Preharvest Application of Phenylalanine Induces Red Color in Mango and Apple Fruit's Skin.

Michal Fanyuk,Michal Oren-Shamir,Noam Alkan,Rinat Ovadia,Dalia Maurer,Oleg Feygenberg,Manish Kumar Patel

doi:10.3390/antiox11030491

Michal Fanyuk, Michal Oren-Shamir + Show 5 more

Open Access

https://doi.org/10.3390/antiox11030491

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Abstract

Anthocyanins are secondary metabolites responsible for the red coloration of mango and apple. The red color of the peel is essential for the fruit’s marketability. Anthocyanins and flavonols are synthesized via the flavonoid pathway initiated from phenylalanine (Phe). Anthocyanins and flavonols have antioxidant, antifungal, and health-promoting properties. To determine if the external treatment of apple and mango trees with Phe can induce the red color of the fruit peel, the orchards were sprayed 1 to 4 weeks before the harvest of mango (cv. Kent, Shelly, and Tommy Atkins) and apple fruit (cv. Cripps pink, Gala and Starking Delicious). Preharvest Phe treatment increased the red coloring intensity and red surface area of both mango and apple fruit that was exposed to sunlight at the orchard. The best application of Phe was 2–4 weeks preharvest at a concentration of 0.12%, while a higher concentration did not have an additive effect. A combination of Phe and the positive control of prohydrojasmon (PDJ) or several applications of Phe did not have a significant added value on the increase in red color. Phe treatment increased total flavonoid, anthocyanin contents, and antioxidant activity in treated fruit compared to control fruits. High Performance Liquid Chromatography analysis of the peel of Phe treated ‘Cripps pink’ apples showed an increase in total flavonols and anthocyanins with no effect on the compound composition. HPLC analysis of ‘Kent’ mango fruit peel showed that Phe treatment had almost no effect on total flavonols content while significantly increasing the level of anthocyanins was observed. Thus preharvest application of Phe combined with sunlight exposure offers an eco–friendly, alternative treatment to improve one of the most essential quality traits—fruit color.

Highlights

Fruits and vegetables are lost or get a lower price due to poor appearance, quality problems, and consumer preferences [1]
Fruit treated with either Phe or PDJ at harvest and after shelf-life storage had a significantly higher red color intensity of the peel in mango and apple fruit compared to the control (Figures 1A, 2A, S1A and S2A)
Hue values at the reddest point on the fruit peel were evaluated at several time points for mango

Summary

Introduction

Fruits and vegetables are lost or get a lower price due to poor appearance, quality problems, and consumer preferences [1]. Fruit is downgraded if it does not meet a very high standard of quality requirements, causing loss of profitability [2] and possibly food loss. Nutritional value, texture, and aroma are the main factors determining fruit and vegetable quality [3]. Fruit quality and maturity stage can often be indicated by the color of its skin [4]. The red color in fruit peel is a major contributor to the acceptance of fruit, which allows it to be priced higher and sold more [5]. Red color of fruit peel is important in terms of appearance and constitutes an advantage in resistance to pathogens and cold. Mango fruit exposed to Antioxidants 2022, 11, 491.

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