摘要:

AbstractLosses of nitrogen (N) through ammonia (NH3) volatilisation and denitrification were determined following the application of cattle slurry to grassland in autumn or spring. Denitrification was examined on two contrasting soils. A system of small wind tunnels was used to measure NH3loss and an acetylene inhibition technique for denitrification. Between 31 and 84% of the ammonium N (NH 4+‐N) applied in slurry was lost through NH3volatilisation. Acidifying the slurry to pH c 5.5 prior to application reduced these losses to between 14 and 57%. On a freely drained loam soil, denitrification from unacidified slurry applied in the autumn at 80 m3ha−1was continuous throughout the winter, with the maximum rate of 0.91 kg N ha−1day−1occurring a few weeks after slurry application. The total denitrification losses were equivalent to about 29% of the NH 4+‐N applied for this treatment and 41% for the acidified slurry. The nitrification inhibitor dicyandiamide reduced the amount of N lost through denitrification by 70% when applied with the slurry at 25 kg ha−1, by 55% at 20 kg ha−1and by 30% at 15 kg ha−1. The nitrification inhibitor nitrapyrin did not appreciably reduce denitrification. Denitrification losses were consistently small from slurry applied to the freely drained loam soil in spring, or to a poorly drained, silty clay in autumn or spring. Neither nitrification inhibitor was of benefit

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500202

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe feasibility of ensiling barley contaminated with ochratoxin A (OA) as a practical method of inactivating OA was examined in in‐vitro and in‐vivo studies. In the in‐vitro study, OA concentrations in barley decreased by approximately 68% after being ensiled for 56 days. To verify the destruction of the OA, a chick feeding trial was conducted. Samples of a toxin‐and mould‐free barley, mould‐contaminated barley, a barley sample naturally contaminated with OA or a barley with added OA were each divided into two equal portions, one of which was ensiled for a period of 28 days. The mould‐contaminated barley was naturally contaminated with Penicillium cyclopium andAspergillus flavus. Diets containing either the ensiled or non‐ensiled barley samples were then fed to 7‐day‐old Leghorn chicks for two 7‐day periods. Changes in feed consumption (RFC) and body weight gain (RWG) relative to control birds, feed to gain ratio and mortality were monitored. The OA concentration in the two OA‐containing barley samples decreased by 58% after 28 days of ensiling, but there was no improvement (P>0.05) in chick performance or mortality compared with the non‐ensiled diets. The average RFC values for chicks fed the mould‐ and OA‐containing diets were less than 50% of the controls and RWG generally less than 30%. In absolute terms, chicks fed the ensiled barley diets also performed about 6% poorer (P<0.003) than those given the non‐ensiled barley. Ensiling did not appear to be a practical method of reducing teh toxic effect(s) of OA, despite the apparent decrease in OA concentration. Grain sampkles should be tested for the presence of a toxin prior to ensiling to avoid possibl

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500203

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe sugar content was determined of 19 cultivars of swede (Brassica napusssprapiferaL) grown in rows 50 and 75 cm apart. Sugar concentration ranged from 54.3 to 78.7 g kg−1fresh weight and was positively correlated with dry matter content which ranged from 90.4 to 138.7 g kg−1fresh weight. The average concentration of fructose, glucose and sucrose in the dry matter was 225.0, 328.4 and 34.5 g kg−1DM, respectively. The high‐dry‐matter cultivars tended to have less fructose and more sucrose than the low‐dry‐matter ones, but total sugar concentration in the dry matter was not associated with dry‐matter content. Row width had little effect on sugar content compared with the differences between cultivars. The implications for the feeding value of swede

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500204

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAn in‐vitro method using commercially available enzymes for the prediction of the in‐vivo digestible crude protein content was developed and tested on seven feedstuffs and 16 diets for pigs. Fat‐extracted feed samples were consecutively incubated with pepsin at pH 1 and pancreatin at pH 6.8. From the nitrogen content of the feed sample and of the residue after incubation the in‐vitro digestibility of the crude protein was calculated. Using the linear regression of in‐vitro on in‐vivo digestible crude protein of samples obtained in feeding trials, the in‐vivo digestible crude protein content (DXPp) in g kg−1dry matter could be predicted. For feedstuffs and diets the correlation was 0.99 and 0.95 and the residual standard deviation 17 and 6 g kg−1dry matter, respectively. In a similar procedure the nitrogen solubilised during incubation with enzymes was analysed. The regression value was similar to that of the original procedure. However, this procedure was abandoned because it w

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500205

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe walls of the major plant cell types, sclerenchyma and parenchyma, of the second (upper) and fifth (lower) internodes from the apex of bermudagrass (Cynodon dactylonL) stem have been examined by ultraviolet absorption microspectrophotometry and the results related to wall digestibility (measuredin vitrowith rumen liquor) and to histochemical reactions for ‘lignin’ and phenolics. Sclerenchyma walls from the lower internode gave high values of absorbance in the ultraviolet region of the spectrum equivalent to 109 mgtrans‐ferulic acid g−1dry walls; similar walls from the upper internode also gave high values but these were lower than values from the lower internode. Histochemical examination showed that the sclerenchyma walls, which were indigestible to rumen microorganisms, gave positive tests with acid phloroglucinol reagent for lignin. Parenchyma walls, which were either digested or partially digested, gave much lower absorbance values in the ultraviolet region and negative tests with acid phloroglucinol but positive tests with diazotised sulphanilic acid (upper and lower internodes) and chlorine‐sulphite (lower internode) reagents. Ultraviolet absorption microspectrophotometry is a useful technique for examining phenolics within individual cell walls that vary in biodegr

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500206

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractOligopeptides ofL‐alanine up to ala5, were incubatedin vitroin either strained rumen fluid or suspensions of mixed rumen bacteria. The disappearance of substrates and formation of products were measured for 40 min, by which time ala3, ala4and ala5were almost totally hydrolysed. Ala2was more slowly hydrolysed, and accumulated in incubations with the other peptides. The pattern of formation of ala2but not ala3from ala4, and ala3and ala2but not ala4from ala5, suggested that the peptides were being hydrolysed by a dipeptidyl peptidase mechanism. Three different sheep receiving different diets gave similar results. Neither substrates nor products appeared to be accumulated intracellularly, except for ala2, and then only if protozoa were present. Protozoa were more active than bacteria in ala2hydrolysis, whereas bacteria had greater activities with higher homologues. Similar preferences were observed with glycine peptides, although unlike alanine peptides gly3and gly5were more slowly degraded than the dimer. These experiments suggest that protozoa are of importance in the accumulation and hydrolysis of dipeptides, whereas bacteria are responsible for the breakdown of larger molecules by a dipeptidyl peptidase mechanism that does not appear to involve accumulation within the cel

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500207

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractTwo high‐protein genotypes of pigeonpea (Cajanus cajanL), HPL 8 and HPL 40, were analysed for their nutritional quality characteristics, and the results were compared with those of normal‐protein genotypes (C 11 and ICPL 211). The protein content of the high‐protein genotypes was higher on average by nearly 20% but their starch content, the principal constituent of the seed, was lower by about 8%. The higher fraction (about 7%) of globulin, the major storage protein, was associated with a lower glutelin fraction in the high‐protein genotypes. The amino acid composition (g per 100 g protein) of the high‐protein genotypes was comparable with those of the normal‐protein genotypes. However, the sulphur‐containing amino acids methionine and cystine were noticeably higher (about 25%) in high‐protein genotypes when results were expressed in g per 100 g sample. No large differences in true protein digestibility, biological value and net protein utilisation were observed between HP and NP genotypes. True protein digestibility was significantly increased by cooking in both whole‐seed and dhal samples. The values for utilisable protein were considerably higher in high‐protein genotypes, suggesting their superiority from the nutrit

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500208

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractWhen common wheat (Triticum aestivumL) gliadins were separated by RP‐HPLC, a major doublet peak eluted at 47.20 and 47.94 min. This peak was consistently found to be absent in Durum wheat (Triticum durumDesf) gliadins separated under identical conditions. In Durum wheat gliadins a characteristic small peak eluted at 48.30 min followed at 50.47, 510.37, 52.80 min by larger peaks. The peak area ratio of the peaks eluting at 50.47 and 51.37 min was found to be 2.18 (±0.14). This ratio was found to decrease proportionally on contamination of Durum wheat flour with flour from some common wheat varieties. This ratio alone was not enough to detect and quantify adulteration by all varieties of common wheat. An alternative method was found whereby the peak emerging between 47 and 49 min in the Durum wheat gliadin elution profile was expressed as a ratio of the total protein applied. This ratio was shown to increase when Durum wheat flour was adulterated with flour from common wheat thus enabling quantitative estimation of the level of adulteration. A third method of detecting adulteration of Durum wheat flour is also proposed in which the peak emerging between 47 and 49 min is collected and the protein separated by PAGE. The presence of more than one band of γ/β‐gliadins is indicative of adulte

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500209

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractCoffee beverage bottled aseptically was tested in order to evaluate the more evident chemical and sensory changes occurring during storage. The decline in pH and the quality score correlated well at several storage temperatures. The sensory analysis permitted definition of a lower limit of pH at which the product's shelf‐life ended. The original panel scores were assessed by response surface methodology to obtain estimated scores for the different time/ temperature storage conditions.Knowledge of the kinetic rate constants of the decline in pH at different temperatures permitted correlation of the shelf‐life of the product with its storage temperat

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500210

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractProcessed cheese analogues were made with different fat and moisture in nonfat solids (MNFS) contents and used to study relationships between composition, microscopic structure, rheological properties and sensory texture. Fat contents ranged from 58 to 230 g kg−1and MNFS from 487.6 to 603.3 g kg−1. Regressions showed that those rheological parameters measured by uniaxial compression at large deformations and moderately high rates were best explained by linear combinations of MNFS, protein and fat. The moisture in the protein network acted as a plasticiser lowering the rheological parameters. Fat alone had little direct effect on the rheological characteristics under these conditions but at small deformations and low deformation rates it formed elastic inclusions that contributed to the properties. Examination of fracture surfaces in the SEM suggested that, during fracture, fat was squeezed out and acted as a lubricant.Maximum stress and work to maximum stress measured at moderately high deformation rates related best to the sensory results and described fracture of the cheeses.From the regressions, for 95% confidence limits, sensory analysis could theoretically measure changes within the range of composition tested of<0.1% in MNFS or fat. Of the rheological parameters only work to maximum stress was as sensitive. However, interaction between these compositional factors reduced the sensitivity in pract

ISSN:0022-5142    

DOI:10.1002/jsfa.2740500211

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY