摘要:

AbstractWheat starch contains large lenticular (A‐type) and small spherical (B‐type) granules, with some intermediate (underdeveloped A‐type), composed of two structurally different polysaccharides, amylose (20–30%) and amylopectin (70–80%), plus small amounts of lipids, nitrogen and phosphorus. Vitreous character is related to air spaces between granules, whereas hardness relates to protein‐starch bond strength and protein matrix continuity between granules. Grain hardness is controlled genetically by one or more major genes, modified by one or more minor genes. Environmental factors also exert effects. Most hardness measurements are grouped into categories based on grinding, crushing, abrasion or indentation. Recent methods, viz microscopy, NIR, single kernel cutting, tensile strength and an acoustical technique, seem to have promise.Three basic mechanisms of grain hardness have been postulated: (a) chemically induced adhesion between the protein matrix and starch granule, (b) continuity of the protein matrix, and (c) net charge on the protein. Some recent studies have revealed small amounts of protein as an integral component of the starch granule. The surface granule proteins showed relatively low molecular weight polypeptide bands (5–30 kDa), whereas the integral starch granule proteins had higher molecular weights (59–149 k Da). The 59 kDa protein is postulated to be the enzyme that synthesises amylose. The 15 kDa polypeptide is related to kernel softness, because it is strong in soft wheats, weak or faint in hard wheats, and absent in durum wheats. Reconstituted tablets made from hard wheat starch showed higher tensile strength than those made from soft wheat. Tablets reconstituted from soft wheat starch free from 15 kDa protein exhibited increased tensile strength, suggesting that the 15 kDa protein acts as a ‘non‐sticking’ agent between the starch granules and the protein matrix. Some lipids are associated with arnylose and the starch granule surface but their significance is not clear. Key words. Starch, kernel hardness measurement, hardness mechanism, st

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560102

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractGarlic (Allium sativum L) cell cultures, unorganised white as well as organised green callus, revealed a total of five amino acid precursors (methyl, propyl, allyl, cysteine sulphoxides) and two unidentified ninhydrin‐positive compounds. All the five compounds were hydrolysable by alliin lyase to yield pyruvic acid. Their relative concentration varied in the cultured systems and the explant. The total flavour substrate index in globular white callus and semi‐differentiated green callus was 4 and 13% respectively of the original explant. In contrast to the substrate levels, the specific activity of alliin lyase enzyme showed half the original activity of the garlic bulb explant. The relationship between intermediary metabolism and flavour formation was studied in these cultures with the help of14C‐glucose and14C‐methionine. The incorporation of14C label was lower in the protein, carbohydrate and lipid fractions with a concomitant higher incorporation in the volatile fraction of semi‐differentiated cultures, whereas this trend was reversed in the white globular callus.14C Conversion to the flavour fraction was much lower in the in‐vitro cultures when compared with the garlic bulb.The activity of some enzymes such as amino transferase, malate dehydrogenase, polyphenol oxidase, peroxidase, and alkaline phosphatase was higher in the cultured cells than in garlic bulb. There were differences also in the protein, free amino acid profiles and peroxidase isozymes of garlic cell cultures and the origi

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560103

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractConcentrations and distribution of glucosinolates in various organs of rape (Brassica napus L) were examined during major stages of development. Fluctuations in the total content as well as in the individual levels of glucosinolates were investigated in double low Drakkar and high glucosinolate Chine 32 cultivars. The distribution pattern of aliphatic and aromatic glucosinolates between the various organs, as well as the variation in the concentrations of individual glucosinolates during plant development were quite similar between the two cultivars. Peculiar stages of accumulation during the vegetative growth period and the seed maturation period were identified. These stages were followed by periods of intense degradation during flowering, germination and early growth stages of seedlings. Fluctuations in the amount and structure of the glucosinolates in each of these periods suggest a storage function for these compounds which are required at specific stages of development. The involvement of some of these compounds in hormonal control of flowering is also discussed.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560104

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA total of 387 samples comprising animal feed, poultry feed and cattle cakes from India were examined in order to isolate mycotoxin‐producing fungi as well as mycotoxins. Of 385 Aspergillus flavus group isolates 53% were capable of producing aflatoxins in liquid SMKY medium. Toxigenic strains of other mycotoxigenic fungi, viz A ochraceus, A versicolor, Penicillium citrinum and Fusarium moniliforme, were also recorded. In feed samples, beside the aflatoxins present in 139 samples zearalenone, ochratoxin A and citrinin were also recorded alone or as cocontaminants. A monsoon climate together with the socioeconomic conditions of this region are important determinants for the high incidence of mycotoxins in animal foo

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560105

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA new technique for the analysis of flavonoids in honey has been developed. This uses filtration of honey through Amberlite‐XAD‐2 and purification of the flavonoid fraction by Sephadex LH‐20. The flavonoid fraction is then analysed by HPLC. This technique allowed the identification of 16 flavonoids in honey, namely quercetin, kaempferol, 8‐methoxykaempferol, quercetin 3‐methyl ether, isorhamnetin, kaempferol 3‐methyl ether, quercetin 3,3‐dimethyl ether, quercetin 3,7‐dimethyl ether, galangin, luteolin, apigenin, genkwanin, chrysin, luteolin 7‐methyl ether, pinocembrin and pinobanksin. The flavonoids present in ten samples of honey from La Alcarria have been HPLC analysed by this technique. The fact that the flavonoid patterns are very similar, suggests that samples from other areas should be examined in order to assess if this procedure could be useful as an adjunct in studies of the geographica

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560106

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIn Finland all agricultural multinutrient fertilisers have been supplemented with sodium selenate since 1984 in order to increase the selenium (Se) content of domestic foods and to raise the population's low Se intake. In the present study the Se contents of 125 food items, most of them produced locally but some imported, have been analysed using electrothermal atomic absorption spectrophotometry. The quality of Se analyses was verified by accuracy and precision measures of certified references and non‐certified controls. In all cases the Se‐supplemented fertilisation increased the Se levels of domestic agricultural products. The mean Se values (mg kg−1dry weight) in different food groups varied as follows: cereals 0.05–0.35; vegetables and fruit<0.01,–1.20; meat and meat products 0.16–4.90; fish 0.54–3.80; dairy products and eggs 0.05–1.30; and ready to eat foods 0.04–0.78. The highest Se contents were in kidney, liver and roe whereas the lowest concentrations were found in some fruits and berries. Generally, foods of high protein content, such as meat, fish and high protein dairy products, were abundant sources of Se. The present Se intake, calculated according to Finnish national food statistics and the present results, is about 0.11 mg day−1at an energy level of 10 MJ (2400 keal). Cereals, meat, dairy products, eggs and fish, respectively, contributed 26%, 29%, 20%, 10% and 9% of the total intake. The Se intake now very probably meets the recommendations. Only diets with a very exceptional composition provide less than 0.05 mg or more th

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560107

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe psychrotrophic count and pH of unacidified pea tempeh increased during storage at 4°C and the product was not acceptable after 1 week's storage. Acidification of pea during soaking did not markedly improve the keeping quality of the product. Inoculation of cooked pea with Lactobacillus plantarum resulted in a product with better keeping quality. Unacidified and acidified chickpea tempeh did not spoil within 2 weeks' storage. Inoculation with L plantarum resulted in a product which did not spoil within 3 weeks' storage. Micrococcus and Bacillus spp dominated the flora during storage. Bacillus pumilus was the most frequently isolated Bacillus sp, and the most frequently isolated Micrococcus sp was M varians

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560108

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe effect of the method of olive oil extraction on the total polyphenol, 1,2‐diphenol content and stability of the oil was studied. The total polyphenol and 12,‐diphenol content of oils extracted in commercial olive oil mills was 60% and 45% lower, respectively, than oil extracted on the laboratory scale. A significant difference was found in total polyphenol content between oils obtained by traditional press systems and new continuous systems. The stability of the industrially extracted oil was considerably lower on account of its reduced phenol cont

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560109

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe present work describes a method for the determination of free and total sulphite in fresh sausages and its implementation on 48 samples. The method includes the extraction of sulphite, both free and total, by dissolution of the sample in a suitable solvent and determination by high performance liquid chromatography with electrochemical detection. The method is that previously reported by Kim and Kim (J Food Sci 51 1986 1360–1361) improved by certain modifications the principal of which consists of working atpH 10 for the extraction of total sulphite. Use of this pH permits reversible dissociation of the combined sulphite. In reproducibility assays carried out on sausages, variation coefficients of 3.3 and 5% were obtained for free and total sulphite, respectively. To evaluate recovery, sulphite was added to the samples as hydroxymethylsulphonate. Mean recovery was 86.4% with a variation coefficient of 3.8%.In 62% of the sausages analysed, amounts of total sulphites higher than 450 μ SO2g−1were found. Among the samples, considerable variation was observed in the distribution of sulphite between the free and combined f

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560110

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0022-5142    

DOI:10.1002/jsfa.2740560111

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY