摘要:

AbstractResults are presented giving details of the effect of six different methods of sample preparation on the free radical concentration in irradiated chicken drumsticks. Comparisons were made using electron spin resonance spectroscopy. Freeze drying and grinding was found to be the preferred method of sample preparation.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480302

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractTwo‐hundred pairs of chicken bones (drumsticks) were irradiated at 2.5, 5.0, 7.5 and 10.0 kGy and stored for 0, 7, 14, 21 and 28 days at −20°C or + 5°C thus giving five replicates per treatment. Five unirradiated pairs of bones were stored at 5°C, one sample being analysed at each storage time. The samples were fragmented, freeze dried and ground prior to determination of the free radical concentration using electron spin resonance (ESR) spectroscopy. ESR signal strength increased significantly as irradiation dose increased, and decreased with storage time. Temperature alone had no significant effect on free radical concentration but, as the storage time increased, the bones stored at 5°C showed a significantly greater reduction in free radical concentration than those stored at −20°C. Correction of the ESR signal to a standard P or Ca concentration did not significantly reduce the variability of the results but did eliminate the interaction between storage temperature and st

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480303

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractTwenty‐one cultivars of sour orange (Citrus aurantiumL) and relatives selected in different areas of Spain were studied. Morphological determinations were carried out both in leaves and in fruits, including leaf size and area, number of oil glands, petiole length, fruit weight, number of seeds and others. Biochemical analysis included electrophoretic separations of proteins from leaves and fruit rind as well as peroxidases and esterases from some of the organs. Also chromatographic separations of rind oils were carried out in mature fruits. Quantitative and qualitative differences were detected for some of the cultivars. Enzyme differences were found to be adequate for distinction at the specific level. Two of the cultivars, ‘Bergamot’ and ‘Amargo clementino’, segregate from the main group, which indicates their belonging to a different species or to a hybrid. The validity of the present determinations for distinction and characterisation of material to be included in a citrus germplasm bank is

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480304

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractIn Malaysia, pulp preconditioning by post‐harvest storage of cocoa pods leads to the reduction of nib acidification during subsequent fermentation, reduction of the acid note and an increase in cocoa flavour in the resulting raw cocoa. Data from several shallow‐box fermentations, with material from unstored and stored pods, are compared and interpreted, obtained in the years 1984 to 1987 in a cooperational investigation of the Malaysian Agricultural Research and Development Institute (MARDI), Malaysia, and the Botanical Institute, Technical University of Braunschweig (TUBS), FRG. Prior to and during fermentation, pulp volume and pulp sugars; pH value, acetic acid and lactic acid content in the pulp and nibs; and oxygen concentration and temperature in the mass were determined. Some flavour assessments from selected samples are given. The great reduction in pulp volume per seed rather than the decrease of pulp sugars per seed during pod storage was found to be of the most importance. Pulp‐volume reduction enhances mass aeration and increases the ratio of respiration to ethanol fermentation and its subsequent oxidation to acetic acid. As a consequence, the acidification of the seeds during the formative stages of flavour precursors (after the death of the seeds) is strongly reduced. With effectively dry stored pods (pulp volume per gram of seed ≤0·6 ml) the anaerobic phase during the initial stages of fermentation which is common with unstored pods is suppressed. Under these conditions the nib pH value does not fall below 5·0 and no drastic acid (and flavour) degradation at the end of fermentation is necessary to reduce the acidity in

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480305

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractUnretted and retted bark and stem ofCorchorus olitoriusL and retted stem of C capsularis L, two species of jute, were analysed for ash, lignin, low molecular weight carbohydrates and polysaccharides. The results are compared with those fromCcapsularis published earlier. The unretted bark and stem ofColitorius contained less low molecular weight carbohydrates than the corresponding fractions ofCcapsularis.Colitorius bark contained less cellulose and more hemicellulose thanCcapsularis, particularly after retting. Xylans isolated from the retted fibre and stem ofColitorius were found to have a similar composition to those from C capsularis.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480306

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSoluble degraded lignin complexes (LCs) were prepared using a two‐step incubation with buffered rumen fluid, and isolation of the LC from the latter liquid phase by filtration, dialysis and freeze drying. The yields of crude LC were 19 and 10 g kg−1of initial dry matter for wheat straw (Triticum arvenseL cv Holme) and red clover (Trifolium pratenseL cv Hermes II) stems, respectively. Gel permeation chromatography of both LCs showed similar patterns with about 95% of the material having a molecular weight of 12 000 to 16 000 when compared with dextran standards. The total content of carbohydrates in the complexes was 82 g kg−1DM in wheat straw LC and 50 g kg−1DM in red clover stem LC. Uronic acid and arabinose residues dominated both species with xylose, galactose and glucose as important residues in wheat straw LC and galactose and glucose residues in red clover stem LC. The lignin content estimated by the acetyl bromide method was 328 g kg−1DM in wheat straw LC and 139 g kg−1DM in red clover stem LC, and nitrobenzene oxidation of both LCs yielded vanillin and syringic aldehyde in approximately equal amounts. NMR spectroscopy gave glycosidic, but not aromatic, signals, and ESR spectroscopy indicated the presence of stab

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480307

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis study examined the effects of packaging on the sensory qualities of two cooked chilled foods (deep fried chicken drumsticks and chicken à la king) after extended chilled storage. Quantitative descriptive analysis was used with a trained taste panel to score the sensory attributes of the two products at various stages of chilled storage up to a maximum of 14 days at 0–3°C.Storage had a significantly (P<0·05) deleterious effect on all the sensory attributes of chicken drumsticks. Just over half the sensory characteristics of chicken à la king were significantly affected and these effects were mainly concerned with appearance. Vacuum and modified atmosphere packaging extended the shelf life of both products in the sense that the changes in sensory attributes after 11–14 days were the same as in the cling‐film‐wrapped products after 4 days. The vacuum and modified atmosphere treatments were almost indistinguishable in their effects on the sensory

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480308

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe free and bound lipid content, and the fatty acid composition of these lipids, in 11 oat (Avena sativaL) cultivars grown in three Australian states were determined. There were significant differences between cultivars in both the free and bound lipid content and in the proportion of fatty acids in these lipids. The proportion of linolenic acid in the lipids of some oat cultivars grown in Western and South Australia was greater than that in the same cultivars grown in Victoria. There was a positive correlation between the free lipid content and the proportion of linoleic acid in the Swan cultivar.

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480309

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractLamb muscle contained 0.4 mg glutathione S‐transferase (EC 2.5.1.18) per gram of tissue. On storage at 1°C, 20% of the activity was lost after 3 weeks. Glutathione S‐transferase was isolated from lamb muscle by affinity chromatography on S‐hexyglutathione Sepharose 6B. One major form of the enzyme was present in the purified preparation, a dimer with subunit molecular weight of 22 900 and isoelectric point of 6.7. This enzyme fits into the Pi class on the basis of substrate specificity. Linoleic acid hydroperoxides and trans, trans‐2,4‐decadienal, products of linoleate peroxidation, were both substrates (0.11 and 0.24 μmol min−1mg−1protein respectively). Glutathione S‐transferase inhibited copper‐stimulated peroxidation of arachidonate in the presence of glutathione. The inhibition was only slightly less efficient in the absence of glutathione. The latter effect probably arises from the presence of enzyme‐bound glutathione (4–5 mol mol−1enzyme subunit) and also from a small but significant glutathione‐independent peroxidase activity. The latter was detected using an HPLC assay which monitors formation of product directly. Reduced glutathione per se showed only a slight inhibition o

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480310

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractOne of the causes of organoleptic changes in milk, lipid peroxidation, has been monitored by a sensitive assay newly applied to foodstuffs. It has been shown that even at medium radiation doses (up to 3600 Gy) negligible lipid peroxidation takes place, providing the milk is thoroughly gassed with nitrogen. Using a test spoilage microorganism, Pseudomonas aeruginosa (Schroeter), it was shown that the D10was 35 Gy in air and 105 Gy under anaerobic conditions. Dose/survival curves indicate that 5 decades of killing needed 200 Gy in air and 600 Gy under nitrogen. However, even after receiving a dose of 1600 Gy, both aerobically and anaerobically treated milk failed the methylene blue test at 21 days post‐irradiation. The data indicate that, although the deleterious lipid peroxidation effects of irradiation can be minimised by the removal of air, this in turn results in a degree of protection being afforded to the bacteria, and that doses in excess of 1600 Gy are needed to effectively sterilise mil

ISSN:0022-5142    

DOI:10.1002/jsfa.2740480311

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY