摘要:

AbstractProcedures based on five methods of soil analysis for predicting potentially mineralisable N, and hence soil N supply, have been evaluated and compared with prediction based on total soil N. The effect of adjusting the analytical results for differences in soil temperature and water status between sites has also been examined. The evaluation was performed by calculating the extent to which the results accounted for variation in the amounts of N in the herbage of perennial ryegrass plots receiving no fertiliser N. The plots were situated at 18 sites throughout the UK: at some sites results were available for more than 1 year, giving a total of 29 site/years. The best prediction, accounting for 65 % of the variation in herbage N yield, was obtained when the amounts of ‚glucose’︁ extracted from the soils by 0.05M Ba(OH)2were combined with the amounts of NO3‐N extracted by 2M KC1, and the combined values adjusted for soil temperature and water status. A procedure based on the measurement of the NH4‐N released by autoclaving the soils with 0.01M CaCL2accounted for 51 % of the variation However, procedures based on (a) NH4‐N extracted by acid KMnO4, (b) non‐NO3‐N extracted by 0.01M NaHCO3, and on (c) measurement of the absorbance at 260 nm of NaHCO3extracts, were no more effective than was analysis for total soil N (less than 36% of the variation accounted for when values were adjusted for soil temperature an

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320302

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe emission of nitrous oxide to the atmosphere was measured for 2 years (1977‐79) from two clay soils (Denchworth and Lawford series) that had either been directdrilled or ploughed. On almost all sampling occasions the emission from directdrilled plots exceeded that from the ploughed plots by factors ranging up to 15‐fold. Rates of nitrous oxide loss reached peaks of 2.5‐3.0 mg N m‐2h‐1(equivalent to 0.6‐0.7 kg N ha‐1day‐1) from the direct‐drilled plots on the Denchworth soil. Emissions of nitrous oxide from the Lawford soil were only 10‐20% of those from the Denchworth soil. The total amount of nitrous oxide‐N lost during each year from the Denchworth soil was estimated to be 5.4‐8.6 kg N ha‐1from the direct‐drilled plots and 0.9‐5.6 kg

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320303

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractWheat straw was treated with 5 % sodium hydroxide, ozone, and 5 % sulphur dioxide at 70°C for 72 h, and the effect of treatments on the composition and the in vitro organic matter digestibility (IVOMD) by rumen microorganisms was studied. Ozone and SO2solubilised most or all of the straw hemicellulose, converting it into cell solubles, whereas sodium hydroxide exerted a limited effect in this direction. The level of cell solubles increased from 31.8 to 48.2 and 52.2% and that of the reducing sugars from 2.2 to 15.6 and 24.3%, by ozone and SO2treatments, respectively. The IVOMD of straw was significantly increased by 80% (from 44 to 80%) with SO2, whereas NaOH and ozone improved the IVOMD by only 50% (from 44 to 66%). The initial digestibility (ID at 6 h) suggested to represent substrate fermentability was significantly increased by SO2from 7.4 to 29.3 %. In the present study, SO2was found to be the most efficient treatment for wheat straw in terms of overall degradability and fermentability. The technological advantage of the proposed treatment lies in the low moisture content (40%) and the moderate temperature required (70°C), conditions which could be attained by solar system

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320304

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractFree sugars in wheat varieties, at different stages of grain development and differing in grain size and starch content per grain, were analysed to determine any relationship with grain size and starch content. Fresh and dry weight (mg per grain) of developing grain increased with maturity until 35 days after anthesis. Fresh weight declined after 35 days but dry weight remained almost constant. Water content increased until the 21 and/or 28 day stage and then decreased. Active starch synthesis started from 14 days onwards and continued until 35 days after anthesis. Free sugars (total sugars, reducing sugars, non‐reducing sugars and sucrose) per grain followed closely the changes in the rate of starch accumulation and, in general, were maximum at the 14 day stage followed by a decline up to 28 days, with no significant alteration afterwards. Presence of adequate amounts of soluble sugars in grain even when starch synthesis had stopped suggested that the supply of sugar precursors did not limit starch synthesis. None of the sugars was found to have a significant relationship with either grain size or starch content. A hypothesis explaining the termination of starch accumulation in developing cereal grains has been propose

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320305

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractProtein from flour and doughs mixed with a Do‐Corder at high temperatures in the presence and absence of oxidants (potassium bromate, potassium iodate and L‐ascorbic acid) was fractionated according to solubility into water‐, salt‐, alcohol‐, acetic acid‐soluble protein fractions and insoluble residue protein. All fractions were freeze‐dried and subjected to scanning electron microscopy to observe visually the changes in protein structure. Acetic acid‐soluble and insoluble residue protein are alike in structure, but the former was thermally denatured easily, while the latter was very stable to heat treatment. Salt‐ and alcohol‐soluble protein were not deformed, but the water‐soluble protein was deformed by heat treatment in the absence of oxidant. Oxidants generally promoted deformation of protein structure with the exception that bromate partly protected acetic acid‐soluble p

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320306

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA procedure for the fractionation of wheat bran carbohydrates with an emphasis on non‐starchy polysaccharides is described. After a complete extraction using a chloroform‐methanol (2:1) solvent, bran was destarched using amyloglucosidase and extracted using ammonium oxalate. Then delignification by sodium chlorite followed by hot water extractions was applied. Small quantities of water‐soluble hemicellulosic polymers containing glucose, xylose, arabinose with lesser amounts of galactose and mannose were removed by these three steps. The remaining holocellulose (of a low protein content) was extracted using 1M sodium hydroxide, and hemicelluloses A1 and B1 were separated from the extract. Hemicellulose A1 (5.4% of native bran) was determined to be a xylan containing smaller proportions of arabinose and glucose, whereas hemicellulose B1 (12.6% of native bran) was a complex mixture of several types of polysaccharides, the major one being a highly branched arabinoxylan. Hemicelluloses A4 and B4, obtained by 4M sodium hydroxide extraction of the residue after 1M sodium hydroxide treatment, had lesser amounts of arabinose compared with the respective fractions from the preceding step. For hexoses, higher proportions of mannose and glucose were found. α‐Cellulose residue retains 19.8% of p

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320307

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA study of the changes in the limonin monolactone content of Washington Navel oranges, grown on sour orange rootstock, from blossom until maturity was carried out. At the same time the changes in the limonin monolactone content in the leaves from the spring‐flush, adjoining the fruits used in the investigation, were studied. From the start of development of the fruits there was an important biosynthetic activity of limonin monolactone, as indicated by its accumulation up to a maximum of 47 mg per fruit—around 130 days after anthesis. Throughout the whole development of the fruit the total limonin monolactone content in the endocarp was found to be greater than in the peel. The limonin monolactone content in the leaves decreased gradually from the start of the experiment until 130 days after anthe

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320308

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractApple juice phenolic compounds: (+)‐catechin, (‐)‐epicatechin, chlorogenic acid, phloridzin, phloretin xyloglucoside, and the polymeric procyanidins from the dimeric to the heptameric, were separated by high‐pressure liquid chromatography on a CN column, run in the normal phase, using an acidified tetrahydrofuran‐hexane solvent gradient. Individual procyanidin fractions, of different degrees of polymerisation, were collected from the CN column and the isomers from each fraction were then separated on a C18 column, using a methanol‐aqueous KH2PO4solve

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320309

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA new method is described for removing low levels of oxygen from enclosed atmospheres. The scavenging medium is a film of polymer such as ethyl cellulose or cellulose acetate which contains a sensitising dye and a singlet oxygen acceptor. The acceptor reacts with singlet oxygen formed by the sensitising action of the dye when illuminated. It is shown that the scavenging rate depends on the oxygen permeability of the polymer and on the dye concentration. Removal of oxygen to the detection limit of 0.03 % oxygen is achieved using erythrosin and difurfurylidinepentaerythritol in ethyl cellulose and in cellulose acetate. Potential applications include removal of oxygen from nitrogen‐flushed packages of oxygen‐sensitive foods, essences and chemicals, as well as from vessels for anaerobic microbiol

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320310

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractQuantitative thin layer chromatography has been used to estimate the saponin content of whole soya beans (Glycine maxL. Merrill, cv. Williams) and a number of commercial soya bean products such as protein isolates and lecithin. Saponins were present in all these materials at concentrations ranging from 56 g kg‐1(on a dry weight basis) for whole soya beans to 3 g kg‐1for the protein isolate ‚Promine‐D’︁. Previous estimates indicate a saponin content of whole soya beans of only about 5 g kg‐1. It is suggested that this is an underestimate resulting from loss of material during the extraction procedures used in earlier method

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320311

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY