The Investigation of Phenylalanine, Glucosinolate, Benzylisothiocyanate (BITC) and Cyanogenic Glucoside of Papaya Fruits (Carica papaya L. cv. ‘Tainung No. 2’) under Different Development Stages between Seasons and Their Correlation with Bitter Taste

Irvan Prawira Julius Jioe,Ching-Chang Shiesh,Huey-Ling Lin

doi:10.3390/horticulturae8030198

Irvan Prawira Julius Jioe, Ching-Chang Shiesh + Show 1 more

Open Access

https://doi.org/10.3390/horticulturae8030198

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Abstract

Papaya fruit is one of economic crops in Taiwan, mostly eaten as table fruits. In some Asian countries, unripe papaya fruit is eaten as salad and this led to trends in Taiwan as well. However, unripe papaya fruit may taste bitter during cool seasons. Glucosinolate and cyanogenic glucoside are among the substances that cause bitter taste in many plants, which can also be found in papaya. However, there is still no report about the relationship between seasons and bitter taste in papaya fruits. Thus, the purpose of this study is to investigate the glucosinolate biosynthesis and its correlation between bitterness intensity during cool and warm seasons. The bitterness intensity was highest at the young fruit stage and decreased as it developed. In addition, the bitterness intensity in cool season fruits is higher than in warm season fruits. Cyanogenic glucoside and BITC content showed negative correlation with bitterness intensity (r = −0.54 ***; −0.46 ***). Phenylalanine showed positive correlation with bitterness intensity (r = 0.35 ***), but its content did not reach the bitterness threshold concentration, which suggested that phenylalanine only acts as cyanogenic glucoside and glucosinolate precusors. Glucosinolate content showed positive correlation with bitterness intensity at different developmental stages (r = 0.805 ***). However, the correlation value in different lines/cultivars decreased (0.44 ***), suggesting that glucosinolate was not the only substance that caused bitter taste in immature papaya fruits.

Highlights

IntroductionPapaya is a short growing tropical fruit that can be harvested continuously at 8–9 months after sowing seeds [1,2]
Publisher’s Note: MDPI stays neutralPapaya is a short growing tropical fruit that can be harvested continuously at 8–9 months after sowing seeds [1,2]
StageIntensity during Warm and Cool during Warm and Cool Seasons In Figure 1 the results showed that the warm season had less 7 node fruits tha In Figurecool

Summary

Introduction

Papaya is a short growing tropical fruit that can be harvested continuously at 8–9 months after sowing seeds [1,2]. Papaya is usually eaten as table fruits. In some Asian countries, unripe papaya can be consumed [4,5], usually as a salad or cooked dish [6]. Unripe papaya cuisine has begun to become popular in Taiwan, but it can taste bitter randomly during the cool season. Field inspection was needed for further understanding. It was found that the growers usually harvest the fruits when the pulp is still white in color. The bitter taste is thought to have a close relationship with the fruit development

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