Towards sustainable onion storage : postharvest quality diagnostics using volatile organic compounds and physiological metrics

Abstract

Onion is an important component of the diets of many cultures worldwide, and also one of the most commonly produced vegetables. The onion bulb is a well-adapted storage organ and many of the harvested bulbs are stored for several months to ensure year-round availability to consumers. However, significant amounts are lost due to sprouting, loss of water, loss of dry matter, fungal infections and bacterial infections. To optimise storage and enable sales at the correct point in time to reduce losses decision support systems are needed to identify signs of quality problems. One potential such system is the monitoring of volatile organic compounds in the air of storage facilities to detect developing quality problems, such as storage diseases. In this thesis, the volatile organic compounds emanating into the headspace of onion bulbs affected by Fusarium basal plate rot, Penicillium rot or Pectobacterium-caused soft rot were investigated. The aim was to identify the compounds that are relevant as indicators of developing storage diseases, and which could be the target of future monitoring systems. Several relevant indicator compounds were found. Some of them are naturally occurring onion metabolites whose relative abundance changed, including methyl propyl disulfide and dimethyl disulfide. Others, such as ethenylbenzene and 2,3-butanediol are products typical of fungal or bacterial metabolism. Other systems for storage monitoring may include physiological measurements to predict quality changes such as sprouting. Therefore, the thesis also investigated the connection between selected physiological indicators and sprouting. It was found that the changing concentrations of glucose, fructose and sucrose, and the decreasing dry matter contents of the bulbs had a significant connection to the start of sprouting.

Keywords

Allium cepa; basal plate rot; blue mould; e-nose; food loss; non-structural carbohydrates; SPME-GC-MS; soft rot; sugar; VOC

Published in

Acta Universitatis Agriculturae Sueciae
2025, number: 2025:10
Publisher: Swedish University of Agricultural Sciences

SLU Authors

• Kleman, Isabella

  • Department of Biosystems and Technology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Agricultural Science

Publication identifier

• DOI: https://doi.org/10.54612/a.5qnn6nnov2
• ISBN: 978-91-8046-445-1
• eISBN: 978-91-8046-495-6

Permanent link to this page (URI)

https://res.slu.se/id/publ/132950