摘要:

AbstractThein vitrodigestibilities of starches isolated from 21 Australian wheat varieties were measured after gelatinisation, using porcine pancreatic α‐amylase. The starches were also converted into their hydroxypropyl derivatives and levels of substitution, and freeze‐thaw stability of the products assessed. Digestibilities varied between samples and were significantly correlated negatively with fat content of the starches. No significant correlations between digestibilities and any of amylose content, grain hardness or granule crystallinity were found. Efficiency of reagent usage during derivatisation and freeze‐thaw stability also varied between starches. Levels of substitution were not reflected in relative freeze‐thaw stabilities of the starch der

ISSN:0038-9056    

DOI:10.1002/star.19930451002

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractBiosensor for determination of starch was prepared by fixing a carrier with immobilized enzyme system on the tip of aClark‐type oxygen sensor. Enzymes amyloglucosidase, mutarotase, glucose oxidase and catalase were co‐immobilized either on the partially hydrolyzed nylon net or on the activated collagen membrane. In both cases the covalent bond was made in the presence of glutaraldehyde and cyclohexyl isocyanide. The prepared biosensors were compared from the viewpoint of a specific activity of the immobilized amyloglucosidase, of a linear response area of the biosensor to the substrate concentration, of the pH and temperature of the reaction mixture and of the biosensor stability. Biosensors prepared were used for the determination of starch in the samples of cultivaiting media for the monensin product

ISSN:0038-9056    

DOI:10.1002/star.19930451003

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effects of annealing on phase transitions associated with gelatinization at different moisture contents of an atypical non‐waxy rice starch exhibiting a clearer‐than‐usual glass transition were studied by differential scanning calorimetry. Consistent with observations on synthetic glassy polymers, annealing at temperatures below the glass transition for limited periods caused an elevation of Tgwhich is attributed to the slow relaxation of the amorphous regions of the starch granules to their equilibrium glassy states. The crystalline regions were significantly affected only after annealing at temperatures above the glass transition, the resulting increase in crystallite melting temperatures and narrowing of the gelatinization range being ascribed to crystal growth and/or perfection. Passage through the glass transition (which precedes crystallite melting) appears to give rise to an apparent endotherm which becomes even more prominent on sub‐Tgannealing of samples at low moisture contents. Annealing of an ordinary rice starch (with no clearly discernible glass transition) at a temperature below its onset gelatinization temperature (T0) produced effects which paralleled those observed after sub‐Tgannealing of the atypical rice starch. The conclusion drawn is that a glass transition is superposed on the crystalline melt at the leading edge of the single endothermic peak observed at high moisture contents. Where biphasic endotherms at intermediate moisture levels are concerned, however, the present results suggest that the first or G endotherm very likely arises from a glassy‐to‐rubbery state transformation while the second or M1endotherm is associated with crysta

ISSN:0038-9056    

DOI:10.1002/star.19930451004

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractA rapid HPLC method for measurement of lactic acid in corn wet milling steep water was developed. This technique is also suitable for simultaneous analysis of sulfur dioxide (sulfurous acid). Lactic acid and sulfur dioxide were analyzed using a Shodex Ionpak KC‐811 HPLC column with a Waters 410 refractive index detector within 11 min. In preparing steep water for laboratory batch steeps, lactic acid from 85% syrup must be diluted to 10% (w/w) and heated at 95°C for 24 h to obtain free lactic acid. Steep water solubles, developed as steep time increases, did not interfere with the analysis. Duplicated injections (64) of steep water gave an average coefficient of variation of less than 4% between duplicates for both lactic acid and sulfur dioxide. Coefficients of variation for pure sulfur dioxide and lactic acid solutions were less (2.2% and 0.2%, respectively). This HPLC method is rapid, precise, and suitable for automati

ISSN:0038-9056    

DOI:10.1002/star.19930451005

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThree Polish varieties of oat starch were subjected to defatting by a cold extraction with the chloroform‐methanol‐water (3:2:1) mixture followed by a hot extraction with 1‐propanol. A comparison of results allowed discussion of the effectiveness of the extraction procedures, their effect on the structure of original starch as well as the structure of oat starch‐lipid inclusion co

ISSN:0038-9056    

DOI:10.1002/star.19930451006

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe present investigation describes the isolation and partial characterization of a gummy polysaccharide derived from the bark powder ofCryptocarya wightianatree. The isolated polysaccharide is highly viscous, exhibits ‘pituity’ characteristics, and is composed of arabinose and xylose in 6:1 ratio, respectively. Preliminary fractionation by precipitation with alcohol gave four fractions of varying compositional and viscosity characteristics. The major fraction (58%) was composed of arabinose and xylose in 5:1 ratio, respectively, together with an unidentified peak (∼21%) coeluting at the ascending part of the arabinose peak. The gum has potential applications both in food and non‐food ind

ISSN:0038-9056    

DOI:10.1002/star.19930451007

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe pullulan‐hydrolyzing enzyme from the culture filtrates ofSclerotium rolfsiigrown on soluble starch as a carbon source has been purified by ultrafiltration (Amicon, PM‐10), ion‐exchange chromatography (DEAE‐Cellulose DE‐52) and gel filtration chromatography (Bio‐Gel P‐150). The enzyme moved as a single band in non‐denaturing polyacrylamide gel electrophoresis carried out at pH 2.9 and 7.5. The relative molecular mass of the enzyme was estimated to be 64.000 D by SDS‐PAGE and 66.070 D by gel filtration on Bio‐Gel P150. The enzyme hydrolyzed pullulan optimally at 50°C between pH 4.0–4.5, whereas, soluble starch was optimally hydrolyzed at a pH of between 4.0–4.5 and at 65°C. The Michaelis constant (Km) for pullulan was 5.13mg·ml−1(Vmax1.0U · mg−1) and for soluble starch, it was 0.6mg · ml−1(Vmax8.33 U · mg−1). The enzyme was observed to be a glycoprotein (12–13% carbohydrate by weight) and had a strong affinity for Concanavalin A. The enzyme hydrolyzed α‐D‐glucans in an exo‐manner, which resulted in the release of glucose as the sole product of hydrolysis. Acarbose, a maltotetraose analog, was found to be a potent inhibitor of both pullulan and starch hydrolysis (100% inhibition at 0.06 μM). The enzyme has been characterized as a glucoamylase (1,4‐α‐D‐glucan glucohydrolase

ISSN:0038-9056    

DOI:10.1002/star.19930451008

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19930451009

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19930451010

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0038-9056    

DOI:10.1002/star.19930451011

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY