摘要:

AbstractAnalysis by g.l.c. of ether–extractable steam volatile constituents of black tea from a high elevation tea estate in the Western Region (Dimbulla District) of Sri Lanka during seasonal flavour development, indicated the presence oftrans‐2‐hexenal,n‐butyraldehyde,cis‐3‐hexenol, 1‐octen‐3‐ol linalool, methyl salicylate and geraniol as the main flavour constituents. Of these, trans‐2‐hexenal and linalool showed appreciable seasonal changes in black tea. Leaf quality and manufacturing practices, particularly withering and fermentation, influenced the production of these compounds during black tea manufacture. It is suggested that the relative concentration of these compounds may be partly responsible for the typical flavour quality of Sri Lanka black teas and these may be used as indices o

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350112

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe ethylamine contents of tea shoots and made teas were derived witho‐phthalaldehyde and 2‐mercaptoethanol, and quantified by high performance liquid chromatography. The coefficient of variation of this method was 1.97% from eight analyses.The levels of ethylamine in tea shoots declined markedly during growth and senescence after plucking; they also declined in the extracts of fresh tea during the incubation at 37°C, but this decrease was completely inhibited by amine oxidase inhibitors.The content of ethylamine in high grade green teas was higher than in low grade teas, but was almost identical in high and low grade black tea. The mean contents of ethylamine in 22 green teas and 17 black teas were 6.76±3.07 μmol g−1and 6.40±1.82 μmol g−1,

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350113

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe amount and composition of volatile compounds in the volatile oils were compared between non‐withered tea and withered tea.Important differences in the aroma constituents were found in the amounts of E‐2‐hexenal, Z‐3‐hexanol ester, linalool and its oxides, and methylsalcylate. In withered teas, the amounts of Z‐3‐hexenol ester, linalool and its oxides, and methylsalcylate were much greater than in non‐withered tea, but the E‐2‐hexenal content was higher in non‐withered tea.From the results it was thought that the withering process has an important role in the formation of volatile compounds in tea shoots during b

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350114

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractTwenty‐four wines from four communes in Bordeaux were evaluated by descriptive analysis by trained assessors. The same 1976 wines were assigned quality ratings by Masters of Wine (MW). The major aroma difference between the wines was attributed to variation in the intensity of the ‘green bean/green olive’ character by canonical variates analysis (CVA) of the aroma descriptor ratings across wines. The CVA of the flavour by mouth ratings showed the wines to be discriminated primarily on the basis of astringency and bitterness. By multivariate analysis of variance across regions, and by examination of the configurations derived from the CVA across wines, it was shown that the wines did not vary significantly between communes. No significant difference between the wines in quality ratings of the MWs was

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350115

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe possible use of near infrared (n.i.r.) diffuse reflectance spectroscopy in the monitoring of automatic metering equipment used for fat, sucrose, dry flour and water in short dough biscuit production has been investigated. The experimental design involved randomisation of a standard pilot scale Lincoln biscuit recipe to produce calibration and prediction samples and comparison of n.i.r. results with the levels of ingredients determined from the recipe. The use of several strategies based on regression analysis for selection of the ‘best’ wavelengths for reflectance measurements for each analyte was investigated. A novel strategy based on computing the regressions on analyte concentration of all possible pairs of reflectance readings across the spectrum at given intervals is presented.The results of the experiments demonstrate that the precision of the n.i.r. method is excellent for all four constituents, but only the calibrations for fat are sufficiently accurate to be capable of detection of metering errors of ±5% relative to the total amount of fat in the re

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350116

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe possible use of near infrared (n.i.r.) reflectance spectroscopy for the prediction of the bread baking quality of wheat has been investigated. A number of UK wheat samples were studied using a monochromator system which enabled reflectance data between 1100 and 2500 nm to be measured. These data were correlated with protein content, α‐amylase as measured by Falling Number, and protein quality as measured by SDS sedimentation volume, with the result that only protein content was capable of satisfactory calibration against n.i.r. Furthermore, no improvements to the wavelengths currently available in filter instruments could be found for the measurement of protein in wheat.It is therefore concluded that for UK wheat at least, n.i.r. spectroscopy cannot provide a measurement of bread baking quality of wheat beyond that which may be predicted from protein conte

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350117

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractMethods for calculating the Metabolisable Energy (ME) of foods and diets are reviewed in the light of the current interest in diets high in dietary fibre.A new equation is proposed for the calculation of ME, taking into account the dietary fibre content of foods and its effects on the digestibility of proximate sources of energy. The equation has been tested against values for the ME of various diets determined by balance studies in human subjects, and gives results which agree within 3%. This agreement is much closer than that obtained with the other available methods for calculating ME, including those currently in use.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350118

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractA method for the reduction of methionine sulphoxide to methionine using titanium trichloride is described. This method, coupled with the gas chromatographic determination of methionine after reaction with CNBr, measures methionine sulphoxide by the increase in methionine values after reduction with titanium trichloride. Results obtained for total methionine by gas chromatography after reduction and CNBr reaction, showed close agreement with those obtained by ion‐exchange chromatography after performic acid oxidation. This method was applied to pure proteins which had been subjected to hydrogen peroxide oxidation, and to a wide range of food proteins. An evaluation of other, but less effective, reducing agents is briefly discusse

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350119

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350101

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY