Browsing by Person "Vu, Hai Thanh"

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    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.