Desenvolvimento de recobrimentos contendo micosporina tipo aminoácido (MAA) para o controle de escaldadura em frutos de laranjeira (Citrus sinensis L.)
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Data
2021-02-24
Autores
Pedrosa, Vanessa Maria Dantas
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Universidade Estadual Paulista (Unesp)
Resumo
A laranja é um fruto amplamente produzido no Brasil e este é bastante sensível à ocorrência de distúrbios fisiológicos, como a escaldadura causada pela exposição à radiação solar, sendo um problema que afeta sua qualidade. Tradicionalmente a ocorrência desta injúria é contornada com a pulverização dos frutos com hidróxido de cálcio, contudo esta prática nem sempre é eficiente. Sabendo-se da eficiência das micosporinas tipo aminoácido (MAA) como proteção contra as radiações ultravioleta (UV) em diversos organismos aquáticos e de sua adição em protetores solares destinados à seres humanos e não havendo aplicações visando ao controle da escaldadura de frutos, este trabalho teve por objetivo desenvolver e caracterizar emulsões de base lipídica adicionada de MAA para uso na pré-colheita dos frutos de laranjeira. Para o desenvolvimento e caracterização das emulsões foram utilizadas as bases lipídicas (BL) óleo de milho (OM) e de soja (OS) e as ceras de carnaúba (CC) e de abelha (CA) a 10% (m/v) A partir dos resultados de coloração, pH, condutividade, viscosidade, teor de matéria-seca (MS), solubilidade em água, bem como da estabilidade das emulsões nos testes de centrifugação, estresse térmico e ciclos de congelamento e descongelamento, foi escolhida a emulsão contendo CC e hidróxido de amônio para a adição de MAA. Para isso foi utilizado o produto comercial Helioguard™ 365 como fonte de MAA e este foi adicionado nas concentrações de 0%, 1%, 2% e 4% (v/v) à emulsão de base lipídica. A incorporação de MAA não afetou as características tecnológicas da emulsão, como também a estabilidade da mesma. Destaca-se que com a adição de MAA foram observados aumentos na absorbância na região do UV-B (280 a 300 nm), o que possibilita o uso desta emulsão como barreira química para o controle da escaldadura. Visando confirmar a eficiência dessa emulsão em condições de campo, emulsões contendo 0%, 1%, 2% e 4% (v/v) de Helioguard™ 365 foram aplicadas na pré-colheita de frutos de laranjeiras das cultivares ‘Hamlin’, ‘Pera-rio’ e ‘Valência’, em intervalos de 21 dias a partir da primeira aplicação. Foi utilizado como controle positivo a aplicação de hidróxido de cálcio a 5% e o como controle negativo os frutos não tratados. Apesar das emulsões terem apresentado aumentos de absorbância no UVB, a adição de MAA não resultou no controle da escaldadura. Da mesma forma, não foram observadas diferenças significativas para a maioria dos parâmetros físico-químicos analisados, bem como para os parâmetros referentes ao metabolismo oxidativo, com exceção da coloração e dos teores de sólidos solúveis e ácido ascórbico para as três cultivares. Desta forma, o uso de MAA nas concentrações testadas foram pouco eficientes no controle de escaldadura em frutos de laranjeira.
Orange is a fruit widely produced in Brazil and it is very sensitive to the occurrence of physiological disorders, such as sunscald caused by the exposure to solar radiation, being a problem that affects the quality of this fruit. Traditionally, the occurrence of this injury is controlled by spraying the fruits with calcium hydroxide, however this practice is not always efficient. Knowing the efficiency of the mycosporine-like amino acids (MAA) as a protection against ultraviolet (UV) radiation in several aquatic organisms and their incorporation into sunscreens intended for humans, and as there are no applications aimed at controlling fruit sunscald, the objective of this study was to develop and characterize lipid-based emulsions containing MAA for use in the pre-harvest of orange fruits. For the development and characterization of the emulsions, lipid bases (BL), corn oil (OM) and soybean oil (OS) and carnauba wax (CC) and beeswax (CA) were used at 10% (w/v). From the results of color, pH, conductivity, viscosity, dry matter (DM) content, water solubility, as well as the stability of the emulsions in the centrifugation tests, thermal stress and freezing and thawing cycles, the emulsion containing CC and ammonium hydroxide was elected for the addition of MAA. For this, the commercial product Helioguard ™ 365 was used as a source of MAA and this was added in concentrations of 0%, 1%, 2% and 4% (v/v) to the base emulsion. The incorporation of MAA did not affect the technological characteristics of the emulsion, as well as its stability. It is noteworthy that with the addition of MAA, increased the absorbance in the UV-B region (280 to 300 nm), which makes it possible to use this emulsion as a chemical barrier to control sunscald. In order to confirm the efficiency of this emulsion under field conditions, emulsions containing 0%, 1%, 2% and 4% (v / v) of Helioguard ™ 365 were applied in the pre-harvest of orange of the cultivars' Hamlin ',' Pera-rio 'and' Valencia ', at intervals of 21 days from the first application. The application of 5% calcium hydroxide was used as a positive control and the untreated fruits as a negative control. Although the emulsions showed increases in UV-B absorbance, the addition of MAA did not result in the sunscald control. Likewise, no significant differences were observed for most of the analyzed physical-chemical parameters, as well as for parameters related to oxidative metabolism, except for the color and content of soluble solids and ascorbic acid for the three cultivars. Thus, the use of MAA in the tested concentrations was not efficient in the control of sunscald in orange fruits.
Orange is a fruit widely produced in Brazil and it is very sensitive to the occurrence of physiological disorders, such as sunscald caused by the exposure to solar radiation, being a problem that affects the quality of this fruit. Traditionally, the occurrence of this injury is controlled by spraying the fruits with calcium hydroxide, however this practice is not always efficient. Knowing the efficiency of the mycosporine-like amino acids (MAA) as a protection against ultraviolet (UV) radiation in several aquatic organisms and their incorporation into sunscreens intended for humans, and as there are no applications aimed at controlling fruit sunscald, the objective of this study was to develop and characterize lipid-based emulsions containing MAA for use in the pre-harvest of orange fruits. For the development and characterization of the emulsions, lipid bases (BL), corn oil (OM) and soybean oil (OS) and carnauba wax (CC) and beeswax (CA) were used at 10% (w/v). From the results of color, pH, conductivity, viscosity, dry matter (DM) content, water solubility, as well as the stability of the emulsions in the centrifugation tests, thermal stress and freezing and thawing cycles, the emulsion containing CC and ammonium hydroxide was elected for the addition of MAA. For this, the commercial product Helioguard ™ 365 was used as a source of MAA and this was added in concentrations of 0%, 1%, 2% and 4% (v/v) to the base emulsion. The incorporation of MAA did not affect the technological characteristics of the emulsion, as well as its stability. It is noteworthy that with the addition of MAA, increased the absorbance in the UV-B region (280 to 300 nm), which makes it possible to use this emulsion as a chemical barrier to control sunscald. In order to confirm the efficiency of this emulsion under field conditions, emulsions containing 0%, 1%, 2% and 4% (v / v) of Helioguard ™ 365 were applied in the pre-harvest of orange of the cultivars' Hamlin ',' Pera-rio 'and' Valencia ', at intervals of 21 days from the first application. The application of 5% calcium hydroxide was used as a positive control and the untreated fruits as a negative control. Although the emulsions showed increases in UV-B absorbance, the addition of MAA did not result in the sunscald control. Likewise, no significant differences were observed for most of the analyzed physical-chemical parameters, as well as for parameters related to oxidative metabolism, except for the color and content of soluble solids and ascorbic acid for the three cultivars. Thus, the use of MAA in the tested concentrations was not efficient in the control of sunscald in orange fruits.
Descrição
Palavras-chave
Caracterização, Emulsão, Estabilidade, Helioguard™ 365, Porphyra umbilicalis, Characterization, Emulsion, Stability