Sugar content and dry matter are key factors predicting sprouting of yellow bulb onions regardless of treatment with maleic hydrazide

Abstract

Onions are produced and consumed in large amounts all over the world. Even though the dry onion bulb is well suited to storage, significant losses occur due to sprouting and diseases during the storage period. The objective of this study was to find methods to support decision-making in storage and prevent some of these losses. Three onion cultivars were tested during two storage seasons, and quality indicators such as firmness, sugar content, dry matter content and mineral content were measured. All but one of the samples were treated with maleic hydrazide for sprouting inhibition. Contents of fructose and glucose were found to be connected to the extent of sprouting, with the highest contents coinciding with the onset of sprouting in spring. Firmness and dry matter losses differed between samples from different growing conditions with firmness losses up to 35.2% and dry matter losses between 4.9% and 11.1% found. Dry matter content was significantly connected to the fraction of sprouted bulbs in a sample. While firmness had a decreasing trend for all but one sample, the firmness measurements carried out with a handheld penetrometer were not consistent enough to be a reliable indicator of sprouting.

Keywords

• Dormancy
• postharvest quality
• sprouting
• sugar
• waste reduction