摘要:

AbstractVarious physico‐chemical properties of starches isolated from 21 Australian wheat varieties were assessed. Molecular weights varied between the starches and were lower in those from soft wheats. Proportions of small granules were significantly correlated with starch amylose and protein contents; those of large granules correlated negatively with fat content. Granule crystallinity was correlated with hardness of the parent wheats. Gelatinisation temperatures, measured by differential scanning calorimetry, varied between the starches within the range of 46–79°C. Enthalpies of gelatinisation, 4.6–13.3 J/g of dry starch, were correlated with both amylopectin content and wheat hardness. Minimum moisture for gelatinisation, 0.15–0.56 wa‐ter/g of dry starch, was significantly correlated with both amylose and fat contents of

ISSN:0038-9056    

DOI:10.1002/star.19930450902

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractStarches of six diploid Ipomoea trifida (H. B. K.) DON. clonal strains were examined. Granule size, granule traits obtained by scanning electron microscopy (SEM), X‐ray diffraction patterns and differential scanning calorimetry (DSC) parameters of starches of the diploid strains were compared with those of two sweet potato cultivars. The granule sizes of the diploids were definitely smaller than those of cultivars. SEM showed that starches of the diploid strains were composed of predominantly angular granules having crater‐like impressions. Starches of both the diploids and the cultivars showed typical X‐ray diffraction patterns (C type) with diffuse maximum peak around 18.5° 26, but in the case of diploid strain “H3–28”, distinctive sharp peaks suggesting some differences in crystal structure were observed. DSC parameters, namely, onset temperature (To), peak temperature (Tp), conclusion temperature (Tc) and enthalpy of gelatinization (Δ) obtained from starch‐water mixtures (ratio 1:3) were higher in the diploid starches compared to those of the two cultivars. Significant correlation coefficients were found between the gelatinization parameters and mean granule diameter of the s

ISSN:0038-9056    

DOI:10.1002/star.19930450903

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe xylose isomerase of Streptomyces coelicolor A3 (2) was purified by conventional techniques to apparent homogeneity. The relative molecular mass of the sub‐unit of the enzyme was determined as 40kDa and the enzyme is composed of 4 such sub‐units. Significantly, the enzyme is optimally active at pH 7.0 and at 70°C, and requires only magnesium as cofactor. Presence of magnesium considerably minimizes inhibition of the enzyme by calcium. These considerations suggest that the present enzyme is more ideal for application in high fructose syrup process. The enzyme has Km = 0.041 M for xylose and 0.2 M for glucose with the corresponding Vmaxvalues being 58.4 and 9.09 mol. min−1mg−1. Among the various amino acid modifying reagents, acetic anhydride and ethyl dimethyl amino propyl carbodiimide showed the most pronounced effects of reduction and enhancement of catalysis resp

ISSN:0038-9056    

DOI:10.1002/star.19930450904

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractWe examined cereals and legume starches with different amylose contents, using X‐ray wide‐angle scattering. The parts of polymorphs in the crystalline regions and the crystallinity of the starches were determined. The high‐amylose starches hold 74.6%‐84.6% B‐type and 15.4%‐22.6% VH‐type.Crystallinity of high‐amylose starches is xc = 0.154–0.17. According to phase analysis of the scattering curve of wheat starch 6.8% B‐type and 93.2% A‐type are contained. Thus, in the crystalline phase wheat starch is more heterogeneous than maize starch. The residuary substance of heterogeneous hydrolysis of wheat starch at T1 =58°C is an insoluble sediment, which does contain already 17.1 % VH‐Amylose. This is the proof of the amylose‐lipid complex in the sediment. If the temperature of hydrolysis raised to 70°C, the VH,‐amylose proportion increased to 80.5%. Since the crystalline VH‐ structures are detectable during heterogeneous hydrolysis as from T1 = 58°C, they seem to have co

ISSN:0038-9056    

DOI:10.1002/star.19930450905

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractSynthetische Kunststoffe wurden unter Verwendung von Stärken modifiziert und neue Verbundwerkstoffe entwickelt, deren resultierende Eigenschaftsprofile Anwendungen zulassen, die dem Ausgangspolymeren verschlossen bleiben. Drei unterschiedliche Kategorien von Verbundwerkstoffen wurden auf einem gleichsinnig drehenden, dicht kämmenden Doppelschneckenextruder hergestellt und hinsichtlich ihrer physikalischen und mechanischen Eigenschaften charakterisiert. Die erste Kategorie umfaßt Werkstoffe, bei denen die Stärke in ihrer natürlichen granulären Erscheinungsform als funktioneller Füllstoff genutzt wird. Das Eigenschaftsprofil hängt dabei ent‐scheidend von den Wechselwirkungen zwischen Stärkekornoberfläche und Matrixpolymer ab, und kann durch ein Organosilancoating der Stärke signifikant verbessert werden. Die anderen beiden Kategorien basieren auf der Verwendung von destrukturierter Stärke, die durch mechanisch/thermische Desintegration der makroskopischen Stärkekörner unter Zugabe von Plastifikatoren und Weichmachern im Extruder erzeugt wird. Die so erzeugte entstandene, thermoplastisch verarbeitbare Formmasse kann im Einzelfall direkt als Werkstoff Verwendung finden. Der bedeutendere Anwendungsbereich für thermoplastische Stärken (TPS) ergibt sich jedoch im Verbund mit Polymeren in Form von Legierungen und Blends. In Kombination mit Ethylencopolymeren entstehen Verbundwerkstoffe, bei denen die TPS trotz ihres höheren Anteils in Form kleinster, diskret verteilter Partikeln in der, die kontinuierliche Phase bildenden Polymermatrix eingelagert ist. Die resultierenden Eigenschaften solcher Blends hängen dabei entscheidend von der sich ausbildenden Mikrostruktur

ISSN:0038-9056    

DOI:10.1002/star.19930450906

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19930450907

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19930450908

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19930450909

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19930450910

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19930450911

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY