Browsing by Subject "Nachernteverfahren"

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    Physiological responses of 'Jonagold' apple (Malus domestica Borkh.) following postharvest 1-Methylcyclopropene (1-MCP) application
    (2009) Heyn, Claudia Susanne; Wünsche, Jens Norbert
    Storage technologies such as controlled atmosphere (CA) storage and recently 1-Methylcyclopropene (1-MCP) treatments have led to an all-year-round global supply of high qualitative apple fruit. As a consequence, pressure of competition between several apple growing areas is increasing and in the same way consumers demands and expectations for apple fruit quality. However, throughout storage fruit quality is generally preserved at a high level whereas conditions at several points throughout the distribution chain are often not adequate for fresh commodities. It is critically important to maintain consistently high fruit quality throughout the marketing period to the final consumer and that fruit quality at the point of sale meets consumer requirements. Although decision for purchasing apple fruit is mainly due to appearance and firmness, consumer are increasingly concerned about nutritional quality and health-protecting compounds in foods. The plant hormone ethylene influences many of the ripening processes in climacteric fruit such as apple. Several storage conditions, such as reduced storage temperatures, controlled storage atmospheres with low O2- and elevated CO2-concentrations and recently 1-MCP treatments are known methods to minimize ethylene biosynthesis, ethylene sensitivity and responses of harvested climacteric fruit and by that to slow metabolic changes during ripening. 1-MCP is an effective tool for maintaining fruit quality during storage and post-storage handling. 1-MCP, a synthetic unsaturated cyclic olefin, is thought to act as a competitive substance to ethylene, occupying the ethylene receptor site so that ethylene cannot bind. In general, 1-MCP is able to counteract ripening effects triggered by ethylene during and after storage by blocking its action in fruit rather than inhibiting its production. The present research project consists of three studies. The aim of the first study was to determine the effect of 1-MCP treatment, storage condition and ?duration on apple fruit quality and consumer acceptability. The second part of the study focused on the effect of 1-MCP treatment, storage condition and ?duration on climacteric characteristics of apple fruit. The effect of 1-MCP treatment, storage condition and ?duration on antioxidant capacity of apple fruit was studied in the third part of the research. ?Jonagold? apple fruit were picked at commercial maturity in 2004, 2005 and 2006. Fruit were treated with 1-MCP on the day of harvest (0 days after harvest, 0 DAH) in 2004 and 7 DAH in 2005 and 2006 and stored the following day either in cold storage, CA- or ultra low oxygen- (ULO) storage. Fruit was held in cold storage prior to commencement of storage in 2005 and 2006. After 2, 4 and 6 months in 2004/05, 3, 6 and 9 months in 2005/06 and 3 and 5 months in 2006/07 fruit samples from each storage atmosphere ± 1-MCP were removed. Fruit quality parameters were assessed after harvest, commencement of storage and after each sample removal in 2004/05, 2005/06 and 2006/07 following 10 days shelf-life at 20°C. Consumer preference mapping was performed after 3 and 5 months of cold- and ULO-storage in 2006/07. Shelf-life respiration rate and fruit ethylene production was measured after harvest, commencement of storage and after each sample removal in 2004/05 and 2005/06, respectively. In 2005/06 ATP and ADP concentration was additionally determined. Nutritional quality and health-protecting compounds were examined by means of ascorbic acid concentration (L-AA), phenolic compounds and total non-enzymatic antioxidant capacity in 2005/06 following 10 days shelf-life after harvest, commencement of storage and after each sample removal. The results of the first part of the study showed that fruit quality generally decreased during storage and shelf-life depending on 1-MCP treatments, storage condition and ?duration. However, 1-MCP delayed ripening more and maintained fruit quality better than CA- or even ULO-storage alone. In consumer preference mapping most consumers, regardless of age or gender, preferred the 1-MCP treated fruit from ULO-storage. This effect was particularly seen when fruit were stored longer. Though sensory evaluation studies are time-consuming and there might be some flaws and difficulties to generate representative results from consumer taste panels, they are a useful tool to assess food quality and consumer preference. The results of the second part of the study proved that 1-MCP is a potent antagonist in terms of reducing and delaying ethylene production and respiratory rise. Although CA- and ULO-storage reduced ethylene production significantly in ?Jonagold? apples, 1-MCP treatment inhibited ethylene biosynthesis and accompanied respiration rate more than CA- and ULO-storage alone. The present study clearly shows that apple fruit shall be exposed as soon as possible to 1-MCP treatment and appropriate storage conditions after harvest for achieving a maximum effect on reduction of climacteric characteristics and maintenance of postharvest and post-storage apple fruit quality. L-AA concentration significantly decreased during storage, irrespective of storage condition and 1-MCP treatment. At commencement of storage L-AA concentration in 1-MCP treated fruit was higher than in untreated control fruit. However, following 9 months of storage L-AA concentration was lower in all 1-MCP treated fruit when compared with untreated fruit. Vitamin C equivalent phenolic concentration and vitamin C equivalent antioxidant capacity (VCEAC) decreased after 6 months of storage and gradually increased again after 9 months of storage. 1-MCP treatment had no effect on phenolics and VCEAC, respectively. In general, the results of the third part of the study showed that the nutritional value of apple fruit was not influenced by 1-MCP and storage condition.
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    Plasma als Nacherntebehandlung gegen Monilinia spp. auf Zwetschge
    (2016) Fütterer, Julia; Vögele, Ralf
    In the scope of this project, the principle suitability of plasma as a postharvest treatment against Monilinia spp. on plum was surveyed. The plasma was generated using a microwave driven plasma torch at atmospheric pressure using air as process gas. Representing the three main Monilinia species in pomiculture (M. laxa, M. fructigena and M. fructicola), M. laxa was used as model organism for all experiments. Both spores and mycelium were attempted to be inactivated by plasma treatment. For a simplified experimental procedure, agar plates were used as model substrates. To show a possible practical implementation of the technique, plums were also plasma treated with the aim of showing the efficacy on the fruit and possible effects on several fruit quality parameters. After plasma treatment duration of 5 minutes, a significant reduction of M. laxa mycelium could already be shown. After 10 minutes of plasma treatment, a reduction of more than 90 % could be achieved. Thereby a characteristic three-phase course of the inactivation slope was observed. In contrast to these results, spores of M. laxa were proven to be more resistant. Even after 10 minutes of plasma application, no significant reduction of spore germination could be achieved. During the plasma treatments a heating of the substrates could not be avoided. The agar plates used as model substrates thereby showed a good thermal capacity. In contrast, plums had to be cooled in advance to avoid the melting of the wax layer of the fruit cuticle. For the artificial inoculation of plums the fruit cuticle was wounded to enable the pathogen to penetrate into the fruit flesh. As the inoculum cannot be reached by the superficial acting components of the plasma inside the fruit, the plasma treatment was not effective against fruit infections. To investigate a possible effect of the plasma treatment on fruit quality, skin colour, fruit flesh density as well as the content of sugar, acids, ascorbic acid and polyphenols were analysed. The results did not show any significant effects in comparison to untreated control fruit. By shielding mycelium on agar plates from plasma radicals using MgF2 platelets as filters during the treatment, it could be shown that the plasma effects are based on synergy of UV-radiation and radicals. The results show that the described method needs a very precise development and adjustment on the pathogen and the substrate. For example, the plasma effect on spores could be improved by appropriate modification of the plasma parameters. However, the effects on mycelia of M. laxa and the protection of the fruit quality parameters have shown a general practicability.