Articles
EFFECTS OF HIGH TEMPERATURE AND HIGH SOLAR IRRADIANCE ON SUNBURN, QUALITY, AND SKIN PIGMENTS OF APPLE FRUIT
Article number
903_144
Pages
1025 – 1039
Language
English
Abstract
High solar irradiance and/or heat stress cause several skin disorders (e.g. sunburn, Fuji stain, lenticel marking, and Granny Smith sunburn scald) in apple (Malus × domestica Borkh.), but sunburn usually results in the most cullage.
Three types of sunburn in apple have been identified and the specific causes of each have been determined.
The first type, sunburn necrosis, appears after high fruit surface temperature (FST) (~52°C) causes thermal cell death.
The second type, sunburn browning, is caused by concomitant exposure to high FST (46 to 49°C depending on cultivar) and UV-B radiation, but does not result in cell death.
The third type, photooxidative sunburn, requires only visible light and affects shaded (non-acclimated) apples that are suddenly exposed to solar radiation.
Because sunburn browning is most prevalent commercially and is often the major cause of cullage of apples, we examined the effects of sunburn browning on internal fruit quality and pigment concentrations.
Apples were sorted into five grades: Sb-0, no sunburn; Sb-1 to Sb-4, increasing severity of sunburn browning.
As severity of sunburn browning increased in Gala, flesh firmness and soluble solids concentration (SSC) increased, but titratable acidity (TA) decreased.
During 6 months of cold storage, firmness and TA decreased, but SSC was relatively stable.
The ratio of SSC to TA increased dramatically during 6 months in cold storage; ratio increases were most dramatic in fruit with more severe sunburn browning because TA declined so markedly.
Sunburn browning also caused significant changes in pigment concentrations.
In Fuji concentrations of chlorophyll a, chlorophyll b, and anthocyanin (idaein) were lower in sunburned peel.
Concentrations of chlorogenic acid, β-carotene, xanthophyll pigments and major quercetin glycosides were higher in sunburned peels than in non-sunburned peels.
RAYNOX®, a sunburn protectant invented during the course of these studies, reduced sunburn browning by about 50%, on average.
Three types of sunburn in apple have been identified and the specific causes of each have been determined.
The first type, sunburn necrosis, appears after high fruit surface temperature (FST) (~52°C) causes thermal cell death.
The second type, sunburn browning, is caused by concomitant exposure to high FST (46 to 49°C depending on cultivar) and UV-B radiation, but does not result in cell death.
The third type, photooxidative sunburn, requires only visible light and affects shaded (non-acclimated) apples that are suddenly exposed to solar radiation.
Because sunburn browning is most prevalent commercially and is often the major cause of cullage of apples, we examined the effects of sunburn browning on internal fruit quality and pigment concentrations.
Apples were sorted into five grades: Sb-0, no sunburn; Sb-1 to Sb-4, increasing severity of sunburn browning.
As severity of sunburn browning increased in Gala, flesh firmness and soluble solids concentration (SSC) increased, but titratable acidity (TA) decreased.
During 6 months of cold storage, firmness and TA decreased, but SSC was relatively stable.
The ratio of SSC to TA increased dramatically during 6 months in cold storage; ratio increases were most dramatic in fruit with more severe sunburn browning because TA declined so markedly.
Sunburn browning also caused significant changes in pigment concentrations.
In Fuji concentrations of chlorophyll a, chlorophyll b, and anthocyanin (idaein) were lower in sunburned peel.
Concentrations of chlorogenic acid, β-carotene, xanthophyll pigments and major quercetin glycosides were higher in sunburned peels than in non-sunburned peels.
RAYNOX®, a sunburn protectant invented during the course of these studies, reduced sunburn browning by about 50%, on average.
Publication
Authors
L.E. Schrader, C.B. Kahn, D.A. Felicetti, J. Sun, J. Xu, J. Zhang
Keywords
Malus × domestica, flesh firmness, soluble solids concentration, titratable acidity, anthocyanins, chlorophylls, carotenoids, flavonols, quercetin glycosides, RAYNOX®
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