Fakultät Agrarwissenschaften

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Die Fakultät entwickelt in Lehre und Forschung nachhaltige Produktionstechniken der Agrar- und Ernährungswirtschaft. Sie erarbeitet Beiträge für den ländlichen Raum und zum Verbraucher-, Tier- und Umweltschutz.

Homepage: https://agrar.uni-hohenheim.de/

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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.
The effect of picking time and postharvest treatments on fruit quality of mango (Mangifera indica L.)
(2012) Vu, Hai Thanh; Wünsche, Jens Norbert
Mango production in Northern Vietnam is mainly in the upland areas. The two locally grown cultivars are ?Tron? and ?Hoi? with limited yearly production due to poor traditional crop management practices by ethnic minorities. Both cultivars possess excellent fruit aroma and taste properties, yet there is a need to further improve fresh fruit quality to meet high domestic demand and consumer expectations in the market place, thereby exploiting more products of preferred quality. Assessment of quality parameter and consumer preference can assist to precisely determine optimum harvest time and suitable storage regime for a given cultivar. Furthermore, specific postharvest treatments such as applications of hot water, 1-MCP or ethrel for manipulating fruit ripening and shelf-life may help to enhance economic returns and thus to make mango production in the long term more profitable. The research work on both cultivars was carried out on farmer orchards near the township of Yen Chau, Son La Province, Vietnam, in 2007, 2008 and 2009. The research objectives were to (1) monitor internal and external fruit quality changes in relation to varying select picks throughout the harvest period and to a range of storage temperatures; (2) investigate the effect of 1-MCP on various fruit ripening parameters for maintaining fruit quality and extending shelf-life; (3) evaluate applications of aqueous ethrel solution in cool storage for accelerating fruit ripening; and (4) assess the responses of several external fruit criteria to hot water treatments and subsequent cool storage. At each select pick, fruit was immediately taken to the laboratories at Hanoi University of Agriculture for fruit quality assessment at harvest, and following various postharvest treatments, ex-store. Chemical analyses of fruit tissue samples were performed at the University of Hohenheim. Various physicochemical quality parameters such as fruit weight, skin disorder, skin and flesh colour, flesh firmness, total soluble solids concentration, titrable acidity, as well as concentrations of soluble sugars, starch, vitamin C and carotenoids were evaluated. The results of the first part indicated that key quality criteria for determining the optimal harvest time of ?Tron? and ?Hoi? were determined. ?Hoi? fruit was at best quality when harvested late, preferably in the 2nd or 3rd pick, whereas 1st pick fruit was relatively immature with less than 8% total soluble solid concentration and did not properly ripen when stored at 12ºC. In contrast, ?Tron? fruit should be picked early in the harvest period since the 3rd pick with tree-ripened fruit was only suitable for direct local marketing without storage time. The results also indicated that ?Tron? fruit of the 1st and 2nd pick and ?Hoi? fruit of 2nd and 3rd pick continued the ripening process to full maturity when stored at 12ºC. Consequently, fruit from these picks were suitable for distant markets when handled within 5-10 days at 20ºC or up to 20 days at 12ºC. Generally, ?Hoi? had a greater postharvest potential than ?Tron? but ex-store fruit quality of both cultivars was best with flesh firmness ranging from 70.5 to 96.1 N, skin hue angle from 71.4º to 85.4º, flesh hue angle from 70.1º to 78.5º and total soluble solid concentration from 16.8 to 19.6%. The results of the second part clearly showed that 1-MCP is a useful tool to delay fruit ripening and in particular softening of both cultivars during the postharvest period. Both cultivars treated with 1000 nL?L-1 1-MCP delayed considerably the decrease in TA, skin and flesh hue angle as well as the loss of flesh firmness in the 1st and 2nd pick for about 10 days of storage at 12ºC compared to control. Both cultivars were more sensitive to 1-MCP applications in 1st rather than the 2nd pick. In addition, 1-MCP applications were more effective on ?Tron? fruit than ?Hoi? fruit. The results of the third part indicate that 0.8% ethrel accelerated fruit ripening on fruit from the 1st pick of both cultivars while stored at 12ºC. Ex-store fruit quality was acceptable and met consumer preference. The efficacy of ethrel application on ?Hoi? fruit was greater than that on ?Tron? fruit. The results of the fourth part showed that the degree of skin disorder was considerably decreased when ?Tron? and ?Hoi? fruit were treated with either 48ºC or 50ºC water for 6 min and stored at 12ºC. This treatment delayed skin colour development of ?Hoi? when compared to other treatments. In conclusion, this study demonstrates that lack of proper whole chain fruit quality management systems is the key factor for the limited production of mangoes in Northern Vietnam. Improved fruit quality management can result in more consistent and higher quality particularly for distant markets. Based on the results of this work, ?Tron? and ?Hoi? fruit should be harvested using well-defined and recommended harvest quality indices and thereafter undergo appropriate postharvest management systems to attain higher fruit quality. This will help farmers to better manipulate fruit ripening processes, to deliver high quality fruit to the market and to achieve greater returns and thus livelihoods.

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