Ultrastructural analysis of buckwheat starch components using atomic force microscopy.

UNLABELLED Morphological and structural features of buckwheat starch granules and nanocrystals were examined using atomic force microscopy and dynamic light scattering. Partially digested starch granules revealed a clear pattern of growth rings with the central core revealing lamellar structure. Atomic force microscopy and dynamic light scattering experiments revealed that the buckwheat starch granules were polygonal in shape and were in the range of 2 to 19 μm in diameter. The optimized acid hydrolysis process produced nanocrystals with the shape of spherical structure with lengths ranging from 120 to 200 nm, and the diameter from 4 to 30 nm from aqueous suspensions of buckwheat starch solution. The sorption isotherms on buckwheat starch nanocrystal/glycerol composite exhibited a 3-stage transition of moisture in the blending. The biocompatible nature of buckwheat starch nanocrystals and their structural properties make them a promising green nanocomposite material. PRACTICAL APPLICATION Buckwheat starches had never been studied on a nanoscale, but we have achieved new understanding of starch granule morphology and concentric growth rings using nanoscale imaging. Since buckwheat is an underutilized crop, we foresee the potential application of buckwheat starch, starch-based nanocrystals, and nanoparticles, to expand markets and encourage producers to expand their buckwheat acreage. The atomic force image analysis suggests that buckwheat starch could be used as a new biopolymer material in food industries.

[1]  A. Lynn,et al.  Starch granules large and small. , 1992, Biochemical Society transactions.

[2]  P. Hansma,et al.  Atomic force microscopy , 1990, Nature.

[3]  L. Rockland,et al.  Saturated Salt Solutions for Static Control of Relative Humidity between 5° and 40° C. , 1960 .

[4]  C. Biliaderis,et al.  Physical properties of starch nanocrystal-reinforced pullulan films , 2007 .

[5]  D. Thomson,et al.  Characterization of the surface morphology of durum wheat starch granules using atomic force microscopy , 2008, Microscopy research and technique.

[6]  M. Parker,et al.  In situ Imaging of Pea Starch in Seeds , 2008 .

[7]  J. Couch,et al.  Buckwheat as a source of rutin. , 1946, Science.

[8]  F. Krok,et al.  Characterization of starch nanoparticles , 2009 .

[9]  P. Chang,et al.  Starch-based nanocomposites reinforced with flax cellulose nanocrystals , 2008 .

[10]  K. Huber,et al.  Visualization of Channels and Cavities of Corn and Sorghum Starch Granules , 1997 .

[11]  E. Shimoni.  Starch as an encapsulation material to control digestion rate in the delivery of active food components. , 2008 .

[12]  T. Sunarti,et al.  Starches from different botanical sources I: Contribution of amylopectin fine structure to thermal properties and enzyme digestibility , 2005 .

[13]  P. Calvert.  Biopolymers: The structure of starch , 1997, Nature.

[14]  José Miguel Aguilera,et al.  Microstructural principles of food processing and engineering , 1999 .

[15]  M. Miles,et al.  Internal structure of the starch granule revealed by AFM. , 2001, Carbohydrate research.

[16]  I. Suda,et al.  Relationships between chain length distribution of amylopectin and gelatinization properties within the same botanical origin for sweet potato and buckwheat , 1998 .

[17]  J. Fornal,et al.  Characteristics of Buckwheat Grain Starch and the Effect of Hydrothermal Processing upon its Chemical Composition, Properties and Structure , 1984 .

[18]  P. Colonna,et al.  Order in maize mutant starches revealed by mild acid hydrolysis , 2002 .

[19]  L. Juszczak,et al.  Non-contact Atomic Force Microscopy of Starch Granules Surface. Part I. Potato and Tapioca Starches , 2003 .

[20]  Julien Bras,et al.  Starch nanoparticles: a review. , 2010, Biomacromolecules.

[21]  B. Raj,et al.  Moisture‐sorption characteristics of starch/low‐density polyethylene films , 2002 .

[22]  C. Gaines,et al.  Granule Size Distribution and Chemical Composition of Starches from 12 Soft Wheat Cultivars , 1998 .

[23]  S. Ball,et al.  Recent progress toward understanding biosynthesis of the amylopectin crystal. , 2000, Plant physiology.

[24]  V. J. Morris,et al.  Using AFM to image the internal structure of starch granules , 2002 .

[25]  A. Dufresne,et al.  The molecular structure of waxy maize starch nanocrystals. , 2009, Carbohydrate research.

[26]  M. Parker,et al.  Atomic force microscopy of pea starch: origins of image contrast. , 2004, Biomacromolecules.

[27]  A. Eliasson,et al.  The influence of amylose and amylopectin characteristics on gelatinization and retrogradation properties of different starches , 1998 .

[28]  F. Krok,et al.  Deep-freezing of potato starch. , 2000, International journal of biological macromolecules.

[29]  P. Chang,et al.  Analytical, Biochemical and Physicochemical Aspects of Starch Granule Size, with Emphasis on Small Granule Starches: A Review , 2004 .

[30]  A. W. Robards,et al.  The events leading to the formation of ghost remnants from the starch granule surface and the contribution of the granule surface to the gelatinization endotherm , 1998 .

[31]  Y. Takeda,et al.  Physicochemical properties and structure of large, medium and small granule starches in fractions of normal barley endosperm. , 2001, Carbohydrate research.

[32]  M. Davies,et al.  High Resolution Imaging of Starch Granule Surfaces by Atomic Force Microscopy , 1998 .