Functional characterization of a melon alcohol acyl-transferase gene family involved in the biosynthesis of ester volatiles. Identification of the crucial role of a threonine residue for enzyme activity

Volatile esters, a major class of compounds contributing to the aroma of many fruit, are synthesized by alcohol acyl-transferases (AAT). We demonstrate here that, in Charentais melon (Cucumis melo var. cantalupensis), AAT are encoded by a gene family of at least four members with amino acid identity ranging from 84% (Cm-AAT1/Cm-AAT2) and 58% (Cm-AAT1/Cm-AAT3) to only 22% (Cm-AAT1/Cm-AAT4). All encoded proteins, except Cm-AAT2, were enzymatically active upon expression in yeast and show differential substrate preferences. Cm-AAT1 protein produces a wide range of short and long-chain acyl esters but has strong preference for the formation of E-2-hexenyl acetate and hexyl hexanoate. Cm-AAT3 also accepts a wide range of substrates but with very strong preference for producing benzyl acetate. Cm-AAT4 is almost exclusively devoted to the formation of acetates, with strong preference for cinnamoyl acetate. Site directed mutagenesis demonstrated that the failure of Cm-AAT2 to produce volatile esters is related to the presence of a 268-alanine residue instead of threonine as in all active AAT proteins. Mutating 268-A into 268-T of Cm-AAT2 restored enzyme activity, while mutating 268-T into 268-A abolished activity of Cm-AAT1. Activities of all three proteins measured with the prefered substrates sharply increase during fruit ripening. The expression of all Cm-AAT genes is up-regulated during ripening and inhibited in antisense ACC oxidase melons and in fruit treated with the ethylene antagonist 1-methylcyclopropene (1-MCP), indicating a positive regulation by ethylene. The data presented in this work suggest that the multiplicity of AAT genes accounts for the great diversity of esters formed in melon

Uso de cera de carnaúba e saco plástico poliolefínico na conservação pós-colheita do maracujá-amarelo Use of carnauba wax and plastic film on postharvest conservation of the yellow passion fruit

A alta perecibilidade do maracujá-amarelo reduz sua vida de prateleira limitando sua comercialização. Este trabalho teve por objetivo aumentar a conservação pós-colheita do maracujá-amarelo pelo uso de cera e saco plástico poliolefínico. Os frutos, após colhidos, selecionados, lavados e desinfestados com hipoclorito a 1%, foram submetidos aos tratamentos: 1-imersão em cera de carnaúba (Fruit wax®), diluída na proporção 1:4 (m/v); 2 embalagem em saco plástico poliolefínico com 0,015 mm; 3 associação entre a imersão na cera de carnaúba e embalagem plástica; 4 testemunha, onde os frutos foram imersos em água com hipoclorito a 1%. Foram feitas análises da porcentagem de perda de matéria fresca, do teor relativo de água na casca, de sólidos solúveis, da acidez titulável, da relação sólidos solúveis/acidez titulável da polpa, das porcentagens de casca e polpa, e da relação casca/polpa. Houve menor porcentagem de perda de matéria fresca ao utilizar os tratamentos 2 e 3 ao longo do período de armazenamento. Entretanto, não houve diferença entre os tratamentos com relação à matéria fresca do fruto, casca e polpa, havendo redução destas variáveis durante o período de armazenamento. Também não houve diferença com relação às porcentagens de casca e de polpa, e relação polpa/casca, sendo que a primeira reduziu, e as duas seguintes aumentaram no armazenamento. Em geral, houve redução dos sólidos solúveis e da acidez.<br>The high perishability of the yellow passion fruit reduce its postharvest conservation and availability, mainly for "in natura" consumption. This work objectified to increase the postharvest life of the yellow passion fruit by using wax emulsion and plastic film. After harvest, the fruits were selected, washed, disinfested and submitted to the treatments: 1, immersion in Fruit Wax®; 2, packing in plastic film; 3, immersion in Fruit Wax® and packing plastic film and 4, control, fruits were immerged in water. The fruits were conditioned in trays and stored in ambient conditions. There were smaller percentage of fresh matter loss and larger water relative tenor when using the treatments two and three in the storage course. However there was no difference among the treatments regarding fresh matter of the fruit, peel and pulp having reduction in the course of storage. There was no difference in the relation of peel percentages and of pulp and pulp/peel relationship and the first reduced and following two increased in the storage. In general, there was total soluble solids and acidity reduction

Conservação de goiabas tratadas com emulsões de cera de carnaúba Postharvest conservation of guavas through carnauba wax emulsion applications

A goiaba é um fruto muito perecível. Assim, objetivou-se avaliar os efeitos de ceras à base de carnaúba na conservação pós-colheita de goiabas Pedro Sato sob condição ambiente. Utilizaram-se cinco ceras comerciais: Citrosol AK (18%), Citrosol M (10%), Fruit wax (18 a 21%), Meghwax ECF-100 (30%) e Cleantex wax (18,5 a 20,5%), as quais foram aplicadas manualmente, na proporção de 0,15 a 0,20mL por fruta. Frutas sem aplicação de cera foram utilizadas como controle. O delineamento experimental foi inteiramente casualizado com 6 tratamentos, 4 repetições e 5 frutas por parcela. As goiabas foram caracterizadas imediatamente após a colheita e avaliadas aos 2, 4 e 6 dias após a aplicação dos tratamentos. As ceras exerceram pouca influência nos teores de sólidos solúveis totais, acidez total titulável e ácido ascórbico, porém, foram eficientes em retardar o amadurecimento, reduzir a perda de massa e a incidência de podridões. A cera Meghwax ECF-100 apresenta potencial para utilização em goiabas, porém há necessidade de ser avaliada em maior diluição, para evitar alterações indesejáveis.<br>Guavas are very perishable fruits. Therefore, the objective of the present work was to evaluate the effects of several carnauba based waxes in the postharvest life of Pedro Sato guavas under room conditions. Five commercial waxes were used: Citrosol AK (18%), Citrosol M (10%), Fruit wax (18 a 21%), Meghwax ECF-100 (30%) e Cleantex wax (18,5 a 20,5%). The waxes were applied manualy in the rate of 0.15 to 0.20mL of wax per fruit. Control fruits were not treated. The experiment was conducted in a completely randomized design with 6 treatments, 4 replicates per treatment and 5 fruits as experimental unit. Guavas were evaluated at harvest and at every 2 days until the 6th day after treatments. Waxing had little effect on total soluble solids, total titratable acidity and ascorbic acid contents. However, the waxes were efficient in delaying ripening and reducing mass loss and decay incidence. The Meghwax ECF-100 shows potential for its use in guavas, although it needs to be tested in lower concentrations to avoid ripening problems

Caracterização físico-química de frutos de quatro cultivares de quiabo Physical and chemical characteristics from fruits of four okra cultivars

Efetuou-se a caracterização físico-química dos frutos de quatro cultivares de quiabo neste estudo. O delineamento utilizado foi de blocos casualizados, sendo os tratamentos constituídos pelas cultivares Amarelinho, Red Velvet, Star of David e Mammoth Spinless, com cinco repetições. Na maturidade comercial os frutos da cultivar Star of David tiveram maior diâmetro, peso fresco total e teor de matéria seca, menor comprimento, teor de umidade e de vitamina C comparado com as demais cultivares. A cultivar Red Velvet teve o menor diâmetro, peso fresco, teor de matéria seca, açúcares redutores e teores de clorofilas a, b e total, e maior teor de umidade e vitamina C. Frutos da cultivar Mammoth Spinless apresentaram os maiores teores de clorofilas a, b e total. A cultivar Amarelinho teve maior comprimento e menores teores de clorofila, a, b e total. As cultivares Amarelinho e Mammoth Spinless apresentaram maiores teores de açúcares redutores.<br>In an experiment some physical and chemical characteristics of four okra cultivars were evaluated. The experimental design was of randomized blocks, where the treatments were the cultivars Amarelinho, Red Velvet, Star of David and Mammoth Spinless with five replications. At commercial maturity fruits of the cultivar Star of David presented the largest diameter, total fresh matter, content of dry matter, smallest length, content of water and vitamin C in comparison to the other cultivars. The cultivar Red Velvet presented the smallest diameter, total fresh matter, content of dry matter, reducing sugars and content of chlorophyll a, b and total, but the largest content of water and vitamin C. The cultivar Amarelinho produced the longest fruits and the smallest content of chlorophyll a, b and total. The cultivars Amarelinho and Mammoth Spinless showed higher contents of total reducing sugars