The Supasweet onion 







Onions grown in the UK are traditionally strong and pungent, great for cooking in winter stews but not so suitable for eating fresh in salads or on hamburgers.  Milder flavoured onions are grown in other countries, and imported into the UK.  About 100,000 tonnes of onions were imported and sold as 'mild' in the UK in 2000, since until recently no mild-flavoured varieties were suitable for growing in the UK climate.  In addition, everyday experience suggested that the flavour of 'mild' onions was quite variable, with some being quite strong. Mild and sweet onions have captured about 25% of the US onion market and demand in the UK is increasing.

Collaborative work between ourselves, HRI Wellesbourne and UK onion growers, importers and retailers, with financial support from DEFRA has evaluated the flavour of onions on sale in the UK, and searched for a milder sweeter variety that could be produced in the UK.  Part of the project assessed the flavour of onions, using both human perceptions and chemical methods, so that we would have an objective way of providing quality control. After the first trial marketing in 2002, the new sweet onions were sold in selected supermarkets nationwide in 2003.

These onions were initially only available for a short season (July - September) so re-introduced the idea of seasonal produce. However, from 2006 the onion growers and importers were able to source sweet onions from other parts of the world to extend the season, and are now committed to supplying sweet onions to UK consumers all year round. For example, selected branches of J. Sainsbury and Booths now sell sweet onions all year. The sweet onion even has its own website at and featured in the BBC programme 'Ever wondered about food?' in 2007.

DEFRA produced a brochure about this project in 2003: LINK collaborative research case study: ONIONS WITHOUT TEARS Classification of flavour strength opens up a new market for mild onions to UK producers.

Better understanding of the basic biology and science of the flavour compounds in onions and how to measure them was developed at Liverpool from the early 1990s with financial support from the UK government. This was essential before the Supersweet onion could be developed. It is described on page 12 in this booklet: 'Bioscience and Innovation' October 2004, Biotechnology and Biological Sciences Research Council

We have published a scientific paper about the Supersweet project: T. Crowther, H. A.  Collin, B. Smith, A. B. Tomsett, D. O’Connor and M. G. Jones (2005) Assessment of the flavour of fresh uncooked onions by taste-panels and analysis of flavour precursors, pyruvate and sugars. Journal of the Science of Food and Agriculture, 85 112 - 120

Supasweets packaged for J Sainsbury (top image)
and Tesco (lower image)
A group of Supasweet onions,
a truly mild, sweet onion from the UK

The Supasweet onion in the news

In June 2005 the Supasweet onions again attracted media attention:

By late-July 2003, only 2 weeks after the the season's launch, several tons of the onions had been sold. The media said .....

When they were first sold in July/August 2002 the Supasweet onions also attracted interest from the media ...

For further information about the Supasweet onion:

Allium and Brassica Centre, Wash Road, Kirton, Boston, Lincs., PE20 1QQ, U.K.

Tel: +44 (0) 1205 723414 Fax: +44 (0) 1205 722995 email: