摘要:

AbstractThe increasing garbage mountain is more and more recognized as an ecological threat. Space for landfills is limited and additional incineration capacities require high capital investments and pose additional envrironmental problems. In the FRG from total annual 14 million t of household waste, 700,000 t are non‐degradable plastic materials (polyolefines, polystyrene and polyvinylchloride), especially for packaging. Different strategies are being followed to reduce the 5% plastics in household waste: prevention, recycling, chemical valorization, thermic utilization (incineration) and use of degradable polymers. The latter are reviewed in detail: chemical modification of classical polymers into photo‐ and chemo‐degradable materials, physical mixing of 6–20% granular starch with polyethylene or polypropylene, coprocessing of more than 50% disintegrated starch with hydrophilic polymers like polyacrylate or polyvinylalcohol to biodegradable films for agricultural mulch or carrying bags, thermoplastic extruded starch with plasticiser containing more than 90% starch for blister packaging and disposables for fast food and finally biodegradable polyesters like poly‐hydroxybutyric acid (PHB) and polylactic acid, produced by fermentation

ISSN:0038-9056    

DOI:10.1002/star.19900420402

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractTheEwersmethod, based on the partial acid hydrolysis of starch, followed by measurement of the optical rotation of the resulting solution, is an official E. C. method and used for determination of starch purity (regulation 2169/86). Short reviews of the evolution of this method, the method based on calcium chloride dissolution followed by optical rotation measurement, and enzymatic methods, have been made. Several of the key parameters of the acid hydrolysis method have been examined, namely solution clarity, clarifier level, degree of hydrolysis, and evolution of optical rotation with time. Results confirm that starches from different plant origins do not behave similarly during acid hydrolysis. The present factors for the respective starches may need some minor refinement. Application of both polarimetric methods and the AFNOR enzymatic method to four different starch types, give mostly acceptable results. For ease of use, the calcium chloride method has advantages over its acid hydrolysis counterpart.

ISSN:0038-9056    

DOI:10.1002/star.19900420403

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractIonic biopolymer hydrogels were prepared by the cross‐linking of starches with sodium trimetaphosphate in alkaline medium at 40°C for 2 hours. The swelling capacity is relatively high — up to 310 g H20/g polymer. Salt solutions have a marked influence, and result in shrinkage but not in a total collapse. The effect of both the cross‐linker and substrate concentrations on the swelling and rheological properties was investigated. The influence of temperature and NaOH concentration on the rheological behaviour suggests that they are both significant in determining the gel properties because of the readiness of the diester phosphate bonds to undergo hydrolysis. The molecular weight between two entanglement points (Me) and the effectiveness of cross‐linking [ne(r)/ne(t)] were estimated from the observed Gp′ values, and those calculated from complete conversion of the cross‐linker. The effectiveness of cross‐linking lay between 0.2 and 2.74% for 10% wlw gels, and reached a maximum of 48.1% at the higher substrate concentration of 20% wlw.13C‐NMR signals from the anhydroglucose units became broader and decreased in intensity with rising cross‐linker concentration due to the restricted motion arising from the

ISSN:0038-9056    

DOI:10.1002/star.19900420404

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractThe non‐freezability of a portion of the water in maltodextrin solutions and gels was taken as a measure for polymer‐water interactions. The amount of non‐freezable water was determined by measuring the melting enthalpy of freezable water in dependence on polymer concentration by means of DSC. The amount of non‐freezable water or the water binding capacity of the maltodextrins depends on their mean molecular mass and distribution of molecular masses. The higher the P̄nthe higher is the amount of non‐freezable water at high polymer concentrations. The aggregation of polysaccharide molecules does not change the amount of non‐freezable water. The gelation in connection with phase separation effects only a weak change in the mobility of free freezable water. Overriding and accidental physical and chemical variables of influence are discussed with respect to the totality of polymer‐water interactions in

ISSN:0038-9056    

DOI:10.1002/star.19900420405

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractBased on the subsite structure of an α‐amylase fromBacillus subtilis, production of glucose from a substrate maltohexaose in the amylase‐catalyzed reaction was theoretically predicted as a function of time. The theoretical time course was found consistent with the experimental results, which were obtained by the determination of a product glucose with a commercial assay‐kit. Hence, glucose, product from a substrate maltohexaose, will be a useful probe for the amylase‐catalyzed

ISSN:0038-9056    

DOI:10.1002/star.19900420406

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractMaltotetraose, a linear tetramer of α‐D‐glucose, has many potential uses in the food and pharmaceutical industries because of its unique characteristics. A consortium of Nihon Shokuhin Kako Co., Ltd., Kirin Brewery Co., Ltd., Chiyoda Corp. and Yokogawa Electric Corp. has developed a continuous maltotetraose production process which uses an immobilized enzyme bioreactor system. Because maltotetraose syrup is a brand‐new saccharide having low sweetness and resistance to retrogradation, it has begun to be used as a property enhancer for various foods, powdering materials, saccharide for dry milk, liquid diets for the sick and a body reinforcement agent for refreshing drinks. In addition to the properties of nutrition and taste, the tertiary property of organism control has been discovered; that is, feeding with a maltotetraose‐rich corn syrup inhibits the growth of intestinal putrefactive bacteria such asC. perfringensand Enterobact

ISSN:0038-9056    

DOI:10.1002/star.19900420407

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

摘要:

AbstractIn order to have a full continuous starch hydrolysates production process, the use of continuous conversions catalysed by immobilised enzymes is necessary. With respect to this, immobilisation of β‐amylase on anion exchange resins and continuous conversion of maltodextrins to maltose syrups is investigated in packed bed column reactors at lab‐scale. It is observed that the type of carrier and the source of the β‐amylase are important parameters for the required capacity of the continuous process. Results show that, from the investigated enzymes, the commercial Spezyme BBA 1500L® β‐amylase preparation immobilised on Duolite A568® as preferred carrier gives the best results in terms of initial performance and stability under realistic conversion conditions (50°C, pH 4.5, 50% d.s. substrate). On basis of the present results, the process is promising in terms of applicability at plant‐scale aft

ISSN:0038-9056    

DOI:10.1002/star.19900420408

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19900420409

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19900420410

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19900420411

出版商:WILEY‐VCH Verlag GmbH    

年代:1990

数据来源: WILEY