摘要:

AbstractPotato starch was oxidized with a neutral aqueous bromine solution at seven different levels of molar ratios of bromine/starch (1/40–5/1). The molecular weight distribution of the products obtained was analysed by gel permeation chromatography on two different agarose gels, Sepharose CL‐2B and Superose 6. A gradually increased fragmentation of the molecules with increased oxidation level was noticed. Some of the modified samples were debranched and the products obtained were analysed by gel permeation chromatography. For comparison amylose and waxy maize starch were also treated at the 1/20 and 1/5 molar ratios. The results indicate that the amylose is more easily degraded to small fragments than amylopectin during the oxidation process. An enzymatic starch analysis method was applied on the oxidized samples. This method was found suitable for estimating the total content of introduced keto and carboxylic groups into the modified prod

ISSN:0038-9056    

DOI:10.1002/star.19900421102

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractNative potato starch and potato starch oxidised with bromine at different concentrations were studied. A successive decrease of the gelatinisation enthalpy and a downward shift in the gelatinisation temperature were observed by the use of differential scanning calorimetry. When the oxidation was followed by a reduction step, those effects were accentuated. The mean molecular weight of the starch diminshed as the concentration of bromine oxidant was increased. In accordance with this, the viscosity of water solutions of corresponding samples successively decreased. However, when samples were reduced after the oxidation step, an increase in the viscosity was observed. A microscopic investigation showed that the granule structure was lost already at the lowest level of oxidation.

ISSN:0038-9056    

DOI:10.1002/star.19900421103

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe combined effect of oxidation and etherification on the molecular structure of starch was investigated. Maize and rice starches were used. Oxidation was effected using sodium hypochlorite while etherification was performed by reacting starch with acrylamide in presence of sodium hydroxide; this reaction is known as carbamoylethylation. The extent of the latter, expressed as % N, was found to increase by decreasing the molecular size of starch through oxidation. The carbamoylethyl starches so obtained could be precipitated by ethanol and they are soluble in water irrespective of the kind of starch. On the other hand, results of rheological properties indicated that they are governed mainly by the molecular size of starch. Oxidized starches with relatively high molecular size exhibit thixotropic behaviour. The degree of thixotropy decreases and changes into pseudoplasticity as the molecular size of starch decreases. The results also indicated that at constant rate of shear the apparent viscosity of carbamoylethyl starches decreases as the molecular size decreases. Furthermore, the rheological properties of carbamoylethyl starch pastes undergo considerable changes and so does the apparent viscosity when these pastes were stored for 3 days.

ISSN:0038-9056    

DOI:10.1002/star.19900421104

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe hydroxyethylation of potato starch was studied in a gas‐solid system. The rate of diffusion of ethylene oxide into the granules, the solubility of ethylene oxide in native starch and the rate of reaction between gaseous ethylene oxide and alkaline starch powder were measured. The partial pressure of ethylene oxide was kept at a constant value close to atmospheric pressure, the temperature was varied between 303 and 323 K.The ratio of the ethylene oxide concentrations in the starch granules and in the gas phase. mEO, is almost independent of the water content of the granules. The dependence ofEOon temperature can be described with theVan 't Hoffequation: mEO= 5.93 · 10−5exp (33390/RT). The rate of diffusion of ethylene oxide in the granules with a narrow size distribution does not followFick's law but it can be described with relaxation controlled diffusion (Case II diffusion). The parameter u of this model, the front velocity, appears to depend on the persentage moisture W, present in the gran

ISSN:0038-9056    

DOI:10.1002/star.19900421105

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractInvestigations of the potato starch hydrolysis during bacterial α‐amylase “BAN 240 L” liquefaction to 19.5 DE and then saccharification with exo‐acting α‐amylase “Maltogenase 1000 L” alone and together with pullulanase “Promozyme 200 L”, were carried out. Under adequate conditions at different enzyme dosages hydrolyzates of the maltose, content of 60 to about 80% in DS at significantly lower glucose and minimal maltotriose content were obtained. Investigations comprised both carbohydrate contents in hydrolyzates, changing with hydrolyse course and dextrin molecular structure in hydrolyzates. It was found that decreasing dextrin molecular weight and the number of branchings in dextrin molecules was accompanied by characteristic changes of the viscosity of hy

ISSN:0038-9056    

DOI:10.1002/star.19900421106

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractInvestigations of the potato starch hydrolysis during bacterial α‐amylase liquefaction and saccharification with barley β‐amylase itself and with cooperation with pullulanase were carried out. In adequate conditions at different enzyme dosages hydrolyzates of the maltose content of 60 to about 85% in DS with significantly (6–10 times) lower maltotriose and minimal glucose content could be obtained. Investigations comprised both carbohydrate contents in hydrolyzates changing with hydrolyze course and dextrine molecular structure in hydrolyzates. It was found out that decreasing dextrine molecular weight and the number of branchings was accompanied by characteristic changes of the viscosity of hydrolyzate so

ISSN:0038-9056    

DOI:10.1002/star.19900421107

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractOrganic ligand containing coordination metal ion complexes and the organometallic compounds in which the metal atoms are covalently bound can form regular inclusion complexes with cyclodextrins. Organic ligands for complexation of the metal ions may be also appropriate substituent groups of a chemically modified cyclodextrin. With non‐derivatised cyclodextrins only so‐called Outer Sphere Hydroxo‐complexes are formed. Metallocenes, arenes, rotaxanes, rhodium‐ and platinum‐complexes are the typical metal ion or atom containing guest molecules. These complexes can be utilised as catalysts, enzyme models, siderophores, colour and fluorescence enhancing reagents, d

ISSN:0038-9056    

DOI:10.1002/star.19900421108

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe heptakis (2,3‐di‐O‐acetyl‐6‐bromo‐6‐deoxy)‐β‐cyclodextrin has been converted to the 6‐azido derivate with 82% yield, then deacetylated by theZemplén's method (yield 75%) and methylated by methyl‐iodide (yield 66%), to heptakis (2,3‐di‐O‐methyl‐6‐azido‐6‐deoxy)‐β‐cyclodextrin, which is an appropriate intermediary toward methylated amino‐CD‐derivatives. The structure of all compounds

ISSN:0038-9056    

DOI:10.1002/star.19900421109

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19900421110

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19900421111

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY