A complex interaction between pre-harvest and post-harvest factors determines fresh-cut melon quality and aroma

Natasha D Spadafora,Carsten T Müller,Giacomo Cocetta,Antonio Ferrante,Hilary J Rogers,Roberta Bulgari,Rakhee Dhorajiwala,Anna Spinardi,Marina Cavaiuolo

doi:10.1038/s41598-019-39196-0

Abstract

Melons are prized for their characteristic aroma, however, pre-harvest growth, stage of ripening at harvest, post-harvest processing and storage conditions lead to quality changes in fresh-cut fruit. We considered changes in metabolites and gene expression over 14 days storage to assess underlying mechanisms and identify potential quality markers. Overall, 99 volatile organic compounds (VOCs) were detected and VOC profiles discriminated between two melon seasons, cut-size, storage temperatures and storage time, although season affected their discriminatory power. Abundance of two VOCs fell rapidly and was not associated with cut size, indicating their use as markers for early changes post-processing. Non-acetate to acetate ester ratio differed between the seasons and correlated with changes in alcohol acyl-transferase (CmAAT1) gene expression. Furthermore, CmAAT1 expression clustered with two ester VOCs that may be potential new products of this enzyme. Season also strongly affected post-harvest sugar content, most likely attributable to meteorological differences during growth. Storage temperature and cut size affected expression of transcription factors ERF71, ERF106, and TINY, whose expression generally rose during storage, probably related to increased stress. Thus, although time × temperature of storage are key factors, pre-harvest conditions and fruit processing impact significantly gene expression and aroma loss post-harvest.

Highlights

Commercialization and consumption of ready to eat cut melons is an increasing market[1]
Fruit deterioration leads to increased reactive oxygen species (ROS) and consequent loss of membrane integrity, which can be assessed by measurement of lipid peroxidation[12]
A key gene linked to volatile organic compounds (VOCs) production in melon fruit is alcohol acyl-transferase (CmAAT1) that catalyses the formation of esters from a range of alcohols and acyl-CoA substrates[25] with a preference for the formation of E-2-hexenyl acetate and hexyl hexanoate[26]

Summary

Introduction

Commercialization and consumption of ready to eat cut melons is an increasing market[1]. Preparation for fresh fruit salads involves wounding the fruit flesh, triggering a series of physiological events that can lead to a severe loss of product quality[8]. These physiological processes can be slowed down by lowering the storage temperature[7]. During post-harvest processing and storage of fruit, the majority of the cells are still metabolically active and responses to the stresses imposed are likely to involve changes in gene expression, very few studies are available[24]. Recent metabolomic analyses[27] suggest that this enzyme may be involved in the biosynthesis of several ethyl, thio and thioethyl esters

Methods

Results

Conclusion