The defensive reaction of apple cultivar Idared (Malus domestica Borkh.) was studied after inoculation with three different pathogens (Penicillium expansum, Monilinia fructigena, and Gloeosporium spp.). Changes in phenolic content and activity of phenylalanine-ammonia lyase were determined after 7, 14, and 21 days after the inoculation. The significant differences were discovered in the progress of rotting after the inoculation. The increase in phenols concentration and in phenylalanine-ammonia lyase activity varied in the place of fungal attack, in the tissues around rotten zone and in the healthy part. The response to the infection was different in the fruit peel and flesh. Very good correlation was found between the activity of phenylalanine-ammonia lyase and total phenol content (r = 0.76–0.98).

Upon the completion of a three-year evaluation of natural occurrence of storage diseases within a range of cultivars or advanced selections and a simultaneous assessment of their other characteristics, an apple ideotype has been proposed that could be used in breeding of new cultivars resistant to these diseases. The ideotype combines the potential of apples for long-term storage with higher skin thickness and toughness, a lower production of ethylene, a higher natural content of calcium, a higher content of total phenolic compounds and antioxidant capacity, a higher flesh firmness, and a higher acidity of juice expressed in pH values. For some of these characteristics, threshold values have been suggested in the paper. The genotypes preselected according to these criteria should be chosen on the basis of the final screening with Pezicula alba inoculum test. The result of the inoculation test should be equal to or better than the standard cultivar Gala. Future research is required to determine the feasibility of the ideotype in routine breeding programs.

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During the last three seasons the specific softening of pickled cucumbers was observed. The defective samples were analysed, but no microbial contamination was confirmed and no residual enzyme activity as well. The hypothesis of residual activity of microbial pectinases and cellulases as the most probable softening cause was proposed. The cellulolytic and pectolytic activities of nineteen strains of moulds and yeasts isolated from the samples of soils, cucumbers and cucumber plants rests were compared. The inactivation parameters (D and z values) of pectolytic enzymes of the most active strains were determined. The inhibitory effect of Ca 2+ addition was evaluated within the model experiments. The residual enzyme activities were confirmed as the main cause of the defect, together with other factors such as the characteristic composition of microbial contamination, the stress or other damage of the cucumbers during the postharvest manipulation (chilling injury, humidity stress, etc.), microbial contamination of cucumbers before processing, conditions of washing, heat treatment parameters, etc. The practical recommendations for the prevention of the defect were formulated.Keywords: cucumbers; effect of Ca 2+ ; softening of sterilised vegetables; cellulolytic activity; pectolytic activity; mould Pasteurised cucumbers in acidic brine are one of the traditional Central European foodstuffs (e.g. Znojemské okurky and other brands). During the last three seasons the specific quality defect was observed. The products complied with specifications just after the production process (sorting, washing, pickling, sealing and pasteurisation) but after several months of storage the maceration of surface layers of cucumbers was observed. Similar phenomenon was described in fifties in the production of fermented cucumbers in brine, the softening was caused by fungal polygaracturonases and cellulases, which were introduced into the brine mainly by way of fungus laden flowers that remain attached to the green cucumbers (Raymond et al. 1959). Various inhibitory treatments including the use of plants rich in hydrolysable tannins (grape, persimmon, dog wood, blueberry, etc.) were described (Bell et al. 1962). Leafs of grapes are often used as a traditional part of the recipe also for the production of pasteurised pickled cucumbers, but more often the calcium is used to improve the texture. The mechanism of calcium effect is known and often studied, divalent cations form bonds with the dissociated free carboxyl groups of adjacent pectin molecules to form more rigid structure (e.g. Fleming et al. 1987). The firmness effect of calcium depends on the degree of pectin methylation and amount of calcium added (Hudson & Buescher 1986; Howard & Buescher 1990;Krall & McFeeters 1998), the hardening effect of calcium surprisingly increases with pH reduction, below pH 5 the relative effectiveness of calcium in reducing rate of softening increases as pH decreased (Hudson & Buescher 1985;McFeeters & Fleming 1989, 1990, 1991.The aim of this...

SummaryThe stability of apple puree at different constant temperatures (-18 "C, 4 "C, 20 "C, 50 "C and 60 "C) was studied within the period of 30 days. During this time changes in the samples of apple puree, which was stored at variable temperature, were determined as well. The content of ascorbic acid, the sucrose inversion, the formation of furfural and levulinic acid as well as sensory properties were followed as criteria of the puree quality. From obtained data the temperature dependence of these reactions was derived. On this base the shelf life of apple puree (the time, after which the sensory differences became significant) was estimated. This period was relatively short, i.e. less than 100 days at 20 "C. The changes in puree at variable temperature were similar to those at higher storage temperatures (40 "C -50 "C).