How to manage onion taste and pungency

Taste and pungency are key quality characteristics of the onion crop. Pungency is largely due to the level of sulphur - based non-protein amino acids they contain. Sweetness can be assessed by the levels of sugars in the bulb. They vary among types and cultivars however it is well known that good nutrition is essential to manage these characteristics.

Sulphur is critical to onion pungency

Sulphur is critical to the taste and pungency of the bulb. Supplies need to be tailored to suit the desired market requirement. Sulphur can also improve skin strength and colour, and has a marked effect on the pungency of the onion through increasing the pyruvic acid content of the bulb. Therefore, it is important to use the right soil and an appropriate rate and timing of sulphur that satisfies market demands.

Effect of sulphur on onion pungency

Sulphur reduces onion sugar content

Sulphur also has a marked effect on bulb sugar content, so soil type and use of sulphur as part of a nutritional program have to be carefully considered in order to meet market requirements. For example, sweet onions benefit from being grown in low sulphur soils and should have low S-nutrition regimes with most of the S applied early season to minimise uptake into the onion bulb.

Effect of sulphur on onion pungency and sugar content