, and granule integrity of starch. The specific objective accomplished during this period was studying the leaching characteristics of starches varying in amylose content. Based on the results, a mechanism has been proposed to explain the formation of granule envelope responsible for maintaining starch integrity during swelling and in ghost remnants. Upon gelatinization, starch molecules become mobile and are capable of interacting or associating with each other. At the same time, smaller molecule, either more linear or smaller hydrodynamic volume can leach out because the
granule is maintained through molecular interaction, which is like a screened pocket with different sizes of opening to allow for molecules' movement. When temperature increases, starch absorbs more water and starch molecular mobility increases accordingly. Nevertheless, molecules can not leach out freely because of the presence of a screen-like surface. Larger molecular-weight molecules are more likely to become entangled and stay at the surface as part of granule envelope, whereas lower MW molecules are more easily to leach out with increasing temperature. When the amount of starch molecules are not sufficient to maintain granule integrity during continuing swelling, starch granular structure eventually collapses and forms fragments (ghost remnants) with the larger molecular-weight molecules still constitute the structure of ghost remnants.
PARTICIPANTS: Dr. James Patindol, Postdoctoral Research Associate. Daris Kuakpetoon, doctoral student. Mr. Kuakpetoon worked on starch structure-functionality relation as part of his doctoral dissertation project. He successfully finished the project and published the results in referred journals.
TARGET AUDIENCES: The understanding of starch structure, functionality, and modification will provide a scientific basis for the food industry to select appropriate starch and modification for specific application. The results can also serve as guidelines for breeders and biotechnologists to produce novel starch based on end applications.
Impacts
The results show that starch surface is not responsible for maintaining granule integrity during swelling. When starch surface was gelatinized and removed, the remaining granule samples heated in excess water at 85 degree C for 30 min still absorbed water and swelled to even greater extents compared with the native counterpart. On the other hand, the gelatinization temperature and enthalpy decreased with increasing surface removal for all remaining granule samples when compared with their native counterparts. The amounts of granule envelope and its amylose content were lower at 95 degree C than at 85 degree C, and both increased with increasing amylose content in the native starch. Amylopectin in granule envelope had significantly larger molecular weight and radius of gyration but slightly smaller polydispersity at 95 degree C than at 85 degree C. The results indicate that amylopectin with larger molecular weight and radius of gyration indeed was not as easy to be
solubilized during heating. Thereafter, granule envelope consisted of more amylopectin of larger molecular weight and radius of gyration with increasing temperature. Understanding the mechanism of starch swelling and leaching is critical in the development of novel starches with desired functionality by way of plant breeding or modern biotechnology. This study has provided fundamental knowledge on what really control swelling and integrity of starch. The knowledge gained from this work will allow advances in applied research with major breakthroughs in starch research. Plant breeders and biotechnologists will also be able to select the appropriate genes or enzymes to manipulate the biosynthesis of starch with controlled structure and targeted properties. The ultimate goal of this study is to produce improved quality foods by permitting rational modification of processing methods, and by providing targets to enhance the value of raw materials.
Publications
- Wang, Y.-J., Kuo, M.-I, Patindol, J., Wang, L. 2007. Chemical composition and structure of granule periphery and envelope remnant of rice starches as revealed by chemical surface gelatinization. Starch/Staerke 59:445-453.
- Kuakpetoon, D., and Wang, Y.-J. 2007. Internal structure and physicochemical properties of corn starches as revealed by chemical surface gelatinization. Carbohydr. Res. 342:2253-2263.
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Progress 01/01/06 to 01/01/07
Outputs
This research investigates the contribution of starch molecular structure and starch granule microstructure to the leaching characteristics, swelling behavior, and granule integrity of starch. The interaction among starch molecules is studied by treating starch with varying concentration of hydrogen bond-breaking agent, urea. The maximum values of G (storage modulus, G max) and G (loss modulus, G max, data not shown) of Wells rice starch of 18% amylose content were higher and increased with increasing urea concentration when compared with those of waxy rice starch at small deformation. The G and G of waxy rice starch were significantly lower and increased with increasing urea concentration from 0 to 10% but decreased when urea concentration was further increased from 15 to 20%. The interaction between amylose and amylose/amylopectin is suggested to contribute to the larger G max and G max and to the continuing increase in G and G from 0 to 20% urea concentration for
Wells rice starch. It is proposed that the interactions between amylose and amylopectin are stronger than those within amylopectin molecules. When starch is surface-removed to different degrees and the remaining granule sample is heated in excess water at 85 degree C for 30 min, it still exhibits swelling power and swells to even greater extents. The most increase in swelling power is observed when the outmost 10% starch surface is removed. On the other hand, the gelatinization temperature and enthalpy decrease with increasing surface removal for all remaining granule samples when compared with their native counterparts. The decrease in gelatinization enthalpy supports the less organized structure in starch center, i.e. hilum, whereas the decrease in onset and peak gelatinization temperatures with increasing surface removal suggest that amylose at the center may exist predominantly in the random coil form, which helps lower the gelatinization temperature. It is possible that more
amylose exists in the random coil form at the core, whereas more amylose interacts with amylopectin at the outer layer. The interaction of amylose and amylopectin may decrease the mobility of amylose that is present mostly in the amorphous lamellae, thus resulting in a higher glass transition in the amorphous lamellae and consequently a higher onset temperature in the crystalline lamellae. Additionally, the strong interaction between amylose and amylopectin near starch surface may strengthen granule structure and exert restriction or augment starch swelling. Similar results have also been found in corn starches with varying amylose contents.
Impacts
Understanding the mechanism of starch swelling and leaching is critical in the development of novel starches with desired functionality by way of plant breeding or modern biotechnology. This study has provided fundamental knowledge on what really control swelling and integrity of starch. The knowledge gained from this work will allow advances in applied research with major breakthroughs in starch research. Plant breeders and biotechnologists will also be able to select the appropriate genes or enzymes to manipulate the biosynthesis of starch with controlled structure and targeted properties. The ultimate goal of this study is to produce improved quality foods by permitting rational modification of processing methods, and by providing targets to enhance the value of raw materials.
Publications
- Kuo, M.-I, and Wang, Y.-J. 2006. Effects of Urea Concentration on Thermal and Rheological Properties of Rice Starches. Cereal Chem. 83:478-481.
- Kuakpetoon, D., and Wang, Y.-J. 2006. Structural characteristics and physicochemical properties of oxidized corn starches varying in amylose content. Carbohydr. Res. 341:1896-915.
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Progress 01/01/05 to 12/31/05
Outputs
This research investigates the contribution of starch molecular structure and starch granule microstructure to the leaching characteristics, swelling behavior, and granule integrity of starch. Amylose is found to be more concentrated at the core for Bengal starch, a medium-grain rice, and Wells starch, a long-grain rice. The trend for Dixiebelle, a higher amylose long-grain rice, is not as obvious as Bengal and Wells. The ungelatinized remaining starch does not disintegrate upon heating. Instead, the ungelatinized remaining granule still exhibits gelatinization transition, and can swell to a greater degree when the surface is removed to a greater extent for all three rice starches. The smaller enthalpies of the ungelatinized remaining granule samples suggest a less ordered structure at the core of starch. The structure and composition of remnant at 85 degree C and 95 degree C are different from those of 5-10% gelatinized peripheral starch. Amylopectin of remnant
treated at 85 degree C has different weight-average molecular weight (Mw) and z-average radius of gyration (Rz) and polydispersibility (Mw/Mn) compared with those of amylopectin treated at 95 degree C. The proposed mechanism of starch swelling and fragmentation during heating is proposed as that amylose and amylopectin leach during heating but more amylopectin molecules from the interior diffuse toward the periphery and interact with mostly amylopectin to contribute to the envelope-like structure. Starch surface and starch remnant do not share a common composition and structure, and starch surface structure is not responsible for maintaining starch granule integrity during heating and swelling. The envelope-like starch surface structure is not constant but dynamic during heating. The formation of envelope-like surface structure during heating is a result of molecular interaction after gelatinization.
Impacts
Understanding the mechanism of starch swelling and leaching is critical in the development of novel starches with desired functionality by way of plant breeding or modern biotechnology. This study will provide fundamental knowledge on what really control swelling and integrity of starch. The knowledge gained from this work will allow advances in applied research with major breakthroughs in starch research. Plant breeders and biotechnologists will also be able to select the appropriate genes or enzymes to manipulate the biosynthesis of starch with controlled structure and targeted properties. The ultimate goal of this study is to produce improved quality foods by permitting rational modification of processing methods, and by providing targets to enhance the value of raw materials.
Publications
- Wang, Y.-J., M.-I. Kuo, and L. Wang. 2005. Structure responsible for swelling and granule integrity of rice starch as revealed by surface chemical gelatinization. AACC International Annual Meeting (Abstract).
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