摘要:

AbstractLucerne (alfalfa) was harvested at different stages of maturity and the plants classified according to a phenological scale. The main class was separated into anatomical parts and analysed for content of extractives and crude protein and in‐vitro degradability. Whole crop samples were also analysed for polysaccharide residues, Klason lignin and in‐vitro degradability of crude protein and polysaccharide residues. The composition of the plant changed during maturation with an increase of the stem fraction from 18.5% to 50.7% of dry matter and a corresponding decrease in the leaf fraction from 72.9% to 18.4% of dry matter. The leaf fraction changed least in content of extractives and crude protein and in‐vitro degradability while in the stems all these paramaters decreased radically. Chemical analysis of residues after incubation with rumen liquorin vitroof whole crop samples revealed that the degradability of crude protein declined from about 90% to about 80% and of non‐starch polysaccharides from about 90% to about 60% during maturation. Xylose was the least degradable polysaccharide residue at all harvests. Xylose residues also showed the greatest decrease in degradability during growth. A comparison showed that stage of development and harvest date were of practically equal value as predictor of crude protein content in

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370102

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe following are summaries of the papers presented at a joint meeting of the Agriculture Group of the Society of Chemical Industry and the Fertiliser Society held on 15 October 1985 at the Society of Chemical Industry 14–15 Belgrave Square, London SW1X 8PS. The papers published here are entirely the responsibility of the authors and do not reflect the views of the Editorial Board of the Journal of the Science of Food and Agricultur

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370103

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAlthough a 2S globulin class has been observed in salt extracts from seeds of several lupin species, there have been conflicting reports regarding the importance of this class inLupinus angustifolius. Conglutin δ, a major sulphur‐rich protein extracted from mature seeds ofL. angustifoliuscv. Uniwhite, was separated by gel‐filtration into two oligomeric forms. The sedimentation coefficients of conglutin δ1(20%) and conglutin δ2(80%), were 3.2S and 2.0S respectively. The amino acid compositions of both oligomeric forms of conglutin δ were identical and similar to the compositions published for the 2S globulins in other lupin species. Because of the low level of tyrosine and the absence of tryptophan, conglutins δ1and δ2showed little absorbance at 280nm (E1%/1 cm−23). They were characterised by unusually high levels of glutamic acid and 1/2 cysteine (38.5 and 8.5 residues percent respectively) while methionine was absent. Gradient SDS‐PAGE showed that conglutins δ1and δ2were homogeneous single‐subunit species. On reduction, with or without S‐carboxymethylation, both the conglutin δ1and δ2subunits yielded similar pairs of large and small polypeptide chains. Since conglutin δ rarely resolves from conglutinaduring electrophoresis on cellulose acetate membranes in phosphate buffer at neutral pH, this method is not as useful for screening lupin cultivars as has b

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370104

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractFree sterol and phospholipid in the cortical tissue of apple were determined during storage of the fruits in air at 12 and 3.5°C and in 2 kPa O2(98 kPa N2) at 3.5°C. In air at 12°C, the sitosterol content declined slightly (about 4%) during fruit ripening whilst phospholipid increased about 8%. At 3.5°C in air and 2 kPa O2, sitosterol content increased by 16% and phospholipid by 25–31%. The increase in phospholipid in 2 kPa O2occurred more slowly than in air. Transfer of apples to air after 33 or 64 days in 2 kPa O2led to rapid accumulation of phospholipid in the fruit (20% and 10%, respectively) compared with apples maintained in 2 kPa O2. An increase in concentration of phosphatidylcholine (PC) accounted for most of the change observed in total phospho

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370105

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractLow levels of tannins (proanthocyanidins) have been detected in dried cassava (Manihot esculentaCrantz) samples using standard methods of analysis based on extraction procedures. A direct vanillin assay method was compared with other direct methods of analysis based on acid hydrolysis and protein precipitation. The specificity of the methods is discussed in relation to the levels of tannins detected and their potential biological activity in freeze dried fresh and dried/processed cassava samples. The results are discussed with respect to the amount of indigestible material present in the samples. The results of these experiments indicate that tannins present in dried/processed cassava products may be a factor limiting their nutritional value.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370106

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractChanges in the chemical composition of three popular Sudanese varieties of date (Jawa, Bentamoda and Mishrig Wad Laggai) during ripening are described and are related to changes in texture and in the activities of various degradative enzymes in the fruit. Total invertase levels were high throughout maturation of the three varieties. Although the proportion of soluble enzyme increased during ripening solubilisation did not appear to influence the relative amounts of sucrose and reducing sugars in the ripening fruit. Both cellulase and polygalacturonase were absent or at low levels in the green fruit but displayed large increases in activity during ripening. This enhancement was reflected in a reduction in fruit firmness although little change in cellulose or pectin levels was apparent analytically until the final stage of ripening. Despite a considerable rise in pectinesterase activity during ripening no significant trend could be discerned in the degree of esterification of pectin suggesting that the enzyme is of minor importance in softening of these fruit.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370107

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe 2‐thiobarbituric acid (TBA) test is widely used for measuring rancidity in foods. It is based on the colorimetric determination of a pink chromogen which is formed by reaction between TBA and TBA reactive substances (TBARS). Besides malonaldehyde (MA) many other substances have been reported to react with TBA. The formation of formaldehyde (FA) from the trimethylamine oxide (TMAO) decomposition in sea fish has been extensively studied. Considering that FA reacts with the TBA forming a white precipitate or cloudiness the interference of FA with TBA test is studied concluding that FA contents over 25 μg ml−1extract interfere with the colorimetric determination during the storage of frozen blocks of Patagonian hake (Merluccius hubbsi) filleted and mi

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370108

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractFifty‐seven samples of 10 vegetables and cereal products from the Orkney Islands were analysed for iron, copper and zinc. Twenty‐seven samples of all foods except beremeal were also assayed for thiamin, pyridoxine, vitamin C and total folate. Copper was found to be low in comparison to published values and the levels of iron and zinc were marginally lower for some vegetables. Thiamin levels in most vegetables and in the local speciality bread, ‘bannocks’, were also lower than published figures. Possible explanations for these findings are di

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370109

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe absorption and utilisation of iron in rats fed stewed beans, lentils, fenugreek and wheat bread were measured and compared with that of rats fed on casein. The results showed that59Fe absorption and utilisation were better on the casein diet. Fenugreek promoted absorption and utilisation of iron relative to other food commodities. Stewed beans inhibited both absorption and utilisation of iron. Lentils, in spite of retarding iron absorption, assisted the utilisation. Amino acids and phytate phosphorus content of these ingredients are thought to play a part.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370110

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractMyosin was isolated from bovinem. semimembranosusand gels were formed by heat treatment at different pH values and ionic strengths. The gels were subjected to rigidity measurements and their microstructure was studied by scanning electron microscopy. This article provides evidence that myosin can form two completely different gel structures in the pH range 5.5–6.0, depending on ionic strength. Fine stranded gel structures were formed at low ionic strength (0.25M KCl), whereas coarsely aggregated gel structures were formed at high ionic strength (0.6M KCl). The fine stranded structure had a higher rigidity than the coarsely aggregated structure. It was found that all fine strand myosin gels were formed from turbid solutions and the aggregate gels from clear solutions. When the pH was lowered to 4 in 0.6M KCl a strand‐type gel structure formed spontaneously on dialysis, even without heat treatment. This structure did not change in character on heating. It was concluded that the conditions required for the formation of strand‐type myosin gels were already present before the heat treatment and that the strands were made up of myosin filaments at certain pH and ionic strength combinations, which produced a turbid solution. The strand‐type structures were considered specific with regard to myosin interactions which was not the case for the aggregated structures. Variation of the heating temperature in the range 55 to 65°C had no major effect on the type of structur

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370111

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY