摘要:

AbstractThe relationship between the degradability, determined with a commercial cellulase preparation, of the cell walls of various plant parts of Italian ryegrass, maize and red clover can be expressed asY = A ‐ Be−k1t‐Cek2t, whereY= percentage of cell walls degraded,t= reaction time,k1andk2are rates of degradation, andA, B, andCare constants whereA = B + C. Degradability of the cell walls of Italian ryegrass or maize could be predicted accurately from the absorbance of the filtrate at λmax282‐288 or 310‐324 nm. Treatment of cell walls of barley straw with 0.1 or 1M sodium hydroxide for 7 or 20 h degraded between 12 and 41% of the walls and led to the release ofp‐coumaric and ferulic acids, the amount increasing with concentration of alkali and treatment time; the less concentrated alkali released more ferulic thanp‐coumaric acid. Treatment with the cellulase preparation of the residues from alkali treatment showed that they were almost twice as degradable as the u

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320902

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractSeed extracts of ten legume species were subjected to isoelectric focusing in acrylamide gels and inhibitors of subtilisin, three other bacterial proteases, trypsin and chymotrypsin were detected by a negative‐staining technique based on the chromogenic substrate, acetyl‐D, L‐phenylalanine‐2‐naphthylester. In addition to complex patterns of trypsin and chymotrypsin inhibitor zones, most legume seeds examined exhibited one major and one minor inhibitor of subtilisin, and the other bacterial proteases. However, in cowpea and black gram only the major, and in lentil and soya bean only two minor subtilisin inhibitor zones were detected. Isoelectric points of the subtilisin inhibitors range from 4.4 to 5.9. The inhibitor patterns obtained by isoelectric focusing of extracts mixed with bacterial protease confirmed that inhibitors of the bacterial proteases represent a new type of inhibitor different from the well characterised trypsin and chymotrypsin i

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320903

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractHere the results of analyses of milk of Friesian cows imported into the University Teaching and Research Farm from Western Germany are reported. Twenty‐five of the cows were milked from the first day after parturition for a lactation of 305 days (average yield 3000 ± 88kg). The colostrum contained higher percentages of total solids (TS), crude protein (CP), fats and ash but lower lactose than the mature milk. Concentration of major minerals in the colostrum were higher than the corresponding values in the mature milk. The composition of the colostrum approached normal values on the seventh day after parturition. Contents of TS, CP, lactose and fats in milk were highest in the first month of lactation and then decreased with advance in lactation. The trends were highly significant (P<0.01). On the other hand, the concentration of the minerals increased except for potassium which decreased with advance in lactation with the trends being highly significant (P<0.01). The values obtained for the gross composition of milk (except total ash) were higher than those reported for the Friesian cow's milk in temperate countri

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320904

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractTechniques for maximising the extraction of nitrogen from the West African locustbean seed (Parkia filicoideaWelw.) have been investigated. Maximum extraction (93 %) of nitrogen was obtained using a meal:solvent ratio of 2% with 0.05M NaOH. However, from the economic viewpoint a meal:solvent ratio of 1% using 0.01M NaOH would be cheaper. This ratio extracted 82% of the seed nitrogen. Other solvents such as sodium chloride solution and calcium hydroxide were not as efficient.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320905

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractImmature harvest of cocoa to prevent losses due to pests and pilferage is common in Sri Lanka. The effect of maturity on the levels of some components of the Amelonado variety of cocoa grown in Sri Lanka is reported here. The major problem posed by immature harvest is the loss of fats which has been shown in this study to be of the order of 50% when the crop is harvested 1.5 months early, although the fatty acid composition does not vary significantly during this period. The pulp of immature cocoa pods contains less free sugars and produces less ethanol on yeast fermentation than pulp of mature pods but the methanol content of the distillate is higher in immature pulp. The pectin content of the pod endocarp declines as maturation proceeds.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320906

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractRadionuclide‐labelled glycerol triolein has been used to follow the fate of triglyceride lipids during the mixing of wheat flour doughs. After removal of residual free lipid by petrol extraction, initial fractionation of freeze‐dried dough identified the acetic acid‐soluble protein as being the only component involved significantly in work‐induced lipid binding during dough development under nitrogen, and also in lipid release on admission of air. Very little labelled lipid was found in either the water‐soluble proteins or the starch residue. Sub‐fractionation of the acetic acid‐soluble protein by ammonium sulphate precipitation from acetic acid‐urea‐cetyltrimethyl‐ammonium bromide (AUC) solvent showed bound lipid to be distributed almost entirely between high‐molecular‐weight glutenin and protein which remained soluble in the AUC supernatant even in the presence of 20% ammonium sulphate. Precipitated gliadins contained very little labelled lipid. However, significant levels were found in classical ethanol‐extracted gliadin, and were traced predominantly to the same supernatant‐protein owing to its solubility in aqueous ethanol. Examination of this AUC‐supernatant fraction showed it to contain a hitherto unreported protein which had a molecular weight of about 9000, was strongly complexed with tri‐glyceride lipid on a 1:1 molar basis and showed a tendency to aggregate in solution. Its amino acid frequency was found to differ significantly from both glutenin and purothionin, the latter containing in particular very much more cysteine than the supernatant‐protein. Representing 10% or more of the total gluten, this small, highly interactive protein is responsible for a significant, if not the major, part of lipid binding activity in dough and may well have a fundamental role in the formation of an insoluble glutenin structure through both —SH and hydrophobic interaction. Accordingly, the name ‘Ligolin’ is proposed

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320907

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstractα‐Tocopherol substantially affects the distribution of peroxidic compounds formed during the autoxidation of methyl linolenate and methyl linoleate. In the autoxidation of both these unsaturated fatty acid esters the proportion of monohydroperoxides with conjugated double bonds in thetrans, transconfiguration is reduced until at high concentrations of α‐tocopherol (5%) onlycis, transisomers are formed. In the autoxidation of methyl linolenate the proportion of hydroperoxy‐epidioxides is reduced and only monohydroperoxides are formed when 5% α‐tocopherol is present. The results are discussed in terms of recent findings concerning the mechanism of the autoxidation of unsatura

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320908

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe fermentation of macerated tea leaf in aqueous suspension has been studied both manometrically and in a suitably controlled fermentation vessel. Oxygen consumption proceeded rapidly at a steady rate for an initial period, termed the primary fermentation, then decreased sharply as the availability of simple polyphenol substrates became rate limiting. Maximum reaction rates were observed at 20‐35 mg ml−1total solids, as a result of substrate inhibition. At higher concentrations of solids reaction rates were also affected by diffusion effects within the leaf particles. At 50 mg ml−1total solids and 25°C the system approximated to Michaelis‐Menton kinetics with Km02= 5 × 10−5M and Vmaxcorresponding to a primary fermentation time (PFT) of 10‐15 min. The PFT corresponded with the attainment of maximum total colour and maximum level of theaflavins (TF) (often>30% of total colour). Beyond the PFT total colour remained constant, TFs decreased and non‐dialysable pigments increased with time. At fixed levels of dissolved oxygen and solids concentration>60 mg ml−1the proportion of TFs was inversely related to solids concentration. At 50 mg ml−1total solids TFs increased toca60% of total colour as the dissolved oxygen level was increased to 0.175 mM. As temperature was increased from 15‐35°C the reaction rate increased, the proportion of TFs decreased slightly and thearubigins of intermediate molecular wei

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320909

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe natural peroxidase and catalase of tea leaf were shown to be active under the conditions employed for the fermentation of minced tea leaf in aqueous suspension. Fermentations carried out under nitrogen with ethyl hydrogen peroxide, which is not decomposed by catalase, yielded predominantly thearubigins, a high proportion of which were polymeric in nature. Fermentations using an excess of hydrogen peroxide gave similar results. Fermentations under conditions of controlled dissolved oxygen using both air and hydrogen peroxide resulted in a pigment distribution intermediate between those observed using air alone and using ethyl hydroperoxide under nitrogen. Adjustment of the amount of hydrogen peroxide used to around 120 μmol g−1leaf resulted in a pigment distribution closely similar to that of a good quality black tea. A mixture of theaflavins was stable in the presence of air and tea polyphenoloxidase but decomposed rapidly to yield polymeric materials under the action of hydrogen peroxide and peroxidase derived from tea or horseradish. Kinetic measurements suggest that tea flavanols are generally poorer substrates for peroxidase than for catechol oxidase. However, the level of peroxidase is high and, furthermore, in view of the respective pH optima of the two enzymes, its action would be favoured as the pH falls during fermentation. It is postulated that the nature and distribution of the pigments formed during the fermentation of tea is governed in part by the relative actions of catechol oxidase and peroxidase. These actions are, in turn, influenced by the availability of oxygen and the action of catala

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320910

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractGroups of rats (30 males and 30 females) were fed stock diet and diets containing 350 g kg−1of cocoa beans (non‐irradiated or irradiated) for 18 weeks and observed for food consumption, haematological variations, changes in growth pattern and gross pathology. Even though there was no significant difference among the groups in haematological or gross pathological examinations, consistently less food was consumed by rats fed on diets containing either non‐irradiated or irradiated cocoa beans. Furthermore, weight gain and terminal body weights of rats fed on cocoa‐containing diets were less than those fed on the stock diet. Such differences, may at least in part, be due to alkaloids in the cocoa‐containing diets and not as a result of irradiation of

ISSN:0022-5142    

DOI:10.1002/jsfa.2740320911

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY