dissertação
Parede celular: análises do mecanismo de perda de firmeza de goiabas cv. Pedro Sato durante o amadurecimento em temperatura ambiente
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UNIVERSIDADE FEDERAL DE LAVRAS
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Programa de Pós-Graduação
DQI - Departamento de Química
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Áreas Temáticas da Extenção
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Resumo
A goiaba é considerada um fruto bastante atrativo, em razão de sua cor e
agradável aroma, além de ser uma das mais completas e equilibradas frutas no
que diz respeito ao valor nutritivo, contendo alto teor de vitamina C, quantidades
razoáveis de vitaminas A e B e sais minerais, como cálcio, fósforo e ferro.
Devido ao seu intenso metabolismo durante o amadurecimento, a goiaba é um
fruto altamente perecível, com uma vida útil que pode chegar de três até cinco
dias sob temperatura ambiente. A firmeza dos frutos verdes e maturos está
relacionada principalmente aos polímeros de pectina. A perda de firmeza
durante o amadurecimento de goiaba é devido à atividade de enzimas
hidrolíticas, que promovem intensa solubilização das pectinas constituintes da
parede celular. Diante do exposto, com a finalidade de tentar explicar a rápida
diminuição da firmeza, investigou-se a composição da parede celular da goiaba,
as interligações entre suas cadeias e os compostos fenólicos ligados, bem como
os processos enzimáticos envolvidos na liberação e transporte dos polímeros de
pectina para o interior da célula. Goiabas foram colhidas no estádio “de vez” e
armazenadas por oito dias a uma temperatura de 27º ± 1ºC e UR de 53% ± 1%.
As análises realizadas no dia da colheita (dia 0) e a cada dia do armazenamento
foram: perda de massa, firmeza, compostos fenólicos, espectrometria de
absorção na região do infravermelho, extração de pectinas por três métodos
distintos e análises enzimáticas da β-D-glicosidase e esterase. Os resultados
mostraram que a firmeza dos frutos diminuiu bruscamente nos quatro primeiros
dias de amadurecimento, coincidindo com o aumento da atividade da β-Dglicosidase nesse mesmo período. Foram identificados três compostos fenólicos
por HPLC e a presença de outros picos não identificados, sendo que dois desses
despertaram à atenção, pois tiveram seus teores aumentados durante os dias de
amadurecimento. Os teores de pectina pelo método de extração utilizando as
enzimas celulase e hemicelulase foram maiores (6,7%) que os teores de pectina
citados na literatura (2,5%), o que pode explicar melhor o papel da pectina na
firmeza do fruto. A atividade das esterases foi maior nas membranas celulares da
polpa (57%) em relação à enzima solúvel (8,61%), indicando que essas esterases
de parede são responsáveis, juntamente com a β-D-glicosidase, pela liberação
dos polímeros de pectina.
Guava is considered a quite attractive fruit, due to its color and pleasant aroma, besides being one of the most complete and balanced fruits in terms of its nutritional value, containing high vitamin C levels, reasonable amounts of vitamins A and B and mineral salts such as calcium, phosphorus and iron. Due to its intense metabolism during ripening, guava is a highly perishable fruit, with a very short shelf life, that can reach from three to five days under room temperature. The firmness of green and ripe fruits is mainly related to pectin polymers. The loss of firmness during guava ripening is due to the activity of hydrolytic enzymes, which causes an intense solubilization of cell wall pectins. Given the above, with the objective to try to explain the rapid decrease in firmness, the cell wall composition of guava was investigated, as well as interconnectors between its chains and bound phenolic compounds and enzymatic processes involved in the release and transport of pectin polymers into the cell. Guavas were picked at the “semi-mature” stage and stored for eight days at a temperature of 27º ± 1ºC and RH of 53% ± 1%. The analyses conducted on the harvest day (0) and on each day of storage were: weight loss, firmness, phenolic compounds, absorption spectrometry in the infrared region, pectin extraction by three different methods and enzymatic analyses of β-D glycosidase and esterase. The results show that the firmness of the fruit decreased sharply on the first four days of ripening, coinciding with the increase in the activity of β-D-glucosidase in the same period. Three phenolic compounds were identified by HPLC, and the presence of other unidentified peaks, two of which aroused the attention, since their levels increased during the days of ripening. The contents of pectin by the extraction method using cellulase and hemicellulase were higher (6.7%) than the pectin content in the cited literature (2.5%), which may further explain the role of pectin in fruit firmness. The activity of esterase was greater in the cell membranes of the pulp (57%) compared to the soluble enzyme (8.61%), indicating that these wall esterases are responsible, together with β-D-glucosidase, for the release of the polymer pectin.
Guava is considered a quite attractive fruit, due to its color and pleasant aroma, besides being one of the most complete and balanced fruits in terms of its nutritional value, containing high vitamin C levels, reasonable amounts of vitamins A and B and mineral salts such as calcium, phosphorus and iron. Due to its intense metabolism during ripening, guava is a highly perishable fruit, with a very short shelf life, that can reach from three to five days under room temperature. The firmness of green and ripe fruits is mainly related to pectin polymers. The loss of firmness during guava ripening is due to the activity of hydrolytic enzymes, which causes an intense solubilization of cell wall pectins. Given the above, with the objective to try to explain the rapid decrease in firmness, the cell wall composition of guava was investigated, as well as interconnectors between its chains and bound phenolic compounds and enzymatic processes involved in the release and transport of pectin polymers into the cell. Guavas were picked at the “semi-mature” stage and stored for eight days at a temperature of 27º ± 1ºC and RH of 53% ± 1%. The analyses conducted on the harvest day (0) and on each day of storage were: weight loss, firmness, phenolic compounds, absorption spectrometry in the infrared region, pectin extraction by three different methods and enzymatic analyses of β-D glycosidase and esterase. The results show that the firmness of the fruit decreased sharply on the first four days of ripening, coinciding with the increase in the activity of β-D-glucosidase in the same period. Three phenolic compounds were identified by HPLC, and the presence of other unidentified peaks, two of which aroused the attention, since their levels increased during the days of ripening. The contents of pectin by the extraction method using cellulase and hemicellulase were higher (6.7%) than the pectin content in the cited literature (2.5%), which may further explain the role of pectin in fruit firmness. The activity of esterase was greater in the cell membranes of the pulp (57%) compared to the soluble enzyme (8.61%), indicating that these wall esterases are responsible, together with β-D-glucosidase, for the release of the polymer pectin.
Abstract
Guava is considered a quite attractive fruit, due to its color and pleasant aroma, besides being one of the most complete and balanced fruits in terms of its nutritional value, containing high vitamin C levels, reasonable amounts of vitamins A and B and mineral salts such as calcium, phosphorus and iron. Due to its intense metabolism during ripening, guava is a highly perishable fruit, with a very short shelf life, that can reach from three to five days under room temperature. The firmness of green and ripe fruits is mainly related to pectin polymers. The loss of firmness during guava ripening is due to the activity of hydrolytic enzymes, which causes an intense solubilization of cell wall pectins. Given the above, with the objective to try to explain the rapid decrease in firmness, the cell wall composition of guava was investigated, as well as interconnectors between its chains and bound phenolic compounds and enzymatic processes involved in the release and transport of pectin polymers into the cell. Guavas were picked at the “semi-mature” stage and stored for eight days at a temperature of 27º ± 1ºC and RH of 53% ± 1%. The analyses conducted on the harvest day (0) and on each day of storage were: weight loss, firmness, phenolic compounds, absorption spectrometry in the infrared region, pectin extraction by three different methods and enzymatic analyses of β-D glycosidase and esterase. The results show that the firmness of the fruit decreased sharply on the first four days of ripening, coinciding with the increase in the activity of β-D-glucosidase in the same period. Three phenolic compounds were identified by HPLC, and the presence of other unidentified peaks, two of which aroused the attention, since their levels increased during the days of ripening. The contents of pectin by the extraction method using cellulase and hemicellulase were higher (6.7%) than the pectin content in the cited literature (2.5%), which may further explain the role of pectin in fruit firmness. The activity of esterase was greater in the cell membranes of the pulp (57%) compared to the soluble enzyme (8.61%), indicating that these wall esterases are responsible, together with β-D-glucosidase, for the release of the polymer pectin.
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Agroquímica e Agrobioquímica
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BRAGA, M. A. Parede Celular: análises do mecanismo de perda de firmeza de goiabas cv. Pedro Sato durante o amadurecimento em temperatura ambiente. 2015. 94 p. Dissertação (Mestrado em Agroquímica) - Universidade Federal de Lavras, Lavras, 2015.