三偏磷酸钠交联马铃薯淀粉颗粒膨胀历程及溶胀机理研究

本文利用淀粉与三偏磷酸钠的交联反应，通过控制交联反应程度，成功地控制了交联淀粉颗粒地膨胀并使其停留在不同的溶胀阶段，详细地研究了处在不同溶胀阶段交联淀粉颗粒的结构特征和变化趋势，揭示了交联淀粉颗粒由高交联非糊化到低交联溶胀糊化具体地膨胀历程及溶胀机理，即交联马铃薯淀粉是以颗粒尾端为主的不均衡膨胀。     

三氯氧磷交联木薯淀粉颗粒膨胀历程及溶胀机理研究

利用木薯淀粉与三氯氧磷的交联反应,通过控制交联反应程度,成功地控制了交联淀粉颗粒的膨胀并使其停留在不同的溶胀阶段,详细地研究了处在不同溶胀阶段的三氯氧磷交联木薯淀粉颗粒的结构特征和变化趋势,揭示了三氯氧磷交联木薯淀粉颗粒的具体的膨胀历程及溶胀机理,即木薯淀粉是“花蕾绽放式”膨胀历程。     

三偏磷酸钠交联玉米淀粉颗粒膨胀历程及结构特征

利用淀粉与三偏磷酸钠的交联反应,通过控制交联反应程度,成功地控制了交联淀粉颗粒膨胀程度并使其停留在不同的溶胀阶段,详细研究了处在不同溶胀阶段交联淀粉颗粒的结构特征和变化趋势,揭示了三偏磷酸钠交联玉米淀粉颗粒的膨胀历程及结构特征,即随着淀粉颗粒交联程度的降低,颗粒的膨胀历程由中心脐点处爆裂膨胀方式转化为颗粒整体向外的均匀膨胀方式.     

三偏磷酸钠高交联马铃薯淀粉非糊化特征研究

研究了以三偏磷酸钠为交联剂制备非糊化的高交联马铃薯淀粉的方法;测定了反应的取代度和布拉班德粘度曲线,提出高交联马铃薯淀粉与原淀粉颗粒不同,在沸水中只发生轻微溶胀,呈非糊化颗粒态。     

三偏磷酸钠高交联玉米淀粉非糊化特征研究

研究了以三偏磷酸钠为交联剂制备非糊化的高交联玉米淀粉的方法，测定了反应的取代度和布拉班德粘度曲线，提出高交联玉米淀粉与原淀粉颗粒不同，在沸水只发生轻微溶胀，呈非糊化颗粒态。     

高交联木薯淀粉非糊化特征研究

研究了以三偏磷酸钠为交联剂制备非糊化的高交联木薯淀粉的方法,测定了反应的取代度和布拉班德粘度曲线,提出高交联木薯淀粉与原淀粉颗粒不同,在沸水中只发生轻微溶胀,呈非糊化颗粒态。     

高交联木薯淀粉的非糊化特性

以三氯氧磷为交联剂制备非糊化的高交联木薯淀粉,并测定了反应的取代度和布拉班德粘度曲线,研究了在沸水中受热后非糊化淀粉的颗粒形貌及粒度分布等特性．提出高交联非糊化木薯淀粉存在着不同于原淀粉颗粒的在沸水中只发生轻度有限溶胀的非糊化颗粒态     

高交联马铃薯淀粉非糊化特性研究

研究了以三氯氧磷为交联剂制备非糊化的高交联马铃薯淀粉的方法，测定了反应的取代度和布拉班德粘度曲线，研究了在沸水中受热后非糊化淀粉的颗粒形貌及粒度分布等特性。提出高交联非糊化马铃薯淀粉存在着不同于原淀粉颗粒的沸水中只发生轻度有限溶胀的非糊化颗粒态。     

醚化、交联对玉米淀粉功能性质的影响

本文研究了醚化和交联反应对玉米淀粉物理性质和结构的影响。实验结果表明:醚化明显地改善了淀粉糊的透明度和低温稳定性,降低了糊化温度;醚化淀粉再经交联后,可改善淀粉糊的粘度稳定性。醚化及交联反应主要在淀粉的非结晶区进行,反应并未破坏淀粉颗粒。醚化影响直链淀粉的构象并在颗粒表面形成空穴,交联则使淀粉颗粒在蒸煮后仍保持完整并抑制了直链淀粉的渗出。     

淀粉颗粒粒径对淀粉交联程度影响的研究

本文通过改变淀粉颗粒的粒径来研究淀粉的交联。交联程度高的淀粉,溶胀度低,在同温度下黏度低。通过测定交联淀粉的黏度与溶胀度发现:淀粉的交联难易程度的大小随着淀粉颗粒粒径的变化而变化,在一定范围内,淀粉颗粒粒径越大,淀粉越易发生交联反应,同一交联条件下越易形成交联程度高的淀粉。     

Physicochemical and Morphological Characteristics of Nixtamalized Maize Starch

The effect of nixtamalization on physicochemical and morphological characteristics of starch was studied. Determination of total starch, ash and amylose content, of swelling and solubility, gelatinization characteristics and morphological studies were carried out in starch isolated from native (S) and nixtamalized (NS) maize flours. Thermal analysis showed that nixtamalization produced starch annealing due to the higher gelatinization temperature obtained for NS. However, S had slightly lower enthalpy values. The swelling profile was similar for both starches, but the solubility values at the temperatures assessed were slightly higher in the NS samples. At temperatures below gelatinization, the granules showed the Maltese cross while at higher temperatures only ghost of granules were observed. The nixtamalized starch had larger granule sizes than the native starch, due to the partial swelling produced in the heating during the nixtamalization process. Larger granule sizes were also observed by image analysis, because major axis and area parameters were higher in NS samples than in S samples. The nixtamalization process produced changes in chemical, thermal and morphological characteristics, becoming important in products obtained from nixtamalized maize.     

Aggregate Formation and Segregation of Maize Starch Granules Cooked at Reduced Moisture Conditions

The mechanism of formation of aggregates of maize starch granules was studied through the kinetics of their destruction. The cooking of the starch, which was done with limited amount of water (1:1) to imitate the conditions of starch foods, induced the formation of aggregates of different sizes. These were dispersed in ethanol and agitated for different periods, provoking their desegregation. The size distribution and its dependence on time was measured by means of laser light scattering. It was found that the aggregates are built in a fractal‐type geometry: a group of starch granules conform a small aggregate, then groups of the latter build into larger ones, and so on, observing up to five scales, depending on the cooking degree. The aggregates are held together by gelatinized granules that show no Maltese cross. The formation of the aggregate classes can be explained by granules swelling ramdomly at different points of the sample, with a lower probability of dual gelatinization of neighbor granules.     

Comparative Characterisation of Aqueous Starch Dispersions by Light Microscopy,Rheometry and Iodine Binding Behaviour

Aqueous potato, wheat and pea starch dispersions (2 g dry Starch/100 g dispersion) were prepared at different time-temperature conditions and characterised by light microscopy of stained cryo-sections, amperometric iodine titration and rheometry. Depending on the gelatinisation conditions and the type of starch, a broad range of microstructures was obtained ranging from limited swelling to complete disintegration of starch granules. The swelling was accompanied by leaching of amylose from the granules and accumulation of amylose in the centre of the granules. The iodine binding capacity of the starch systems was related to the extent of swelling and solubilisation of starch and is therefore an appropriate indicator to follow the gelatinisation process. The flow behaviour was also sensitive to differences in the microstructure. The combination of light microscopy, iodometry and rheology successfully allowed the extensive characterisation of the supramolecular structure of low concentration starch systems.     

Milling of rice grains: The roles of starch structures in the solubility and swelling properties of rice flour

Rice flours with different particle sizes and degrees of damaged starch granules were produced by hammer milling and cryogenic milling of rice grains, where degradation of starch molecules was evident in the hammer‐milled flours, but not in the cryogenically milled flours. The solubility and swelling properties of the resulting rice flours were determined in cold (30°C) and hot water (90°C). The cold‐ and hot‐water starch solubility was strongly correlated with the degree of damaged starch granules, and weakly with the particle size of rice flour. No evident correlations were observed between starch solubility and the molecular structures, indicating that molecular degradation by milling process was not the only precondition of increased starch solubility. Possible mechanism for the observed correlations is that increasing surface area and/or exposure of loosely packed inner part of starch granules with increasing degree of damaged starch granules allowed more starch molecules to leach out in cold and hot water. Furthermore, the cold‐water swelling of rice flour was strongly correlated with the degree of damaged starch granules, possibly due to the rapid hydration of damaged starch granules, whereas the hot‐water swelling did not show any correlations with flour particle size and granular and molecular starch structures. The results have provided better insights in the relationship between starch structures and solubility and swelling properties of rice flour, which can be used to improve the manufacture and selection criteria of rice flour for better products.     

Swelling Characteristics of Native and Chemically Modified Wheat Starches as a Function of Heating Temperature and Time

The effects of hydroxypropylation (molar substitution, MS 0.05, 0.12, and 0.18) and cross‐linking (0.03%, 0.1%, and 0.2%) on swelling properties of wheat starch granules at several temperatures and heating times were investigated by laser diffraction particle size analysis. Starch samples were dispersed in water at temperatures ranging from 30 to 90°C, for 1 to 360 min. All starch granules exhibited distinct bimodal size distributions: small B‐granules with mean diameter of 2.3 μm and large A‐granules with mean diameter of 20.4 μm. As temperature increased, the B‐granules swelled more than A‐granules. Swelling of A‐granules sharply increased at 60°C. Swelling was more pronounced with increasing molar substitution of hydroxypropyl groups, while increased swelling was not observed in cross‐linked starches. The dependence of swelling capacity on heating time was different at 60 and 80°C as well as amongst modified starches. As heating time was prolonged, mean granule sizes for native, control, and hydroxypropylated starches at 80°C decreased after reaching maximum size due to loss of granule integrity, while those at 60°C showed no significant change.     

Changes in Starch Granules Trapped and Heated Using Optical Tweezers

A microscopic method to investigate the swelling process of individual starch granules heated in excess water is proposed. A starch granule focused under a light microscope is adjustably trapped using the optical tweezing of a near-infrared laser beam, which simultaneously heats the granule. Using this method, morphological changes in starch granules during heating were continuously recorded and quantitatively analyzed by image-processing techniques. The changes in granules of domestic wheat starches with differing amylose content were investigated under irradiation by the laser beam at constant optical power. The shapes of swollen granules of waxy wheat starches were observed to be distinctly different from those of non-waxy starches. Numerical indicators, specifically the time constant of swelling for the granule and its swelling magnification, were also obtained. These showed little relation to the pasting profiles of the same starches, obtained with a Rapid Visco Analyser.