Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.14/9740
Título: Modulation of aroma volatiles and phytochemical quality of fresh-cut melon (Cucumis melo L.) by oxygen levels, 1-methylcyclopropene and lysophosphatidylethanolameine
Autor: Amaro, Ana Luísa Leite Fernandes
Orientador: Almeida, Domingos Paulo Ferreira de
Data de Defesa: 18-Jul-2012
Resumo: Current fresh-cut technologies are effective in the effort of maintaining visual quality during the fresh-cut fruit supply chain. However, studies on extended shelf life based on appearance attributes or microbial stability have neglected the understanding of the effect of processing technologies and conservation techniques in the aromatic, nutritional, and functional properties of processed fruit. Three technologies were evaluated for their effects on quality of fresh-cut melon, with emphasis on aroma volatiles: oxygen levels, the ethylene action inhibitor 1-methylcyclopropene (1-MCP), and lysophosphatidylethanolamine (LPE), an inhibitor of phospholipase D (PLD). Modified atmosphere packaging (MAP) is widely used in fresh-cut fruit, with the objective of extending shelf-life. Nevertheless, MAP requirements and recommendations for fresh-cut fruit target mostly color and texture maintenance, neglecting the effects on aroma production. In this thesis, the quality attributes and aroma production of fresh-cut melon were monitored during MAP storage. Cantaloupe and honeydew melon cultivars were processed into cubes and stored at 5 ºC under high passive MAP or reduced controlled atmosphere (CA; 5 kPa O2 + 10 kPa CO2, balance N2). Oxygen levels during storage had a greater impact on aroma than on other quality attributes during storage of fresh-cut climacteric and non-climacteric melon. Cantaloupe and honeydew melon flavor-important volatiles were differently affected by oxygen levels inside the packages. Also, storage time had a significant effect on volatile production of fresh-cut cantaloupe and honeydew melons. 1-MCP application to whole fruit, its effects on quality, ethylene production and perception have been the subject of many studies. In contrast, fewer studies have focused on 1-MCP application to fresh-cut fruit. For its known inhibitory effect on ethylene production, we anticipated 1-MCP to have beneficial effects on some quality attributes of fresh-cut melon, while altering aroma profile. The effect of 1-MCP application in quality and synthesis of flavor-important volatile compounds in melon was evaluated during storage of fresh-cut cantaloupe. Cantaloupe melons were processed and treated with 1.0 μL L-1 of 1-MCP, for 24 h at 5 ºC, packaged in vented plastic clamshells and stored under normal atmosphere at 5 ºC for 9 days. Treatment with 1-MCP did not affect the main quality attributes of fresh-cut melon, but affected nine of the flavor-important volatiles, particularly those with isoleucine and phenylalanine as precursors. 1-MCP affected fresh-cut cantaloupe production of propyl acetate, 2-methylbutyl acetate, methyl butanoate, methyl 2-methyl butanoate, methyl hexanoate, 2-methylbutyl alcohol, phenethyl alcohol, benzyl alcohol and heptanal. LPE is reported to inhibit PLD activity, reduce ethylene production, and extend shelf-life of many horticultural commodities. Therefore, LPE could provide a novel treatment to improve the quality of fresh-cut fruit, via maintenance of membrane integrity and reduction of the wound response. The effect of LPE on PLD activity, quality and volatile production of fresh-cut melon was investigated during storage. Charentais-type melons were processed into cubes and vacuum-infiltrated with 200 mg L-1 of LPE, packaged in plastic clamshells and stored at 5 ºC for 9 days. LPE was not effective in maintaining overall quality of fresh-cut melon but induced a reduction of aldehydes production in the first three days of storage. LPE inhibited PLD activity in the first day after processing, which may have induced the reduction of aldehydes observed at day three of storage of fresh-cut melon. In conclusion, oxygen levels significantly affect the volatile profile of fresh-cut melon, and there may be opportunity to optimize oxygen recommendation for aroma preservation. 1-MCP and LPE altered the volatile profile of fresh-cut melon but had minimal or no effect on other quality attributes.
URI: http://hdl.handle.net/10400.14/9740
Aparece nas colecções:R - Teses de Doutoramento / Doctoral Theses
ESB - Teses de Doutoramento / Doctoral Theses

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