Characterisation of 32 cultivars of Phaseolus vulgaris has been obtained by densitograms of protein patterns, which were evaluated by starch‐gel electrophoresis of protein fractions obtained by single extraction of bean seeds with water. Experiments indicated that the protein patterns are unlikely to be affected by external conditions such as N fertilisation, climatic conditions and soil properties.
Sensory evaluation and quantitative analyses of catalase, peroxidase and lipoxygenase were performed in frozen Brussels sprouts during storage at three different temperatures. Within 6 weeks at -4°C all sensory attributes had reached the limit of acceptability , while peroxidase activity increased in the same period. At the end of this period catalase activity had increased strongly. Colour and flavour decreased slowly during 11 months storage at -9"C, while texture remained on a constant level. After 4 months at -9°C a slight catalase activity became detectable. At -18°C no detectable changes occurred during 1 1 months. Characterization of the preliminary blanching process in terms of residual activities of peroxidase and catalase remains possible after prolonged storage, provided microbial growth can be excluded.
Changes in starch content and amylase zymograms were followed during storage of Golden Delicious and Cox's Orange Pippin apples. Although the former was stored at 3-4 degrees C under controlled atmosphere (3--4% O2; 7--8% CO2 by volume) and the latter in air at 17 degrees C, in both, the multiple forms of amylases remained active, even after the starch content decreased to zero. It is the lack of starch substrate, therefore, rather than of enzymes that limits the amylase action in the stored apple.
Pure cultures of five microbial species were used to test the formation of exopolysaccharides (EPS) when grown in agitated sucrose (5% w/v) containing liquid cultures. These test species were isolated from stems of freshly harvested cut flowers (Chrysanthemum, Gerbera and Rosa) or from the vase water of these flower cultivars. The partial conversion of sucrose into other saccharides was demonstrated by HPLC and colorimetric analysis. The final polymeric character of the newly formed saccharides was investigated. SEM preparations of xylem vessels of Rosa maintained in EPS‐containing vase water showed blockage, disorganization and injury of the vessel structure. EPS were shown not to pass the xylem pit membranes. Recovery from the first symptoms of disturbed water flow (wilting) due to EPS was possible in young flowers by cutting off the blocked part of the stem (15–20 cm. The higher the microbial conversion rate of sucrose into polysaccharides, the more disturbed were the water relations of the roses placed in the EPS‐containing fluid, as was demonstrated by the decrease of: (1) water conductivity of Rosa stem segments (ml/30 min); (2) water uptake (ml/d); (3) Rosa vase life (d); and (4) flower bud development. Bacterial EPS (presumably levans and dextrans) could be concentrated in the retentate by molecular filtration with a cut‐off level of 10000 Da. Filtrates did not cause Rosa xylem blockage and ‘bent‐neck’of the flower stems, but still may be toxic to roses. Two simple methods were also used for diagnostic investigations: (1) the beetroot tissue cube test to detect microbial products causing injury of the plant cell membranes, (2) the acid fuchsin test, to show the extent and location of Rosa xylem vessel occlusion.
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