摘要:

AbstractSeeds of the kidney bean (Phaseolus vulgaris) are toxic to developing larvae of the bruchid beetle (Callosobruchus maculatus), a major storage pest of many legumes. Insect feeding trials were carried out whereby the albumin and globulin protein fractions from seeds ofP. vulgariswere incorporated into artificial seeds. Both fractions were shown to be toxic and to contain haemagglutinating activity, implicating the seed lectins as being involved in seed resistance. Further feeding trials using different P. vulgaris lectin preparations confirmed the toxicity of these lectins and suggested that it was the E‐type lectin subunits (erythrocyte‐binding) which were the major antimetabolites. Indirect immunofluorescence investigations using monospecific antisera for globulin lectins showed that the lectins, when ingested by the larvae, bound to the midgut epithelial cells. It was suggested that the mechanism of lectin toxicity in this instance is analogous to that known to occur in the rat, namely that the ingested lectin causes disruption of the epithelial cells of the larval midgut leading to breakdown of the transport of nutrients into these cells, and the absorption of potentially harmful substances. This is the first time that evidence for the mechanism of lectin toxicity has been obtained in inse

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350402

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractPeptide‐bound methionine when reacted with CNBr releases methyl thiocyanate which is quantitatively measured by gas–liquid chromatography. Seeds of varieties of legume contain γ‐glutamyl‐S‐methylcysteine, which also reacts with CNBr to give methyl thiocyanate, which results in elevated apparent methionine values. An extraction procedure for its removal was developed and applied to many legume varieties. Methionine values agreed with those obtained by ion‐exchange chromatography after performic acid oxidation; an exception wasPhaseolus mungo(black gram). Samples ofPh. mungofrom several sources all contained substantial amounts of free methionine but, as no γ‐glutamyl‐S‐methylcysteine was‐present, the need for extraction was eliminated. For the determination of methionine in cereals, conditions were adapted to decrease gel formation in the presence of formic acid and CNBr, and to eliminate interference at the gas chromatography stage. This was achieved by a mild acid hydrolysis prior to CNBr reaction, conditions fo

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350403

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractIntact methionine residues in food proteins, including a limited number offish meals, have been determined using gas chromatography to measure methyl thiocyanate released after CNBr reaction. However, methionine values for certain fish products determined by that method have been found to be low and variable compared with those determined by ion‐exchange chromatography after performic acid oxidation. This was traced to the presence of a component of many fish meals that, when reacted with CNBr, gave a product which co‐eluted with the internal standard, ethyl thiocyanate. A method was developed to eliminate this interference and allow methionine determinations to be carried out using the same gas chromatographic proced

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350404

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractSilages were made from whole crop wheat and from separated ears and stems at two stages of growth. The stability of the silage during exposure to air was also studied. Fresh material, ears and stems harvested at the milk and dough stage, and silage and aerobic post‐silage exposure material of whole wheat plants were examined. Large differences were recorded in composition between the different parts in the fresh crop; material with 11% crude fibre and 81% digestibilityin vitrowas obtained from ears at the dough stage compared to 14.5% crude fibre and 75% digestibility at the milk stage. Material harvested at the dough stage was the most stable during silage and in the aerobic post‐silage exposure. The composition and amino acid content of silages is reported together with microfloral counts in crop, silages and after exposure to

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350405

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe production of ochratoxin A byAspergillus ochraceusand of ochratoxin A and citrinin byPenicillium viridicatumgrowing on previously sterilised barley for 200 days at 5, 10 and 20°C and a water activity of 0.85 is reported.A. ochraceusdid not grow at 5°C, multiplied slowly at 10°C but did not produce toxin. At 20°C the organism multiplied more quickly and produced ochratoxin after 19 days, which slowly disappeared over the next 150 days.P. viridicatumgrew slowly at 5°C but did not produce any toxin. It multiplied at 10°C and produced ochratoxin A which was only detectable during the period from 100 to 150 days. At 20°C both ochratoxin A and citrinin were produced. Ochratoxin A was detected after 10 days and was still present after 240 days, whereas citrinin was produced in large quantities between 118 and 129 days and then rapidly disap

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350406

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractFlavonol glycosides found in the leaves ofLeucaena leucocephalacomprised the 3‐arabinosides, 3‐rhamnosides and 3‐glucuronides of quercetin and myricetin, and quercetin‐3‐rhamnosylglucoside, at a total concentration of 3–4%. In cultivars of high productivity (Peru, El Salvador (K28) and Cunningham) all seven compounds occurred with a largely constant pattern of relative concentrations. However in the cosmopolitan form naturalised throughout the tropics the 3‐arabinosides were invariably absent. The same feature which was conspicuous on the high performance liquid chromatography trace, occurred with a low frequency (ca10%) in Peru and Cunningham. The pattern provides a quick method for identifying the provenance of commercial leucaena leaf meal, and also for detecting blending or adulteration with other leaf meals. The flavonol glycoside distribution of those species associated with ‘leucaena’ leaf meal (Acacia villosa, Calliandra calothyrsus, Manihot utilissimaand Sesbania grandiflora) is very different, and all have fewer compounds. All compounds occur in the apical tissue of young leucaena seedlings, enabling identification of cultivar from seed in 10 days. Comparison of leaf flavonol patterns forL. leucocephala, L. pulverulentatheir known F1hybrid, and an entity known locally in Java as ‘L. glabrata’ strongly suggest a hybrid

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350407

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe seed oil ofMalva parvifloraL. (Malvaceae) is known to contain glycerides of cyclopropene (malvalic and sterculic), cyclopropane (dihydromalvalic and dihydrosterculic), epoxy, and conjugated dienol acids. By preparative thin layer chromatography, the epoxy and conjugated dienol acids were isolated as their methyl esters. These were characterised ascis‐12, 13‐epoxy‐cis‐9‐octadecenoic (vernolic) acid, and 13‐hydroxy‐cis‐9,trans‐11‐octadecadien

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350408

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractFlavour precursors, theS‐alk(en)yl‐L‐cysteine sulphoxides, change considerably in both concentration and total amount during the growth of onions. For the brown onion cv. Pukekohe Long Keeper (PLK) and for the white onion cv. Dehyso, (±)‐S‐1‐propyl‐L‐cysteine sulphoxide (±PCSO) is the predominant flavour precursor, with (±)‐trans‐S‐1‐propenyl‐L‐cysteine sulphoxide (±PECSO) and (±)‐S‐1‐methyl‐L‐cysteine sulphoxide (±MCSO) in a minor role. For PLK the greatest concentration of all three precursors is just prior to bulbing (3.6±1.1 mg g−1fresh weight); for Dehyso the greatest concentration is at bulbing (4.6±0.6 mg g−1fresh weight); Both varieties show a mid‐season reduction in flavour precursor concentration (of about 45%), followed by a small but significant increase in ±PCSO concentration during the end of season leaf die‐down. The total amount of the three flavour precursors per bulb in both varieties shows a maximum in late January (360±107 mg for PLK, 602±144 mg for Dehyso). In the subsequent months there is a dramatic reduction in the total amount of ±PECSO and ±MCSO, and a slight reduction in ±PCSO. Both varieties show an increase in the amount of ±PCSO at leaf die‐down. The relative proportions of these flavour precursors change with bulb age and cultivar. These results suggest that white onions used for drying and processing could be harvested from bulbing onwards. Furthermore, when onion cultivars and onion plant selections are assessed for flavour

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350409

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe amino acids of prickly pear (Opuntia ficus indicaL.) proteins, free amino acids and nonvolatile organic acids were determined on fresh and lyophilised young pads. The calculated biological value of prickly pear protein was 72.6, relative to egg protein. Trace amounts of malonic, malic and citric acids in material collected at 1800 hours; traces 0.95 and 0.31 mg g−1, respectively. In similar material analysed at 0600 hours, the concentrations of those acids were 0.36, 9.85, and 1.78 mg g−1, respectively. Since there was a significant accumulation of the acids during the evening, crassulacean‐type metabolism is sugg

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350410

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractAn automated enzymic method for the analysis of cyanide in cassava and cassava products is described. A total of 300 analyses a day can be handled easily. A wide range of free (nonglycosidic) or bound (cyano‐substituted glycosides) cyanides (0.4–40 μg HCN ml−1) can be assayed in the extracted solutions. The upper limit of detection for the bound cyanide can easily be increased by another three‐fold by assaying it under partial hydrolysis conditions. The two enzymic methods, manual and automated on Technicon's AutoAnalyzer, agreed well for the free and the bound cyanide in the leaf and the peeled storage root

ISSN:0022-5142    

DOI:10.1002/jsfa.2740350411

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY