原子力显微镜在淀粉颗粒结构研究中的应用

本文首先介绍了原子力显微镜的基本原理，硬件结构和工作模式，其次将原子力显微镜在淀粉颗粒结构研究中的应用做了一个简要的综述。利用原子力显微镜观察淀粉颗粒表面和内部的精细结构，对比较不同植物学来源的淀粉和在淀粉颗粒结构上考察基因突变对淀粉的影响，以及在淀粉糊化或贮藏的回生阶段追踪淀粉颗粒结构的变化都具有十分重要的辅助意义。     

Pasting and rheologic properties of potato starch and maize starch mixtures

This study characterized the pasting and rheologic behavior of potato/maize starch mixtures of various ratios. Pasting analysis using a Brabender Viscograph indicated that most important pasting parameters did not show a linear change that reflected the ratio of starches. A significant effect on final viscosities and setback was evident. The diameter distribution of starch granules that were heated to 70°C was determined by a laser particle size analyzer. The result suggested that the swelling of starch granules in the mixtures was reduced at the onset of gelatinization. Measurement of dynamic viscoelasticity measurement demonstrated that the mixtures showed slightly higher loss modulus than those seen for the control at small measuring frequencies. The mixture pastes with a high proportion of potato starch exhibited more pseudoplasticity and had a more significant thickening effect than either control paste. Nonadditive behavior was found by mixing potato and maize starch. This suggests that an appropriate blend of starches from diverse botanical origins may provide a simple practical avenue for manipulation.     

Effect of endosperm type on texture and in vitro starch digestibility of maize tortillas

Tortilla is the main staple of Mexico and it is made using diverse maize varieties, which have different endosperm types. Three maize varieties with vitreous, intermediate and floury endosperms were used. Texture and starch digestibility were evaluated in freshly prepared and stored tortillas for 24, 48 and 72 h. Tortilla made with maize of vitreous endosperm had the highest force to rupture and the lowest distance of elongation, indicating more rigid texture. Stored tortillas had lower available starch content and higher effect was shown by tortilla of vitreous endosperm, pattern that agrees with the higher increase in the resistant starch content with the storage time. Fresh tortilla of floury endosperm showed the highest hydrolysis rate during the first 15 min followed by tortillas of intermediate and vitreous endosperms. Starch hydrolysis values decreased when storage time increased, in agreement with the resistant starch content in the stored tortillas. At the longest storage time (72 h) tortilla of floury endosperm presented higher hydrolysis rate, followed by tortilla of intermediate and vitreous endosperms. The endosperm type plays an important role in the textural and starch digestibility of fresh and stored tortillas.     

The effect of ball milling treatment on structure and porosity of maize starch granule

Maize starch was mechanically treated by a planetary ball mill at 500 rpm for 1, 2 and 3 h. The effect of ball-milling treatment on structure and porosity of maize starch granule was studied. The SEM and TEM analyses indicated that starch granule surfaces were significantly changed and cavities in the central region of distorted granules were observed in the company with disappearance of alternate growth rings. The FT-IR analysis showed that ball milling treatment significantly increased the intensity of band 3382 cm⁻¹ and decreased the ratio of 1047/1018 cm⁻¹ and 995/1018 cm⁻¹ corresponding to the crystalline/amorphous part of starch structure. Special surface area (S_BET), cumulative volume (V_BJH), average diameter pores (D_BJH), span and median diameter (D_{v, 0.5}) increased rapidly and then decreased gradually. The XRD patterns, FT-IR and ¹³C CP/MAS NMR spectra showed that the crystallinity of starches and content of double helices of starch chains were decreased, respectively.

Industrial relevance

Ball milling is one kind of physical modified method in polymer industry. It can be used in a variety of applications, including nanomatrix composites, dispersed alloy materials, metallic refinery, ore treatment, waste disposal, and synthesis of organic materials. Starch is a natural carbohydrate polymer, it contributes greatly to the textural properties of many foods and is widely used in food and industrial applications as a thickener, colloidal stabilizer, gelling agent, bulking agent and water retention agent. However, limitations such as low solubility, high viscosity, shear resistance, thermal resistance, thermal decomposition and high tendency toward retrogradation limit its use in some food and non-food systems.After ball milling treatment, the reactivity of starch is increased. Furthermore, milled starches exhibit the adsorptive capacity which can offer new opportunity for starch application, for example as sorbent in food or pharmaceutical.     

In situ examination of starch granule-soy protein and wheat protein interactions

The objective of this study was to evaluate the association between heat and pressure-treated soy proteins and wheat prime starch relative to the level of granule surface proteins present. Soy isolates were manufactured from defatted soy flour and from two types of textured soy flour. Conditions for binding between wheat starch and soy fractions were established by altering pH, protein and sucrose concentrations. Conformations of exogenous proteins bound to the wheat starch granule surface were evaluated using an amyloglucosidase assay. Proteins present on the granule surface were removed and soy protein binding was reevaluated. Thermal and pressure processing of soy protein significantly influenced binding kinetics. Textured soy proteins exhibited increased wheat starch granule adsorption characteristics compared to untreated soy protein. Removal of native wheat starch granule surface proteins decreased the binding of added proteins. This suggests that native granule proteins may mediate the binding of exogenous protein.     

Visualisation of starch granule morphologies using confocal scanning laser microscopy (CSLM)

Confocal scanning laser microscopy (CSLM) is a powerful tool for the visualisation of starch granules from their botanical source, during processing into their final application. CSLM allows the visualisation of the starch gelatinisation process and of granule remnants in starch pastes in their original environment and without modification. In this study, CSLM has been used to study the granule morphology of starch from different botanical sources. CSLM is a suitable technique to obtain, under mild conditions, 2D and 3D images of the granules. The samples for observation by CSLM do not require complicated preparations such as drying and metal coating as in the case of electron microscopy. Moreover, the CSLM technique is not limited to the observation of native starch granules, as the gelatinisation process and the remnants of granules in starch pastes can be monitored in their original environment. In this way, starch granules can be visualised from their botanical sources to the final application with a single microscopic technique. © 2002 Society of Chemical Industry     

糯玉米淀粉及其改性淀粉在食品工业中的应用

介绍了糯玉米淀粉及其变性淀粉在制糖、酿造、食品、粘合剂生产等方面的应用。     

Characterisation of starch quality from barley varieties grown in South Africa

Starch is a major determinant of grain quality in cereals but the variation in starch structure has yet to be fully explored in its relation to processing impacts. This study examined the starch properties of South African grown malting barley varieties. Starch amounts, amylose content, covalently bound phosphate, starch granule size, starch molecular structure and pasting properties were examined. There was no difference in amylose content but there was variation in the amylose chain length distribution, despite all barleys showing similar granule parameters. The longer amylose chain length resulted in increased pasting temperature. There was no difference in phosphate content for these samples. Starch properties for the brewing industry are important in the context of the production of fermentable sugars. The variation in starch structure was not observed when measuring content and could impact on fermentation efficiency through variation in fermentable sugars hydrolysed from the starch.     

Microstructures of starch granule,starch digestibilities and predicted glycaemic index of common bean mutants in Taiwan

In this study, the microstructure of starch granule and in vitro starch digestibility were compared in de‐coated seeds of common bean variety Hwachia and its NaN₃‐induced mutants. Significant differences in starch granule size (between 17.92 and 27.00 μm), total starch content (between 436.5 and 456.8 mg per seed) and resistant starch content (between 51.6 and 203.3 mg per seed) were found among mutants. Both boiling and autoclaving decreased resistant starch content in processed common beans. Significant difference in predicted gylcaemic index (pGI) (between 48.82 and 64.55%) for processed beans also existed among mutants. However, 96 h of 4 °C storage increased resistant starch content in processed common beans, possibly resulted from starch retrogradation during storage. Mutants SA‐05, SA‐08 and SA‐31, which have smaller seed weight and lower pGI (average of 50.08%) compared to Hwachia (pGI of 57.05%), can be used to produce common bean based low GI dietary carbohydrate.     

追氮对夏玉米淀粉含量及其糊化特性的影响

以郑单958为材料,研究玉米随追氮量增加玉米籽粒淀粉含量、淀粉相关酶活性及其淀粉糊化特性的影响,研究结果表明玉米籽粒淀粉及直链淀粉含量随追氮量的增加先升高后略有下降;腺苷二磷酸葡萄糖焦磷酸化酶(ADPG-PPase)、尿苷二磷酸葡萄糖焦磷酸化酶(UDPG-PPase)及束缚态淀粉合成酶(GBSS)的活性随追氮量的增加先升高后降低。可溶性淀粉合成酶(SSS)的活性随追氮量的增加先降低后升高;随追氮量的增加淀粉的峰值黏度、低谷黏度、最终黏度及崩解值先升高后降低,峰值时间以及糊化温度先降低后升高。     

The importance of amylose and amylopectin fine structures for starch digestibility in cooked rice grains

Statistically and causally meaningful relationships are established between starch molecular structures (obtained by size-exclusion chromatography, proton NMR and multiple-angle laser light scattering) and digestibility of cooked rice grains (measured by in vitro digestion). Significant correlations are observed between starch digestion rate and molecular structural characteristics, including fine structures of the distributions of branch (chain) lengths in both amylose and amylopectin. The in vitro digestion rate tends to increase with longer amylose branches and smaller ratios of long amylopectin and long amylose branches to short amylopectin branches, although the statistical analyses show that further data are needed to establish this unambiguously. These new relationships between fine starch structural features and digestibility of cooked rice grains are mechanistically reasonable, but suggestive rather than statistically definitive.     

Morphological,thermal, rheological and retrogradation properties of potato starch fractions varying in granule size

The physicochemical properties of small, medium and large starch granules separated from four potato cultivars were investigated to reveal whether functional properties differed among the various size classes of the starches. Large‐size fractions showed higher amylose content and light transmittance and lower swelling power than small‐size fractions. The granules from the three fractions had diameters of 5–20, 25–40 and 40–85 µm respectively. The large and medium granules were ellipsoidal to irregular or cuboidal while the small granules were spherical or ellipsoidal in shape. The transition temperatures and gelatinisation temperature range of the fractionated starches increased while the enthalpy of gelatinisation decreased with decreasing granule size. Rheological parameters such as peak storage (G′) and loss (G″) moduli increased in the order small‐, medium‐ and large‐granule starches when subjected to temperature sweep testing. The breakdown in peak G′ during the heating cycle and retrogradation during storage were found to be highest for large‐ and lowest for small‐size fractions. The differences in functional properties among the different size fractions suggested that the granule size distribution is an important parameter that can influence the behaviour of potato starch during processing. Copyright © 2004 Society of Chemical Industry     

Microbial degradation of normal maize and bm3 maize in the rumen observed by scanning electron microscopy

Samples of internodes and leaf blades from normal and bm3 maize (Zea mays L) harvested at dough to glazing stage were studied separately to determine their dry matter content, wall composition (NDF, ADF and ADL) and digestibility in sacco. For examination by light and scanning electron microscope, fragments 0·5 cm long were cut halfway along the internode beneath the female ear and on the corresponding blade. The wall and lignin contents of the bm3 maize were lower than in normal maize. The bm3 maize had a greater extent and faster rate of internode and blade disappearance in the rumen than normal maize samples. The histological structure of the two maizes was the same, but after 24 h in the rumen the parenchyma of the bm3 maize had degraded faster and the secondary walls of the fibres of its vascular bundles were degraded whereas those of normal maize had remained intact. After 72 h in the rumen the sclerenchyma of normal maize had changed little whereas that of the bm3 maize had much thinner walls and was abundantly colonised by rumen bacteria.     

Determination of structural changes in microwaved rice starch using Fourier transform infrared and Raman spectroscopy

FTIR and confocal laser micro‐Raman spectroscopy methods were used to investigate the differences in chemical bond types, bond energy, and skeleton connection system between rice starch heated in a microwave and rice starch heated rapidly using a traditional method. The temperature of the peak absorption position of C H mode vibration of microwaved sample was lower and the temperature of peak position of C O related mode vibration on skeleton of microwaved sample were higher than those of the rapid heating sample, but there were no changes to other skeletal mode vibrations such as glycosidic linkage and pyranose ring. Overall, microwave‐heat treatment did not change the type of chemical groups in starch molecules, and induce the formation of new chemical group bonds, or change the way that they interact with each other in rice starch. Furthermore, the vibrational energy of the chemical‐bond of microwave‐treated rice starch changes gradually during the heating process.