Effects Of Lipids And Granule Associated Proteins On Structural And Physicochemical Properties Of A, B-Wheat Starch

Lipids and granule associated proteins within starch granules have great effects on its physiochemical and structural properties. A, B-wheat starch isolated from normal(cv, Xinong 979 and Yumai 49-198) and waxy wheat grains were performend de-fat, de-protein and de-fat plus de-protein treatment, and the effects on starch chemical composition, morphological structure and physiochemical properties were compared with untreated granules. The effect mechanisms of lipids and granule associated proteins on physicochemical properties and structural properties of A- and B-starch were also investigated. The main conclusions are concluded as following:(1) Wheat starch granules are composed of large A- and small B-starch. A-granule starch exhibited smooth elliptical or spherical, while B-granule presented the agglomeration polygonal or irregular spherical, and its number is much more than the A-granule. Both Aand B-wheat starch presented typical A-type crystalline, and starch granule possessed internal cavity, channel and growth ring structure. The relative crystallinity degree, and the clarity of polarization cross and growth ring of A-starch remain superior to B-starch granules. A-starch isolated from normal wheat had higher apparent amylose content and total amylose content than B-granule starch.The transparency of normal A- and B-wheat starch was significantly decreased with the extension of storage time, while waxy A- and B-wheat starch was increased with increasing of storage time. The retrogradation rate of normal A-granule was faster than B-granule, while no retrogradation occurred phenomenon the for waxy A- and B-starch. Both solubility and swelling power of A, B-wheat starch increased with the temperature risen. A-starch had higher onset and peak temperature, and higher peak, trough, final and setback viscosity, and enthalpy value compared to B-granule, while B-granule starch had a higher peak time than A-starch. Waxy A, B-starch had a higher peak viscosity, breakdown, heat enthalpy value and a lower pasting temperature, peak time, setback than normal A, B-granule.(2) The de-fat treatment had no significant effects on morphology, polarization cross, crystal type, pasting temperature, peak time, solubility, swelling power, onset temperature, peak temperature, final temperature and heat enthalpy value on norml and waxy A, B-wheat starch. Whereas, de-fatted norml and waxy A, B-granule exhibited higher transparency and higher peak, trough and final viscosity, and smoother surface and a more distinctbirefringence, and a lower relative crystallinity, retrogradation volume and syneresis compared to untreated samples.(3) The deproteinized A- and B-granule exhibited a higher relative crystallinity, peak viscosity, breakdown, setback, transparency, retrogradation volume, syneresis, swelling power, onset temperature, peak temperature and final temperature, a more distinct birefringence, while preaented a lower trough viscosity and freeze-thaw stability compared to untreated granules. No significant effects were found on polarization cross, crystal type and enthalpy value after de-protein treatment. Furthermore, a obviously depression phenomenon could be found in the center of deproteinized A- and B-granule surface. A decreased pasting temperature peak time value, and a increased solubility value were found in deproteinized normal wheat starches, while the deproteinized waxy starch showed an opposite tendency in pasting temperature, peak time and solubility value.(4) The defat plus deprotein treatment had no influences in morphology, polarization cross, crystal type and heat enthalpy value of A- and B-starches. However, defat plus deprotein treatment caused a higher peak viscosity, setback, breakdown, transparency, retrogradation volume, syneresis, onset temperature, peak temperature, final temperature, and smoother surface and more distinct birefringence, while caused a lower relative crystallinity. Moreover, the pasting temperature, peak time and solubility of defatted plus deproteinized starches exhibited a similar tendency with after the de-protein treatment.