ISSN:0022-5142    

DOI:10.1002/jsfa.2740230202

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe alkaline alcohol bran‐pigment extraction method has been developed into a simple and reliable quantitative colorimetric method. A requisite quantity (0.1‐1.0 g, depending on the degree of milling of the sample) of rice powder is soaked overnight with a 1:2 (v/v) mixture of 2% aqueous KOH‐n‐propanol (1 ml for each 0.1 g powder). Next day, the balance of 10 ml of the solvent is added, the mixture vigorously shaken and centrifuged. The yellow‐brown solution is read in a Spectronic 20 (filter colorimeters did not give linear readings) at 400 nm. On plotting the absorbance/g/10 ml data expressed as percentage of that of the corresponding brown rice against the degree of milling, the values in three raw and one parboiled rice varieties fell into a single smooth curve. The extent of milling of an unknown sample could, therefore, be determined by testing its absorbance and that of the corresponding brown rice.The extractant chosen, selected from different solvent combinations, gave a clear extract and a negligible difference in reading between normal and red rice kernels. The intensity of the colour was maximum at about pH 10.5 and above, and its λmaxwas at 360 nm (but 400 nm was used for convenience). The colour was rather unstable, but was more stable in presence of excess rice flour. Hence it was necessary to use a constant rice‐to‐solvent ratio during the extraction for all analyses.The concentration of the extractable pigment in successive layers of bran decreased linearly from the outermost to the innermost layer. The fat content, on the other hand, first increased and

ISSN:0022-5142    

DOI:10.1002/jsfa.2740230203

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractGrain dimensions, density, bulk density, porosity and angle of repose of paddy and rice were studied with respect to (a) varietal difference, (b) effect of moisture content, and (c) effect of degree of milling.(a)Grain breadth and thickness were mutually correlated; all dimensions of milled rice were closely related to those of the corresponding paddy. Density was nearly constant at 1.452 g/ml in all rice varieties; in paddy, the value was around 1.182 g/ml for round varieties and around 1.224 g/ml for others. Bulk density varied appreciably in both rice (0.777–0.847) and paddy (0.563–0.642 g/ml), and so did porosity (41–46% in rice, 46–54% in paddy). These were related to the grain shape (l/b ratio); the more round the grain, the greater was the bulk density and the lower the porosity and vice versa. Angle of repose was relatively constant in different varieties of rice (average 37.5°) and paddy (average 36.5°).(b)With increasing moisture content, in rice, density decreased linearly; but the bulk density decreased twice as fast and the porosity increased owing to a concurrent progressive increase in the frictional property which decreased the degree of grain packing. In paddy, with increasing moisture content, density and bulk density increased, showing the presence of void space between the husk and the kernel; the angle of repose also increased moderately, but the porosity remained nearly constant.(c)Density of rice increased slightly with milling; but bulk density, porosity and angle of repose were markedly affected by the degree of milling. In general, with progressive milling, bulk density decreased at first and then increased, while porosity and angle of repose changed in reverse fashion—the changes being more pronounced in parboiled rice than in raw rice. Thus brown rice packed well and flowed freely; rice of intermediate polish, particularly parboiled rice, had poor packing and flow properties; and fully milled rice again packed and flowed well. The primary change in these was in frictional property, which affected the porosity and hence the bulk density. The frictional property in turn was related primarily to the surface fat content of the rice. The surface fat increased sharply on initial milling, more in parboiled rice, and then gradually disappeared on f

ISSN:0022-5142    

DOI:10.1002/jsfa.2740230204

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractGlycerol of recent biological origin can be differentiated from that produced from archaic sources of carbon, e.g. mineral oil or coal products, by measuring the14C content by liquid scintillation counting.In the case of synthetic glycerol derived from archaic carbon the count rate, i.e. background, was independent of the amount of sample added, while with natural glycerol the count rate increases linearly with the amount of sample. It is possible to detect 15% of natural glycerol in admixture with synthetic glycerol with a confidence of 99%.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740230205

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractA description is given of the quantitative determination by gas chromatography of soluble substances contained in sweet corn (Zea mays saccharata). The results obtained from these determinations have shown that quotients of sucrose to fructose and sucrose to glucose concentrations may be a good measure of the degree of maturity attained. Moreover, gas chromatographic analysis appears to provide a specific method of quality control for stored sweet corn.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740230206

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractWheat flour contains hydrolytic enzymes capable of reducing dramatically the viscosity of the aqueous solution obtained by high‐speed centrifugation of dough. Indirect evidence suggests this reduction in viscosity is largely due to the hydrolysis of glycosidic linkages in the non‐starch polysaccharides. Soluble proteins and starch contribute less to the viscosity of this dough liquor than do the flour gums. The glycanases in flour relatively rapidly hydrolyse the galactomannan, guaran and carboxymethylcellulose. Flour also contains a wide range of enzymes capable of hydrolysing nitrophenyl α‐ and β‐glucosides, α‐ and β‐galactosides, α‐ and β‐mannosides, α‐arabinoside, β‐fucoside and β‐xyloside. Both the glycanases and the glycosidases show pH optima within the range 4‐6 which covers the ran

ISSN:0022-5142    

DOI:10.1002/jsfa.2740230207

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractReactions at 35°C of orange oil in contact with air and water were investigated by gas‐liquid chromatography (g.l.c.) and by oxygen absorption measurements. Degradation of the orange oil was reduced in the presence of citric acid, but addition of sulphur dioxide caused a drastic increase, the extent and the rate of which were proportional to the initial concentration of the preservative. Several degradation products were identifi

ISSN:0022-5142    

DOI:10.1002/jsfa.2740230208

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractIt has been suggested in the literature that aldehydes are produced from the amino acids in roasting cocoa beans by the Strecker degradation. [U‐14C]‐L‐Leucine [U‐14C]‐L‐3‐phenylalanine and [U‐14C]‐L‐threonine‐were used in an investigation to confirm this mechanism. The labelled amino acids were introduced into ripe cocoa beans which were then fermented, dried and roasted under conditions approaching those of normal practice. The carbonyl compounds were collected as 2,4‐dinitrophenylhydrazones and identified by thin‐layer chromatography (t.l.c.) and autoradiography.The major products from [14C]‐L‐leucine and [14C]‐L‐3‐phenylalanine were isovaleraldehyde and phenylacetaldehyde respectively, which are the aldehydes expected from a Strecker degradation. Some condensation products and other radioactive carbonyl compounds were also noted. The degradation of threonine appeared to occur early in the roasting process and to be more complex. Acetaldehyde was identified and it is suggested that this was

ISSN:0022-5142    

DOI:10.1002/jsfa.2740230209

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe price of plain and medium quality teas sold on the London auction on two separate occasions was closely correlated to their theaflavin content. An equation including theaflavin content and the colour of the tea liquor was derived, and explained 60% of the variation in market price at any one time. A very close agreement was found between theaflavin content and a broker's valuation. It is suggested that the results justify the use of theaflavin analysis as an objective assessment of tea quality in research.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740230210

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractNutritional responses in albino rats on diets containing different leaf proteins at 1.6% nitrogen (N) were studied. From the data on 4‐week growth and protein efficiency ratio (PER), leaf proteins from 19 different plant species were placed in 4 different categories: (1) 5 of no food value, causing loss or negligible gain in weight of rats; (2) 6 of poor quality, inducing a weight gain of less than 15 g with aPERbelow 1.0; (3) 3 of medium quality, inducing a weight gain of 20–35 g withPERof 1.3–1.75; and (4) 5 of good quality, inducing a weight gain of more than 40 g with aPERgreater than 1.75. The last 5, all of them cruciferous leaf proteins, were nutritionally 66% as efficient as skim milk powder (SMP). The apparent digestibility (D) and true digestibility (TD) values, from experiments with either young and growing or adult rats, were close to each other for the medium and good quality categories of leaf proteins. The values differed considerably for the poor quality leaf proteins and were lower than those for good quality leaf proteins. TheTDvalues for carrot, beetroot, lucerne and cauliflower leaf proteins in adult rats were around 40, 74, 87 and 89%, respectively, with that for SMP about 90%. The biological values (BV) were in a narrower range than theTD, falling between 70 and 77 in growing rats and between 55 and 59 in adults.A pre‐extraction wash of carrot vegetation decreased the ash content in extracted leaf protein, greatly enhanced its digestibility without changing itsBV, while a hot acid wash of the heat coagulated leaf protein caused some improvement inBVbut none in digestibility. Among different leaf proteins, the nutritional inferiority was also associated with reduced diet intake, suggesting adverse acceptability factors. Various analyses suggested that the likely factors, singly or in combination affecting the quality of leaf proteins adversely, were associated with the occurrence of low N, high ash, high soluble solids, high phenolic: N ratios, and/or low organic sulphur: N

ISSN:0022-5142    

DOI:10.1002/jsfa.2740230211

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY