Development of coatings containing mycosporin-like amino acid (MAA) for the control of sunscald in orange fruit (Citrus sinensis L.)

Author(s)

Vanessa Maria Dantas Pedrosa

• Document type: Master's Dissertation
• Press: Jaboticabal. 2021-04-14.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2021-02-24
• Advisor: Gustavo Henrique de Almeida Teixeira; Priscila Lupino Gratão

Abstract

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. (AU)

• FAPESP's process: 19/15083-5 - Development of coatings containing mycosporine like aminoacids (MAA) for controlling sunscald in mango (Mangifera indica L.) and avocado (Persea americana Mill.) fruit
• Grantee: Vanessa Maria Dantas Pedrosa
• Support Opportunities: Scholarships in Brazil - Master