摘要:

AbstractDisappearance of cell wall components of untreated straw and straw treated with the ligninolytic white‐rot fungiPhanerochaete chrysosporium, Dichomitus squalensandCyathus stercoreuswere determined during the course of rumen digestion of samples in nylon bags. The first fungus degraded hemicelluloses and cellulose non‐selectively, adversely affecting the digestion rate of crude cell walls.Dichomitus squalensandC. stercoreuspreferentially degraded hemicelluloses and lignin, affording cell wall degradation rates 1.5 times higher than in native straw. Furthermore, the extent of cell wall digestion was also significantly enhanced. Both strains improved the extent of cellulose digestion, whereas the potentially degradable xylan fraction remained unchanged. Polysaccharide digestion rates were influenced in different ways depending on the strain tested: straw degraded byC. stercoreusshowed an increase in cellulose digestion rate by 50%, whereas residual arabinose units were slowly degraded. Xylan was degraded 1.8 times faster in straw decayed' byD. squalens, while cellulose digestion remained unchanged.Phanerochaete chrysosporiumdepressed both xylan and cellulose digestion rates. Fungal‐treated lignins were solubilised in the rumen faster than in untreated straw, whereas only treatment byC. stercoreusresulted in higher lignin losses. Esterified phenolic acids were extensively degraded by all three fungi. Residual ferulic andp‐coumaric acids accumulated during rumen digestion, although only the former decreased in the origina

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370202

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect of nitrogen application on the nitrogen content and yield of amino acids from potato tubers was studied in one experiment in 1983 and two in 1984. Increasing fertiliser N over the range 0–250 kg ha−1raised tuber nitrogen concentrations from 0.68–0.81 to 1.27–1.49% DM. Applying half the fertiliser on the seedbed and half at tuber initiation did not increase tuber nitrogen concentrations compared with a single broadcast application at planting. Increasing tuber nitrogen concentrations had little effect upon the proportion recovered in amides or the different amino acids. Yields of some nutritionally essential amino acids were, therefore, substantially increased up to a maximum of 256 kg ha−1in 1982 and 308 and 384 kg ha−1in 1984 at the highest fertiliser level. These yields were significantly higher (P<0.01) than those found with the nitrogen application rate optimal for tuber dry matter production (213, 195 and 331 kg N ha−1, respectively) in the same experiments. Methionine and cystine were the limiting essential amino acids. As the amount of each amino acid contained in a unit weight of fresh tuber increased with nitrogen supply, application of more nitrogen than is needed for maximal tuber dry matter production increased protein yields without decreasing the nutrit

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370203

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractGlasshouse experiments were carried out to examine the way in which potassium was redistributed within lettuce plants during development and alleviation of K deficiency, with a view to providing a more objective method of selecting the best leaf for sap analysis. The changes in distribution of K between leaves were measured by analysis of samples of petiole sap and were compared with the corresponding changes in overall K status of the plants determined by analysis of the total shoot dry matter. Young expanding leaves were most sensitive to alterations in external K supply: their sap concentrations changed more quickly than in any of the older leaves, but because of the inherently lower concentrations in these immature leaves, the overall size of these changes was ultimately less than in fully developed ones. Statistical analyses also showed that measurements of K in the sap from young expanding leaves were more precise than from mature ones. Relative changes in K concentration in the sap of these expanding leaves also occurred initially more quickly than in the total shoot dry matter, but measurements on the latter were considerably more precise. It was concluded that for sap K analysis the best results were obtained using an immature leaf.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370204

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe growth and inorganic ion composition of K‐sufficient lettuce shoots were measured after withholding K or K and Na from transplanting in sand culture experiments in the glasshouse. Initial reductions in shoot growth occurred shortly after transplanting in both K‐deficient treatments when the K concentrations were still well above that known to limit enzymic activity. These early growth effects coincided with a rapid decline in total ionic strength within the plants caused by the fall in K concentration which could not be compensated for by increases in the uptake of Na, Mg or Ca, even when adequate concentrations of all of these ions were available. Further rapid reductions in growth rate occurred when the concentration of K declined below about 600 mmol kg−1in both K‐deficient treatments. These results support the hypothesis of a dual mechanism for the effect of K concentration on growth during K deficiency. The primary effect was caused by a rapid decline in ionic concentration shortly after the K became unavailable which severely affected the mechanisms controlling turgor pressure within the plant. The secondary effect was caused by a reduction in enzymic activity and only became important when the K status of the plant was relativ

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370205

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of dry extrusion of mixtures of high‐glucosinolate rapeseed (cv. Jet Neuf) with barley, sunflower meal and rapeseed meal and a mixture of low‐glucosinolate rapeseed (Canola) and sunflower meal upon dry matter intake, utilisation of protein, liveweight gain and anti‐thyroid activity in rats, measured in terms of plasma thyroxine and tri‐iodothyronine, were studied in comparison with equivalent milled mixtures. Extrusion of the Jet Neuf mixtures increased dry matter intake, liveweight gain and biological value of the protein but only for the Jet Neuf/barley and Jet Neuf/sunflower mixtures did extrusion reduce the anti‐thyroid activity. Extrusion of the Canola mixture had no effect on the biological value or anti‐thyroid activity; in both respects it was superior to the Jet Ne

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370206

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe biological effects of pectic polysaccharidases ofPseudomonas solanacearumwere tested on the tissues of certain food plants. It was found that both the endo‐polygalacturonase (PG) EC.3.2.1.15 and endo‐pectate lyase (PL) EC.4.2.2.2 caused loss of cohesion of the cells, and leakage of K+ions. In addition the enzymes were highly toxic to the cells. Endo‐PL in particular causedca82.5% death of potato protoplasts within 1 h of incubation. Data on enzyme absorption showed that tomato tissues (a host plant) absorbed the enzymes whereas there was less absorption of the enzymes by tissues obtained from non‐hosts. These results suggest that the enzymes which are synthesised by the bacterium during its parasitic association with certain food plants affect vital physiological processes of th

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370207

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAn increase in the period of sorghum starch liquefaction (amylolytic period) resulted in a sharp increase in mash viscosity and a drastic drop in glucose recovery. The highest recovery (84%) was obtained with a liquefaction period of 5 min. The progress of the hydrolysis process was recorded by monitoring the change in sugar composition by means of h.p.l.c. The polyphenol content of the mash remained almost constant during the optimum hydrolysis process.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370208

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe trinitrobenzene sulphonic acid (TNBS) method has been shown by previous workers to give low results for chemically reactive lysine if carbohydrates are present in the sample. The major factor responsible has now been identified as loss of ϵ‐trinitrophenyl (ϵ‐TNP) lysine during the hydrolysis stage, while adsorption of ϵ‐TNP lysine by humins formed from carbohydrates during hydrolysis has been shown to be insignificant. The loss can be minimised by a reduction of the hydrolysis time without affecting the necessary degree of protein hydrolysis. A modified procedure is suggested which is shown to give very similar results to Carpenter's method (incorporating the Booth modification) for pure proteins and to the Silcock method in the presence of carbohydrates. ϵ‐TNP lysine hydrolysed for 90 min or D,L‐lysine taken through the trinitrophenylation procedure followed by hydrolysis for 120 min are the most suitable standards. The procedure can be completed in under 6 h and does not require the use of expensive equipment or hazard

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370209

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAntisera to thermostable muscle antigens (TMA) from 14 species of bovidae were raised in goats and/or sheep. To achieve species specificity the antisera were absorbed with serum from the other species. While the absorbed antisera to TMA of buffalo, impala, eland, waterbuck, wildebeest and oryx were rendered specific, the antiserum to cattle TMA cross‐reacted with buffalo fresh meat antigens (FMA) and cooked meat antigens (CMA) but not with buffalo thermostable muscle antigens. Fresh and cooked muscle antigens from these two species could be differentiated by the antiserum to buffalo TMA. A similar approach was used to differentiate the FMA, CMA, and TMA of kongoni, topi and wildebeest. Antiserum to cattle TMA proved useful in detecting the presence of beef meat in meat products that had undergone commercial sterilisatio

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370210

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractNon‐enzymic browning (NEB) of a traditional intermediate moisture meat (den‐deng) and dehydrated meat was measured by both aqueous trypsin digestion and lead acetate‐ethanol precipitation methods. Trypsin digestion did not interfere with NEB determination, and the addition of a glucose‐glycine NEB mixture to dendeng had no effect on NEB measured by the lead acetate‐ethanol precipitation method. Comparison of NEB measurements by the lead acetate‐ethanol precipitation method and an aqueous trypsin digestion method on dendeng containing added myoglobin and/or haem pigments showed that only the lead acetate‐ethanol precipitation method overcame errors which were due to the presence of these pigments. Spice pigments present in dendeng also interfered and led to high NEB values, while NEB increased markedly in the presence of coconut sugar. Results for NEB of dendeng and dehydrated meat stored for up to 12 weeks at 50°C were lower when measured by the lead acetate‐ethanol precipitation method compared to results by the aqueous trypsin digestion method, although both methods showed that NEB increased w

ISSN:0022-5142    

DOI:10.1002/jsfa.2740370211

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY