Postharvest Dehydration Temperature Modulates the Transcriptomic Programme and Flavonoid Profile of Grape Berries.

Jiahua Sun,Wanping Li,Li Chen,Kekun Zhang,Ziyu Li,Keqin Chen,Junxia Zhang,Yulin Fang,Zhihao Li

doi:10.3390/foods10030687

Abstract

Raisins are a popular and nutritious snack that is produced through the dehydration of postharvest grape berries under high temperature (HT). However, the response of the endogenous metabolism of white grape varieties to postharvest dehydration under different temperature have not been fully elucidated to date. In this study, the white grape cultivar ‘Xiangfei’ was chosen to investigate the effect of dehydration at 50 °C, 40 °C, and 30 °C on the transcriptomic programme and metabolite profiles of grape berries. Postharvest dehydration promoted the accumulation of soluble sugar components and organic acids in berries. The content of gallic acid and its derivatives increased during the dehydration process and the temperature of 40 °C was the optimal for flavonoids and proanthocyanidins accumulation. High-temperature dehydration stress might promote the accumulation of gallic acid by increasing the expression levels of their biosynthesis related genes and regulating the production of NADP+ and NADPH. Compared with that at 30 °C, dehydration at 40 °C accelerated the transcription programme of 7654 genes and induced the continuous upregulation of genes related to the heat stress response and redox homeostasis in each stage. The results of this study indicate that an appropriate dehydration temperature should be selected and applied when producing polyphenols-rich raisins.

Highlights

Grapes are among the most popular fruits in the world and can be consumed directly and be utilized to produce wine and raisins
The sugar and acid contents did not increase in proportion to the decrease in grape weight, indicating that some sugar and acid components were transformed during the process of dehydration
Based on the analysis described above, the elevated expression of VvSDH3 and VvSDH4 and the accumulation of NADP+ may promote the accumulation of gallic acid (GA) in raisins, and 40 ◦ C was determined to be more conducive to the biosynthesis of GA

Summary

Introduction

Grapes are among the most popular fruits in the world and can be consumed directly and be utilized to produce wine and raisins. With the advantages of having abundant polyphenols, a strong antioxidant capacity, a low to medium glycemic index, and a long shelf life, raisins have become a popular and healthy snack for consumers [1,2]. Due to the limited shelf life of table grapes, the production of raisins is an important means of increasing the economic benefits of vineyards and avoiding waste. The natural dehydration method uses natural heat and air flow to promote grape dehydration, including air drying (PAD) and sun drying (PSD) [5], while the artificial dehydration method includes external auxiliary heating and forced air flow [6]. Some grapes are dehydrated before vinification for sweet sherry wines [7]

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Discussion

Conclusion