摘要:

AbstractThis paper examines the benefits and problems that have arisen from the use of xenobiotics in modern agriculture. Factors which control the transport and metabolism of xenobiotic molecules in plants and soils are considered, with emphasis being placed on the identification of topics which, in the opinion of the authors, are appropriate for increased research activity. The various approaches that are currently used for the analysis of xenobiotic residues in biological materials are also reviewed briefly.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590103

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe pigmentation pattern of tea leaf shoots grown under a canopy and without shade were analysed in order to investigate the effects of some cultural practices on North East Indian made tea quality. The chlorophyll, carotenoid and anthocyanin contents of tea shoots grown in the shade of trees were significantly higher than those from unshaded plots. On the other hand, the lower accumulation of catechins and/or higher pigment contents in shaded plants makes tea less astringent and with better colour and appearance. Furthermore, all the pigment contents, except chlorophyll, were found to be higher in pruned tea leaf than unpruned tea, thus enhancing the quality of made tea.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590104

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractSodium selenite, sodium selenate, and sodium selenate in a pill formulation were applied to three soils known to produce Se‐deficient herbage (<100 μg Se kg−1dry matter (DM)). The ability of the salts, applied in spring 1985, to ameliorate Se deficiency was followed over 3 years by taking four harvests each year. Selenate treatment at 10 g Se ha−1and selenate prill treatment at 20 g Se ha−1produced herbage with Se levels (geometric means) of between 0.57‐0.86 and 1.79‐1992 mg kg−1DM respectively in the first spring harvest after treatment. Selenite was less potent and selenite at 100 g Se ha−1produced a response in herbage closely similar to that of selenate at 10 g Se ha−1.Even at 300 g Se ha−1the selenite treatment produced herbage with only 1.00‐1.36 mg Se kg−1DM at the first harvest. Application of selenate in the prill form at 60 g Se ha−1produced herbage potentially toxic to grazing animals with 4.81‐4.94 mg Se kg−1DM. The addition of fertiliser N to Se‐treated plots increased total Se uptake at the first harvest by a factor of 4 and had a small effect on Se concentration. The Se concentration levels in herbage from Se‐treated plots declined exponentially (t1/2= 21‐43 days). On one soil derived from Lower Old Red Sandstone and lava, selenite at 300 g Se ha−1gave herbage with Se contents significantly above background

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590105

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe shelf‐life of iced sardine (Sardina pilchardus) was studied. The main changes which take place in raw fish were investigated by means of organoleptic assessments, chemical analyses (total volatile nitrogen (TVB‐N), trimethylamine (TMA‐N), trimethylamine oxide (OTMA‐N) and hypoxanthine) and physical measurements (GR Torrymeter readings and pH). The influence of both seasonal changes and fat deterioration were also considered. The results obtained indicate that TVB‐N and TMA‐N parameters are not good freshness indicators for this species, but Torrymeter readings and hypoxanthine values can be used as indicators of freshness. However, they must always be confirmed by a sensory evaluation. From the different combinations tried, the most highly significant degree of correlation was obtained between sensory evaluation and Torrymet

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590106

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractSections of internodes of growing maize stems were used to study the behaviour of cell walls of different tissues during in‐vitro degradation with rumen fluid. Tissues with primary cell walls‐middle lamellae, at early stages of development, were degraded completely. In specific tissues, newly synthesised secondary walls were highly digestible whereas the primary walls‐middle lamellae of these tissues were indigestible. These primary walls‐middle lamellae stained positively with acid phloroglucinol but showed no fluorescence. At pollination, when secondary walls were of considerable thickness, these walls were still completely digestible even though they stained intensely with acid phloroglucinol and showed reduced fluorescence. However, at some distance from the cut end of sections, the secondary walls of the elongated tube‐like cells of sclerenchyma tissue showed considerable reduction in digestibility. Cross‐sectional area and dry weight measurements of different stem tissues revealed the importance of secondary wall digestion of sclerenchyma compared with the thin‐walled parenchyma. Chemical treatment with KmnO4or NaOH resulted in colourless secondary walls after staining whereas primary walls still reacted positively. It was concluded that very small amounts of phenolic compounds (lignin) located in the primary wall‐middle lamella that are not removed by KmnO4and NaOH treatment are responsible for the decrease in digestibility of tissues during plant development. Histochemical ‘lignin’ reactions and fluorescence just detect phenolic compounds and cannot be correlat

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590107

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractStarch was extracted from the roots of four different cassava cultivars (Munihot esculentaCrantz) grown in Colombia and harvested on four different occasions with a view to determining whether there was any relationship between the physicochemical properties of the starch and the texture of the cooked roots. The organoleptic quality of the cooked roots was evaluated by a trained taste panel and found to vary in terms of both their glassy texture and their hardness. Studies of the gelatinisation behaviour of the starches by DSC and amylography (with a Brabender amylograph), of the pasting properties by viscography and of the viscoelastic characteristics by a Bohlin rheometer demonstrated some differences between the physicochemical properties of the starches but insufficient to account for the pronounced textual differences.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590108

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractExtracts of the pulp of mature fruits of African pear (Ducryodes edulis) were assayed for the activities of the cell wall degrading enzymes cellulase, pectin esterase, polygalacturonase and proteinase. All enzymes were found to be endogenous to the pear pulp. Studies on the softening temperatures of the fruit revealed that softening of pear pulp slices was negligible at room temperature (28°C) and 100°C but most effective in the range 60‐85°C. Moreover, there was a close correlation between this effective softening temperature range and the optimum temperatures of the cell wall degrading enzymes. These results suggest that the heat‐dependent softening of the African pear pulp may be due to induction of endogenous cell wall degrading enzymes b

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590109

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA method was developed for the detection of irradiation of chicken and chicken meat products. The method consists of the extraction of fat from chicken skin or a chicken meat product, separation of hydrocarbons with an alumina column and gas chromatography (GC) and GC‐mass spectrometry analyses of the hydrocarbons 16:2, 16:3, 17:1 and 17:2 formed from oleic, linoleic and stearic acids during irradiation. These hydrocarbons were only detected in irradiated samples at doses of 5 and 10 kGy. The mean concentrations of the hydrocarbons were linearly related to the dose levels of irradiation in the case of chicken fat. The concentrations of two of the hydrocarbons (16:2 and 17:1) gave the best correlation with dose. When a dose of 10 kGy was used, the concentrations of major degradation products were 1.5‐5.0 mg/kg fat. The same relationship was not found in the case of chicken meat products because the amounts of hydrocarbons detected after irradiation with the same doses were similar. On the basis of this study it was clearly demonstrated that it is possible to judge analytically whether or not a chicken sample or a chicken meat product has been irradiated at doses of 5 or 10 kGy. It should also be possible to recognise samples irradiated with doses below 5

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590110

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractCarotenoids were extracted from fresh orange peel with various solvents. Acetone was the most efficient of the solvents tested. Two successive extractions with acetone after an initial washing with either acetone or methanol were adequate to remove 89% of the total carotenoids. The extracts were concentrated, the carotenoids transferred to hexane and a crude pigment concentrate was obtained by hexane evaporation. Water washings prior to acetone extraction eliminated the solvent‐solvent transfer to hexane. The extraction residue was used for pectin recovery. Carotenoid removal from the peel did not affect the yield and quality of the pecti

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590111

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractMoisture content and enthalpy, growth rates, and phenolics of germinating grains ofSorghum bicolorMoench (SK) andSorghum vulgareL (LR) were evaluated as functions of steeping time, air‐rest and formalin treatments, and germination time. Results obtained showed that 24‐h steeping gave rise to the highest growth rate, which was greater for LR than SK. The moisture and enthalpy which gave rise to optimum germination rate were 0.48 and 0.48 kg kg−1, 422.69 and 392.32 kJ kg−1for LR and SK, respectively. Air‐rested steeping effected the maximum growth rate as well as high phenolics retention in the germinated grains. Formalin re‐steeping imparted 71.32 and 68.88 % reduction in phenolics in LR and SK, respectively, while causing very low growth rate in the seedlings. However, no significant difference was found (P= 0.05) between FRS and low‐temperature steeping for the t

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590112

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY