摘要:

AbstractFive laboratories collaborated in a two‐part study to improve and measure the accuracy and precision of amino acid analysis. The results of the unpublished first part allowed each laboratory the opportunity to optimise their own procedure. In the second part of the study reported here, three purified and six conventional proteins were analysed, each after three different preparation procedures (normal and extended acid hydrolysis, and following preliminary oxidation). Preparative effects reported in the literature were confirmed though not uniformly, and there were other, often unique, preparative effects. Well documented preparative effects are essential in matching analytical work to differing requirements. Results from one laboratory were excluded from further statistical analysis because of high replicate variation. The repeatability (within laboratory) coefficient of variation was 4.1% and for reproducibility (between laboratory) it was 13.1%. Discrepancies between best amino acid estimates for purified proteins and estimates calculated from published sequences (P<0.01) provided evidence of bias in five amino acids from one laboratory and in one from another. WhenP<0.01 was used as the discard threshold for conventional protein results, a total of 9.9% of best estimates were discarded: 8.1% were biased, 3.2% were outliers and 1.3% were both biased and outliers. When these values were discarded, 19 of 96 mean values changed by up to 4%, nine changed by 4‐8%, eight changed by larger amounts and the pooled coefficient of variation fell from 8.2% to 5.4%. At this threshold between zero and 31% of each laboratory's data on conventional proteins was discarded. A lower threshold (P<0.05) doubled the discard rate but had marginal effects on mean values and residual variation. AtP<0.01 less than 20% of biased estimates were also outliers and less than half the outliers were also biased. This means that only studies which examine both accuracy and precision will achieve maximum improvement in eit

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590402

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe walls of sclerenchyma, vascular bundle sheaths, and parenchyma at different maturities (internodes 2, 5, and 7 from the apex) of bermudagrass [Cynodon dactylon(L) Pers] were analyzed by UV absorption microspectrophotometry, and the results were related to wall digestibility. Sclerenchyma walls from internode 2 were degraded by rumen microorganisms, with only the middle lamella remaining. Undegraded sclerenchyma walls gave a UV absorption spectrum similar to that ofp‐coumaroyl and feruloyl arabinoxylo‐trisaccharides isolated from bermudagrass cell walls. Absorption maxima occurred at ˜ 245 and 320 nm, together with a shoulder at ˜ 280 nm. Sclerenchyma from the older internodes 5 and 7 showed only partial degradation of the secondary wall adjacent to the lumen. Spectra of undegraded walls from these internodes showed absorption maxima at ˜ 245 and 285 nm with a shoulder at ˜ 320 nm. Spectra of sclerenchyma walls that included the middle lamellae gave a higher absorption at ˜ 320 nm than did wall layers excluding the middle lamellae. Vascular bundle sheaths generally were similar in digestion patterns and spectra to those of sclerenchyma. Parenchyma cells in internode 2, which were totally degradable, gave low absorbance. Parenchyma cell walls from internodes 5 and 7 were degraded except for the middle lamellae in cells nearest to the sclerenchyma; parenchyma cells nearest to the stem centre were totally degraded. Spectra of parenchyma wall regions that included middle lamellae were similar to thep‐coumaroyl and feruloyl arabinoxylo‐trisaccharides, and absorbance values were low compared with sclerenchyma and vascular walls. Results suggested that esteror ether‐linked phenolic acids accounted for most of the UV absorption in young sclerenchyma and young and old parenchyma; lignin‐like aromatics increased in older, poorly digested sclerenchyma as ester/ether‐type compounds decreased. An estimation of the amount of ‘ferulic acid equivalents’ of the walls was made assuming all the absorbance at ˜ λmax320 nm was due to ferulic acid; older sclerenchyma walls had the highest values (160 mg g−1walls) and parenchyma walls t

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590403

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractIn‐situ disappearance of alfalfa hay, soybean, soybean meal and maize grain lipids and fatty acids were measured using two dairy cows. Bags were removed after 1, 2, 4 and 8 h incubation. Bacterial colonisation was estimated by labelling bacteria by a15N infusion into the rumen. Results were then subtracted from calculations. Bacterial dry matter, lipids and fatty acids were highest for alfalfa hay and lowest for soybean. Disappearance of lipids and fatty acids was significantly higher for maize than for the other feeds. Stearic and octadecenoic acids appeared in hay and soybean as products of hydrogenation but no distinction could be made between fatty acids leaving the bags and fatty acids appearing or disappearing due to hydrogenation. Complete linolenic acid hydrogenation seems to be limited by the rate of hydrogenation of stearic acid into octadecenoic acids. Nylon bags seem to be a valuable tool to estimate hydrogenation or protection against hydrogenation in high linolenic content feed

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590404

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractTwo local varieties, a white type and a red type, ofSorghum vulgarecultivated in Ghana were malted, using a micro‐malting method, and their malt characteristics studied and compared to that of a commercial barley malt. The optimal germination time, at 30°C, to produce a good malt of high diastatic power and extract from local varieties of these varieties was 4‐5 days. The local varieties were also found to have high diastatic activities of between 55 and 68% of the commercial barley malt. Hot‐water extracts of the well malted sorghum varieties were also found to have higher and sustainable amounts of free amino nitrogen than the commercial malt. The hot‐water extracts of sorghum malts were lower than the commercial barley malt, yielding about 66‐77% of the barley malt, but contained a higher glucose to malt ratio. In terms of varietal superiority, the white sorghum yielded higher malt extracts than th

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590405

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractMature seeds from a range of species from theVicieaetribe were analysed for vicine and convicine content. Quantifiable amounts of vicine were found in all theViciaspecies analysed but neither glucopyranoside was detected inPisumorLathyrus.The concentrations of both vicine and convicine were similar for bothVicia fabaandV bithynicabut in all the otherViciaspecies glucopyranoside concentrations were significantly lower. Seeds from three faba bean lines and one each fromV narbonensisandV bithynicawere dissected into their constituent seed parts and these parts analysed. Only trace quantities were found in the seed coat but concentrations of vicine ranging from 39 g kg−1to 81 g kg−1were detected in the radicle samples. The implications of these results in relation to the role of these compounds in the plant are discus

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590406

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractOak (Quercus incana, Roxb) leaves were subjected to steaming or autoclaving (1.05 kg cm−2) for 10 and 20 min. For the fresh whole leaves, both steaming and autoclaving did not decrease substantially the levels of total phenols (TP), condensed tannins (CT), ellagitannins (ET) and protein precipitation capacity (PPC). At a 1:2 (w/v) ratio of dry ground leaves and water, steaming reduced the TP, CT, ET and PPC by about 10, 29, 30 and 25%, respectively, whereas these values were 27, 54, 64 and 53%, respectively, on autoclaving for 10 min. Increase of treatment time did not increase the reduction in tannin. The reduction of tannin levels decreased on increasing the water content from 1:2 to 1:3 (w/v of leaves to water). The in‐sacco dry matter digestibility increased marginally on steaming or autoclaving. Various fibre fractions and lignin increased following the heat treatments. Proanthocyanidins (PAS) per g neutral‐detergent fibre or acid‐detergent fibre (NDF, ADF) decreased on autoclaving. The PAS in NDF per g leaves was almost similar whereas PAS in ADF per g leaves decreased substantially following autoclaving, suggesting that heat treatment increased the solubility of PAS in an acid‐detergent solution. This can introduce errors in the values obtained for fibre and lignin using detergent system of analysis. The extractability of PAS in 50% aqueous methanol also decreased following autoclaving. The data obtained suggested that this decrease in extractability is probably due to binding of PAS to proteins on heat

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590407

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe proximate composition and fatty acid content of spinach were determined in two processing stages. Crude protein and ash content were 2.89% and 1.96%, respectively. The total lipid content was 0‐61%. The predominant fatty acids were palmitic (16:0), hexadecadienoic (16:2), hexadecenoic (16:1), stearic and hexadecatrienoic (18:0 and 16:3), oleic (18:1), linoleic (18:2) and linolenic (18:3). Little loss was observed as a result of processing. Soluble protein content showed losses of up to 87% during processin

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590408

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractLarge numbers of volatile and non‐volatile components have been analysed and quantified in the search for an understanding of alcoholic beverage flavour, but little attention has been paid to interactions between these compounds. The extractability by dichloromethane of ethyl esters from a series of Cognacs showed a variation which was loosely related to the level of wood‐derived components present. When added to a redistilled brandy, potassium chloride had little effect on ester extractability, but sucrose, tannic acid and an oak extract significantly reduced the amounts of ethyl esters extracted. When a brandy was fractionated by high‐performance liquid chromatography, the fractions containing esters were associated with less desirable flavour notes, suggesting that part of the maturation process involves a reduction in availability of compounds giving rise to such characteri

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590409

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractTomato plants were grown in a calcareous soil supplemented with two organic wastes (sewage sludge and epicarp‐mesocarp of the almond tree fruit). They were irrigated at three levels of salinity caused by the addition of sodium chloride. N, P, K, Na, Ca and Mg were determined in the soil and tomato fruits. The treatments had a significant incidence on mineral content in fruit and soi

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590410

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractChanges in the content and chemical composition of epicuticular wax of susceptible and non‐susceptible ‘Navelina’ orange and non‐susceptible ‘ Satsuma’ mandarin fruits to rindstaining, growing in the area of Valencia (Spain), were studied. The epicuticular wax content of the susceptible Navelina fruits increases with ripening from 30 μg cm−2in July to 110 μg cm−2in January. The epicuticular wax content of the non‐susceptible Navelina fruits was similar to that of the susceptible ones. The epicuticular wax content of the Satsuma mandarin fruits was lower than that of Navelina orange fruits; it changed from 20 μg cm−2in July to 40 μg cm−2in January. In this study, no correlation between epicuticular wax content and susceptibility to rindstaining of the orange fruits was found. In general, alkanes, aldehydes and fatty acids are the major wax constituents, whereas the primary alcohols and the triterpenoids are the minor ones. The maximum incidence of rindstaining occurs at the end of October and the beginning of November, immediately after the major rate of increase of the fruit surface. Such an increase also concurs with the major hardening and facility of

ISSN:0022-5142    

DOI:10.1002/jsfa.2740590411

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY