摘要:

AbstractDenitrification in autumn removes nitrate from soil which may limit subsequent crop growth but also lessens the nitrate available for leaching. Autumn denitrification may therefore play a significant role in determining water quality because autumn and winter leaching of nitrate probably provides the greater part of the nitrate reaching groundwater from arable agriculture. The influence of soil carbon content on rates of denitrification during October and November 1987 was investigated in field plots of a continuous spring barley experiment which had large differences in soil organic matter content. Denitrification occurred between early autumn, when the warm soil became saturated with water, and late autumn when its temperature dropped to 6‐8°C. Gaseous N losses from plots with a low carbon content and given inorganic nitrogen were equivalent to 4.5 kg N ha−1, but those from farmyard‐manure‐treated plots with a high carbon content were 29 kg N ha−1, approximately six times greater. Measurements indicated that the high carbon content plots contained twice the denitrifying biomass of the low carbon content plots. The initial denitrification rate (Phase 1) of a laboratory measurement of potential denitrification gave a good estimate of denitrification in

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490202

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractRelationships between yield and the accumulation and metabolism of abscisic acid were examined on a kale (Brassica oleraceaL) crop grown during a dry summer in the UK under different degrees of water and/or N stress. Measurements were made on both irrigated and unirrigated plants given three rates of N fertiliser, incorporated in up to three different ways in the soil. Growth of the crop was severely restricted in all treatments where irrigation and N fertiliser were withheld.Substantial production and metabolism of abscisic acid occurred in all treatments during growth, with dihydrophaseic acid the major product. Irrigation treatments had no consistent significant effect on the concentrations of either abscisic acid or any of its metabolites, although individual N treatments did show small concentration increases for some of the compounds on the unirrigated plots. By comparison, the N treatments had large effects on the accumulation of abscisic acid and of dihydrophaseic acid (both as free acid and as its glucoside). The concentrations of each of these forms increased significantly with the amount of N applied, the response being modified by a small but significant effect of method of fertiliser incorporation due mainly to its influence on the pattern of N availability during the growing season. However, the concentrations of abscisic acid and some of the metabolites were only correlated with yield in the irrigated treatment.These results suggest that neither the accumulation of abscisic acid nor the ability of the plants to metabolise it were major factors in restricting the growth of kale under either water‐ or N‐stressed conditions in the

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490203

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper details experiments aimed at optimising the conditions for the determination of glucosinolates in rapeseed (Brassica napus L) using the colorimetric thymol procedure.Glucose could not be substituted for sinigrin when preparing a standard curve for glucosinolate determination unless a correction factor was employed. The value of this factor was found to depend on the concentration of sulphuric acid. Although the coloured complexes formed between thymol and either glucose or sinigrin were found to be unstable at 100°C, the sinigrin/ glucose colour ratio remained relatively constant for incubation times from 40 to 60 min. It was found necessary to increase the amount of thymol present to a final value of 0.23% to ensure complete reaction of glucosinolates. The revised method can be employed successfully for the analysis of glucosinolates in both seed and meal

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490204

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSurveys of major Brazilian foodstuffs demonstrated that peanuts and peanut products continue to be very susceptible to aflatoxin contamination. To prevent, or at least minimise, the problem the aflatoxins need to be monitored by a rapid and inexpensive screening method. The AOAC Romer method has been used and found highly reliable. However, the clean‐up step utilises anhydrous FeCl3and basic CuCO3which are expensive and not readily available in Brazil. Thus, the extraction (with a mixture of 270 ml methanol plus 30ml 40 g litre−1aqueous KCl) and clean‐up (150 ml 100 g litre−1aqueous CuSO4) steps of the method of Soares and Rodriguez‐Amaya (1985) were combined with the AOAC minicolumn to provide a rapid, inexpensive screening technique. Fifty‐two sample lots of peanuts and peanut products were screened by this and Romer's method, and the results were in complete agreement: 28 samples were negative, four100 μg kg−1. The results also agreed well when the extracts obtained by the two methods were su

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490205

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe degradability of starch from various feedstuffs was investigatedin vitroby incubation of 500‐mg amounts in 50 ml of a 3:1 rumen fluid/buffer solution at 39°C for 6 h. The rumen fluid was obtained from one of three cows fed on hay or hay and concentrate. The degree of degradation after 6 h incubation varied strongly for the 23 feedstuffs investigated. The degradation of starch from the same feedstuff in rumen fluid from a hay‐fed cow was significantly lower than in rumen fluid from a concentrate‐fed cow. It seemed that differences in degradability between feedstuffs were not determined by the ration of the donor cow, but merely by the properties of the starch. Processed feedstuffs showed a higher degradation of their starch than the unprocessed feedstuffs, independent of the ration of the donor cow. Particle size influenced degradation, but not of the starch of tapioca meal. A fairly constant ranking in degradability between the various feedstuffs was found. Fermentation of mixtures of feedstuffs showed about the same rate of degradation as found for the single products. Only when great differences in the degree of degradability existed was the degradation of the total starch enhanced. The time of collection of rumen fluid strongly influenced the in‐vitro degradation o

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490206

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractTwo thousand commercial broiler chickens of both sexes were used to study the effect of temperature (21°C constant (LT) vs 21 to 30 to 21°C cycling (HT)), and dietary energy (13.0 MJ ME kg−1(LE) vs 13.8 MJ ME kg−1(HE)) on the live performance, blood pH, Pco2, Po2and HCO3and on heart, liver, gizzard and abdominal fat weights as proportions of body weight. Weights and analytical samples were taken at 34 and 54 days. Daily gain was depressed by HT (P<0.05) but HE overcame this depression in female broilers. The HT treatment reduced (P<0.05) blood pH and Po2, but increased (P<0.01) Pco2and HCO3levels especially when LE diets were fed. Heart, liver and abdominal fat proportions were all reduced (P<0.05) by HT in male broilers. Female broilers on HT had reduced heart proportions whereas liver and abdominal fat proportions were increased (P<0.001) especially in those fed HE diets. Gizzard proportions were increased (P<0.05) by HT, and reduced (P<0.05) in birds fed HE diets. Up to 34 days, for both sexes, a combination of LT × LE was superior to all the other combinations. By 54 days, LT × HE and HT × HE were advantageous for males and females, resp

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490207

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractUsing 34 carbon and four nitrogen compounds, and 12 standard yeast identification tests, eight isolates ofSaccharomyces cerevisiaeHansen fromRaphia Beaur(Palmae) palmwine and other sources were evaluated comparatively for morphological and physiological characteristics. Differences among the isolates were found mainly in their formation of pseudomycelium and blastospores, and in the fermentative utilisation of galactose, maltose, melibiose, raffinose, trehalose and α‐methyl‐D‐galactoside. The wine isolates varied primarily in their assimilatory capabilities for lactic acid and maltose. Observed fermentative and assimilative differences among the wine isolates confirmed the presence of physiological races ofS cerevisiaeinRaphiapalmwine, and suggest that physiological races ofS cerevisiaein palmwine may influence the wine's organoleptic and aromatic qua

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490208

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA quantitative method was developed to determine by gas‐liquid chromatography the concentrations of indole and skatole in pig fat. Methanolic extracts of subcutaneous adipose tissue were de‐fatted by cooling, concentrated using solid‐phase extraction columns, and analysed in a gas chromatograph fitted with a polar capillary column and a flame ionisation detector. The method detects indole and skatole to below 0‐002 mg

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490209

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe non‐destructive determination of the moisture content of wheat samples as small as an individual grain would have a range of uses whether for repeated measurements, as in physiological studies of development, or to allow subsequent analysis for other factors such as pesticide residues. However, no such method has yet been described. A suitable method has now been developed using an ordinary nuclear magnetic resonance (NMR) spectrometer. With a calibration set of 100 grains, the relationship between NMR response and oven moisture content (range 3‐3 to 19‐6%) was described by a full quadratic model with which there was no remaining lack of fit (1‐465 ns), and the repeatability of the model was acceptable (standard estimate of error 0‐9995). The quality of fit of the NMR predicted moisture content to the oven moisture content for three test sets each of 100 grains was also satisfactory (standard deviation of difference 0‐973 to 1‐352). Using two batches of 25 fumigated grains, the method has been used to show that the different amounts of residues of 1, 1, 1‐trichloroethane were not related to moisture content, as had been previ

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490210

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAutolytic processes are important factors in the deterioration of fish material. The effect of proteinase inhibitors from potato tubers in inhibiting the proteolysis in stored, ground herring was studied. Using an extract from potato, which was found to contain inhibitors for trypsin, chymotrypsin, carboxypeptidase A and carboxypeptidase B, the autolysis as measured by TCA‐soluble protein was profoundly decreased, as were the contents of free amino acids. The potato extract preserved the contents of total arginine, tyrosine and lysine in the samples of stored herring, and the levels of histamine, putrescine, tyramine and cadaverine were reduced. The addition of proteinase inhibitors gave a somewhat lower content of total volatile nitrogen, and the total viable count of bacteria was reduced to some exten

ISSN:0022-5142    

DOI:10.1002/jsfa.2740490211

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY