摘要:

AbstractThe factors controlling the solubility characteristics of soya bean proteins consequent upon acid precipitation were investigated. Two processes of protein insolubilisation, fundamentally different in their effects, were identified. One, termed ‚pH sensitivity’︁, involved principally haemagglutinin and low molecular weight (2S) proteins, and was affected by exposure to low pH (4.5) in the presence of reducing agents; resolubilisation could be achieved by adjusting the pH to 7.6, but only at low ionic strength. The second process concerned a precipitation‐induced aggregation of the globulins which was produced in the absence of, and largely eliminated in the presence of, reducing agent. In this case, complete resolubilisation was afforded by readjustment of the pH to 7.6, either by back titration or dialysis against a phosphate buffer, but was not dependent upon the presence of reducing agent. The mechanisms underlying these insolubilisation processes were concluded to be mainly of an electrostatic nature, rather than ones involving disulphide exchange re

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320402

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe degree of mechanical damage imparted to starch granules during flour milling is of importance in relation to the baking properties of the flour. A calibration is presented which enables the degree of starch damage to be measured by near infrared reflectance. This technique is rapid and non‐destructive so facilitating quality control of a flour mill. The results obtained using 148 UK commercial flour samples were a correlation coefficient of 0.906 and a residual standard deviation of 3.5 Farrand units using 74 of the samples covering the range 6‐47 Farrand units. The calibration was obtained using log (1/R) data at 1442, 1580, 2060 and 2258 nm. The residual standard deviation increased to 4.2 Farrand units when the calibration was used to predict the values of 68 further samples of commercial flour. The wavelengths at which reflectance measurements were taken corresponded to overtones and combinations of vibration frequencies due to free and hydrogen‐bonded O—H bonds in

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320403

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe nitrogen content of barley grains and the viscosity and glucose content of an acid extract from the corresponding barley flour were used to predict, with sufficient accuracy for selection purposes, the hot‐water extract obtained after the samples were micro‐malted. Optimum procedures were established using grain samples from several varieties and environments. Prediction equations were obtained by multiple regression and tested using samples of spring and winter barleys from the Plant Breeding Institute breeding programmes. The accuracy of prediction was greater with spring than with winter barleys. Approximately 70 samples can be tested by one person in 1 day and only a small amount of seed (2 g) is required. The method is considered suitable for screening material from early generations of breeding programmes when numbers are high and quantities of seed are insufficient for micromalt

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320404

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe effects on yield and on grain and malt characters, of drought stress applied at different stages of grain development and ripening were studied in three varieties of spring barley grown in a glasshouse. Differences between variety means were found for most of the characters studied, but only for wort filtration time was there a significant interaction between variety and irrigation treatment. Grain yield was reduced by all the treatments involving drought stress and the reduction was greatest when stress was applied at heading and maintained for at least 14 days. A similar response was found for the number of ears per plant. Number of grains per main‐shoot ear was reduced by drought stress applied at heading but not when the stress was applied from 32 days after heading until harvest. Grain size was significantly reduced by all treatments. Raw‐grain characters known to be correlated with malt extract were found to be affected by the treatments: grain nitrogen content, barley extract viscosity and the rate of sedimentation of barley flour in ethanol were all increased by drought stress, the degree of response varying with the length and timing of the period of drought. Malt extracts were reduced by drought stress whether this was applied early or late in grain development. Malting loss and germinative energy were reduced, and wort filtration time increased by late stress. α‐Amylase activity in the germinating grain was unaffected by any of the trea

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320405

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe antimicrobial effect of the lactoperoxidase‐thiocyanate‐hydrogen peroxide system has been recognised in milk and other biological fluids. In this study the main object was to determine whether the inclusion of 10% rapeseed meal (RSM) in layers' diet could enhance the levels of the thiocyanate ion (SCN−) in eggs to a level required by the LP system to promote bactericidal activity in egg products. Twelve ‚Abor Acre’︁ pullets were divided into two lots, separately housed and maintained under similar conditions. One lot was fed on a basal diet and the other on an experimental diet containing 10% RSM. Both diets were of known composition, isoenergetic and isonitrogenous. Throughout the feeding trials (15 weeks) a record was kept of egg productivity, individual egg weight and layers weight. Subsequently, the weekly‐lots of eggs were analysed for thiocyanate ions (SCN−) by gas chromatography. The colour of each yolk was measured using the ‚Roche Colour Fan’︁ and organoleptic assessments were made for the detection of trimethylamine taint since the feeding of RSM has been reported to influence these factors. No significant difference was recorded in the average weight of eggs obtained from both groups. However, egg production was 15% higher with RSM fed hens which lost a little weight. No taint was detected in either set of eggs and no significant variation in yolk colour was noted. After 4 weeks the levels of SCN−reached 1.6 mg kg−1in the experimental eggs and then remained almost constant. The control set had an average of 0.5 mg kg−1SCN−. Hence an enhancement of the SCN−levels can be achieved in shell eggs by incorporating 10% RSM in the layers' diet. This enhancement is of the order claimed necessary f

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320406

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA method for the determination of dimethyl sulphoxide (DMSO) in aqueous extracts is described. DMSO is reduced using stannous chloride and hydrochloric acid to dimethyl sulphide which can be measured by gas‐liquid chromatography. Other sulphur compounds, including S‐methyl methionine, have no effect on the assay. Levels of DMSO in solution higher than 10 μg litre−1can be readily determined. In samples of brewery wort the levels of DMSO were within the range of 261‐411 μg DMSO litre−1and repeated determinations on two samples of beer gave mean values of 417 and 627 μg DMSO litre−1with coefficients of variation of 13.7 and 11.8

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320407

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractAn improved method for predicting the supply of available soil N has been developed, based on the concept of determining simultaneously the mineral N (NO3‐N+NH4‐N) present in the soil at the time of sampling, and the mineralisable N that would become available during the growing season through mineralisation of organic matter. The method entails the determination, by automated colorimetry, of NO3‐N and NH4‐N extracted from the soil by boiling with 1M KCl. The method was evaluated, in comparison with others, using 21 soils. The values for predicted soil N supply from the various methods were correlated with the amounts of N, summated over six harvests, in the herbage of perennial ryegrass grown on the soils in pots kept under uniform conditions. The method based on extraction by boiling with 1M KCl accounted for 80% of the variation between soils in herbage N yield. A second method, based on the determination of NO3‐N+NH4‐N extracted by 0.05M Ba(OH)2, was equally as effective but was considered less suitable for

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320408

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA rapid method for estimating the total glycoalkaloid (TGA) content of potato tubers is described which allows TGA content to be classified into three groups: (i) low TGA containing (<15 mg TGA 100 g−1fresh weight); (ii) high TGA containing (35 mg TGA 100 g−1fresh weight). The method is intended for use by plant breeders, particularly when high TGA content might be expected in hybrid clones where one or both parents is derived from a wild species. The TGA concentration in juice expressed from potato periderm and cortex tissue was assayed by thin layer chromatography. The method utilises a direct relationship which was established between the glycoalkaloid concentration in expressed juice and the TGA content of the whole tuber and enables up to 50 analyses to be completed in 1 day by one operator without the need for expensive eq

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320409

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA salt‐extractable protein has been isolated and purified from large (A‐type) wheat flour starch granules (Triticum aestivumcv. Maris Huntsman). This protein was the major species extractable with NaCl and because of its ease of extraction it was tentatively concluded that it was associated with the surface of the granules. It had a molecular weight of approximately 30 000 as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS‐PAGE) and an isoelectric point (pI) in excess of 10 as judged by analytical isoelectric focusing in polyacrylamide gel. The amino acid composition of the protein was quite different from those of wheat gluten proteins. A protein with similar properties was present on small (B‐type) Maris Huntsman starch granules and it could also be detected on A‐type granules from another variety of hexaploid breadwheat (T. aestivumcv. Flinor) as well as on A‐type granules from tetraploid durum wheat(T. durum). This protein was not present on starch granules prepared from germinated grains (Maris Huntsman). The protein had neither α‐amylase activity nor inhibitory activity against either wheat or hog pancreatic α‐amylases. Several other proteins could be extracted from A‐type starch granules but only after gelatinisation of the starch granule in the presence of SDS. The electrophoretic behaviour of these proteins was quite different from that of the NaCl‐extracted protein and the rigorous conditions required to separate the latter proteins from the starch granules suggested that they are internal compo

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320410

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA method is described for the estimation of free lysine which depends on its reaction with excess dimethylaminonaphthalene sulphonyl (dans) chloride to form dans‐5‐aminovaleraldehyde. This product is extracted into toluene, separated by thin layer chromatography and estimated by fluorimetry. The mean recovery of lysine added to casein hydrolysate using this method was 99% (s.e. 4.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320411

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY