摘要:

AbstractThe action of sodium hydroxide on the rate and extent of loss of wall polysaccharides from wheat and barley straws incubated in the rumen of the sheep was studied using a nylon bag technique. Cellulose loss reached a maximum in straws treated with 10 g NaOH 100 g−1straw. Further increase in amounts of alkali applied resulted in additional solubilisation of straw constituents, particularly xylan, but did not further enhance cellulose degradation. Rates of degradation of isolated straw, cotton and wood celluloses correlated with three of four measures of cellulose crystallinity obtained by X‐ray diffraction and infrared analysis. Treatment of cellulose samples with 20 g NaOH 100 g−1cellulose did not affect rates of loss or produce detectable changes to cellulose morphology. Loss of acetic acid esters, which accompanied alkali treatment, did not relate to improvements to digestibility. The rate of loss of cellulose from delignified neutral detergent fibre (NDF) was that shown by the isolated straw cellulose, despite the presence of acetylated hemicellulose. Deacetylation of delignified NDF with NaOH or sodium methoxide did not enhance rates of xylose or cellulose loss. In lignified wall material (NDF) the molar ratio acetyl:xylose (approximately 1:3.5) and proportion of the major phenolic acids (p‐coumaric and ferulic acids) remained essentially constant throughout the course of degradation in the rumen. It is suggested that loss of phenolic acids, while not directly contributing to digestibility enhancement, may model the susceptibility of ester linkages formed between polysaccharide and polyphenolic material to alkali. The extent of solubilisation ofp‐coumaric acid produced by NaOH showed a linear relationship with cellulose digestibility. An upper limit of 40% acid detergent lignin and 55% of total phenolics were released by NaOH, the extent of release closely paralleling cellulose digestibility. Phenolic material resistant to alkali remained associated with wall polysaccharides and was not released from nylon bags until over 50% of cellulose (and hemicellulose) had been

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320802

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe effect of rumen ammonia concentration on microbial protein synthesis and fermentation was studied in three separate experiments. In each experiment three separate sheep were fed semi‐purified diets [designatedA(‘concentrate’),B(‘roughageconcentrate’) orC(‘roughage’)] and infused intra‐ruminally with five graded amounts of urea according to a randomised block design. Rumen ammonia concentrations remained low until the total nitrogen intake was about 10 g day−1after which rumen ammonia concentration rose rapidly. Rumen and duodenal ammonia concentrations were linearly related (r=0.90, 0.98 and 0.84 for dietsA, Band C, respectively;P<0.001). Microbial protein production did not increase when rumen ammonia concentrations exceeded 2.8 mM for dietA, 6.0 mM for dietBand 1.6 mM for dietC. DietsAandCproduced a propionate‐type fermentation while dietBwas characterised by an acetate‐type fermentation. Rumen ammonia concentration had no apparent effect on either concentration or the molar proportions of volatile fatty acids. There were no systematic trends in digestibility in relation to rumen

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320803

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe dietary availability of carotenes to the animal depends in part on the relative proportions of different isomers and these may alter during ensiling. The proportions of the more available β‐carotenes are higher in well preserved silages than in clostridial silages. Under anaerobic conditions only small losses of carotenes occur with acidtreated silages but the provitamins are degraded rapidly in some fodder plants in the presence of both acids and oxygen. The presence of nitrites in silages is considered to increase destruction of caroten

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320804

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractIn extracts of developing seeds of wheat (Triticum aestivumL., cultivars Scout 66, Cheyenne, Nugaines and INIA 66R) examined by polyacrylamide gel electrophoresis, gliadin proteins appeared at 12‐15 days post‐anthesis with mobilities covering nearly the whole range found with mature seeds. Some differences among extractants [2M dimethylformamide (DMF); 2M urea; 60% ethanol; the aluminium lactate‐lactic acid electrophoresis buffer, pH 3.2] in both intensity and occurrence of specific bands were observed. With immature seeds, 60% ethanol extracts produced a maximum number of bands and least background colour, but DMF and urea extracts showed bands from 12‐ to 15‐day seeds at least as well as 60% ethanol extracts despite more background colour. Aluminium lactate buffer extracts occasionally yielded bands not found with other extractants, but gave poor extraction from immature seeds and relatively heavy background staining with mature seeds, especially in thew‐gliadin (lowest mobility) region. A quantitative sodium dodecyl sulphate‐electrophoresis procedure1was used to follow the formation of proteins in various molecular weight ranges (cv. Scout 66 only). At 12‐18 days post‐anthesis, synthesis of protein of molecular weight 30 000‐37 000 accelerated, consistent with the onset and acceleration of formation of α‐, β‐, and somey‐gliadins. Protein in a band of 44 000 molecular weight formed in similar fashion. In other molecular weight ranges, gliadin bands could not be positively identified because of the complexity of the banding p

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320805

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA method is described for measuring the rate of flow and composition of bile entering the duodenum of the pig with minimal interference to the normal physiological processes of bile secretion. Eight pigs of 25‐30 kg initial liveweight were fitted with reentrant catheters in the common bile duct. Two different diets were used: these contained barley, fine wheat offal, white fish‐meal, minerals and vitamins (diet BWF), starch, sucrose, casein, maize oil, cellulose, minerals and vitamins (diet SSC). The flow of bile in 24 h was calculated from the rate of drop formation in a small Perspex drop chamber. Variation in flow between and within pigs was high. Mean values for total flow of bile, and of water, dry matter, ash, total lipid and total nitrogen in the bile were: 1733, 1656, 76.9, 18.6, 11.0, 1.9 g 24 h‐1, respectively, for diet BWF, and 1182, 1132, 49.7, 12.6, 8.1, 1.8 g 24 h‐1, respectively, for diet SSC. The hourly pattern of bile flow appeared different for the two diets; for both diets, however, bile was calculated to contribute a maximum of 15% of the total endogenous material added to digesta collected from the d

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320806

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe accumulation of lipid in embryos of lupin was found to be most rapid between 30 and 40 days after anthesis, coinciding with the stage of maximal dry weight increase of the developing seed. The percentage composition of oleic acid increased and that of linoleic acid decreased as the seed matured. Factors which cause premature cessation of embryo development are likely to affect adversely the oleate: linoleate ratio in the seed as well as the percentage oil content.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320807

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe polyphenolic content of the testa of two coloured flower varieties of beans grown in Wales was comparable with that of two coloured flower varieties of peas grown in eastern England. Testa tannins from both species had the same adverse effect on protein solubility, the inclusion of 15% testa producing a 7 unit reduction in protein solubility in 5% saline solution. Water extracts prepared from the testas also significantly inhibitedin vitrothe activities of trypsin, α‐amylase and fungal cellulase, and in all cases enzyme activity was restored on the addition of polyvinyl pyrrolidone, clearly indicating that the observed inhibition was due to the presence of tannins. Analysis of the whole grain revealed that, due to differences in the proportion of testa (approximately 13% in beans as compared with 10% in peas), peas had a significantly lower overall polyphenolic content. However, it is concluded that pea testa tannins may be of equal significance to bean tannins in animal diets since the formulation of isonitrogenous diets would require a greater proportion of peas due to their lower protein conte

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320808

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractAlkali heat treatment of soluble and insoluble proteins (lysozyme, phosvitin, α‐casein and keratin) in the presence of biogenic amines (phenylethylamine, histamine, putrescine and spermine) resulted in the formation of novel amino acids. Isolation of these compounds was achieved by using14C‐labelled amines and detecting radioactive zones on electrophoretograms of the acid‐hydrolysed proteins. Confirmation of identity was achieved for two novel amino acids which were synthesised. The mechanism was hypothesised to be the addition of amine to dehydroalanine and evidence was provided that the latter may originate, at least in some proteins, from serine residues. The yield of the novel amino acids was increased by prolonged heating, higher temperatures, higher pH and increased amine concentration. It was concluded that the reaction conditions employed in the present study were less severe than those encountered in many domestic and commercial food processes and that the novel amino acids could be formedin situin many foods, especially those with a high amine c

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320809

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA routine procedure was developed which enabled a complete quantitative analysis of the carbohydrate components of microbial products to be achieved within a few days. Using the procedure, the complete carbohydrate composition of two yeasts grown on hydrocarbons and a filamentous fungus grown on carbohydrate waste was determined. Glucose was the predominant sugar contained in the polysaccharide fractions from all samples. Mannose was present to a lesser extent and glucosamine was present in trace amounts. Galactose was found in trace amounts in one of the yeasts but was found in slightly higher amounts in the fungus grown on carbohydrate. Carbohydrates accounted for 22.4‐23.6% of the dry matter of hydrocarbon grown yeasts and 21.7% for the filamentous fungu

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320810

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe water‐holding capacity (WHC) of various sources of vegetable and cereal dietary fibre has been measured under different experimental conditions. WHC was measured by centrifugation and filtration. The results obtained suggest that prolonged soaking has no effect on WHC. Fibre agitation, the presence of buffer (pH 7.5), and the presence of bile salt (deoxycholate) also had no effect on WHC, except for never‐dried potato fibre (NDPF) (fresh fibre concentrate). WHC, however, does vary with the method of measurement and the WHC determined by centrifugation was greater than that determined by filtration. The differences in WHC between NDPF and dried potato fibre are not due to gross chemical differences in the fibre. The conditions used for the preparation of dietary fibre and the measurement of its WHC, therefore, must be carefully controlled before the role of fibre in the diet can be better underst

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320811

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY