Rind Color Development in Satsuma Mandarin Fruits Treated by Low-intensity Red Light-emitting Diode (LED) Irradiation

Abstract

Here, we investigated the effect of irradiation by a low-intensity red light-emitting diode (LED) (photon flux μmol•m_ 2 •s _ 1 ) on rind color development in Satsuma mandarins after harvesting at two different periods. In the early harvest fruit, the a* value for Satsuma mandarin peel treated by red LED irradiation was 2.7 and 2.4 times higher than that for the dark treatment fruit at 4 and 8 days irradiation, respectively. In the commercial harvest fruit, the a* value of the peel treated by red LED irradiation was 1.2 and 1.4 times higher than for dark treatment at 4 and 8 days irradiation, respectively. Additionally, we examined the influence of red LED irradiation on the internal fruit quality of Satsuma mandarins from the two harvest periods. Low-intensity red LED irradiation did not affect fruit quality. We elucidated the effect of intermittent red LED irradiation on the change in a* value of mandarin fruits. These results indicated that treatment with low-intensity red LED irradiation is sufficient to develop a degree of rind color in mandarins without affecting the internal fruit quality.Keywords: citrus, fruit quality, postharvest, rind color, red light, storage IntroductionThe peel color of Satsuma mandarin fruits is an important factor in customer satisfaction. In recent years, fruits with a low level of coloration despite the degree of flesh maturation have been shipped; this type of fruit development occurred because high fall temperatures caused the flesh to ripen while some green coloration remained in the peel.Satsuma mandarin production is faced with challenges due to global warming (Sugiura and Yokozawa, 2004;Sugiura et al., 2007). One impact of global warming on fruit cultivation is the occurrence of rind puffing. Therefore, it has become increasingly common for growers to treat fruit with gibberellic acid and prohydrojasmon mixtures (hereafter, GP solutions) three months before harvesting, as a method to reduce rind puffing (Makita and Yamaga, 2006;Nakatani et al., 2014). However, treatment with GP solutions is problematic, as gibberellin delays coloration (Porat et al., 2001), and interested parties are keen to find a method that simultaneously solves issues related to both rind puffing and coloration delay. The ability to improve coloration through some type of fruit processing would increase its marketability. In Japanese citrus fruit production areas, mulching the ground with light-reflective, non-woven fabric sheets during cultivation has been embraced as a means of improving coloration and increasing sugar content (Morinaga et al., 2004;Muramatsu et al., 2005). In addition, in the past there have been many studies on methods of improving fruit coloration during post-harvest storage. High-temperature pretreatment, in which the fruit is maintained at 15 _ 20℃ for a week, has been brought into practical use (Murata and Yamawaki, 1992). However, this treatment involves the extended use of heaters (at least 8 days), and improved technology is being sought to reduce costs. In addition, severa...

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“…Light is important to the development of the photosynthetic apparatus and is involved in both degreening and regreening in the peel of citrus fruit. Yamaga et al (2016) reported that low-red LEDs increased the a* value of peel in early-harvest satsuma mandarin fruit. In red grapefruit, high intensity light inhibited chlorophyll breakdown and carotenoid accumulation in the peel of fruit located on the branch (Lado et al, 2015).…”

“…In satsuma mandarins, Izumi et al (1992) reported that high-intensity sunlight promoted the coloration of fruit. Yamaga et al (2016) indicated that exposure to low-intensity red light-emitting diode (LED) irradiation led to development of a degree of This article is an Advance Online Publication of the authors' corrected proof. Note that minor changes may be made before final version publication.…”

Modification of the Light Environment Influences the Production of Horticultural Crops

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