The UK blackcurrant industry is valued at £10m (c €14.6m), with around 15 thousand tonnes of the fruit harvested each year. GlaxoSmithKline is believed to have contractual arrangements with almost all of the country's 50-odd growers for the production of its popular Ribena drink
If researchers at the Scottish Crop Research Institute and East Malling Research in Kent continue to see success in their endeavour to raise vitamin C levels in the fruit themselves, this could have a knock-on affect for the food industry, enabling higher levels in Ribena and other consumer products from less currants.
Vitamin C plays an important role in tissue growth and repair and boosts the immune system. But since it is water soluble, the body is unable to store it. The UK's Food Standards Agency recommends daily intake of 40mg, but despite campaigns to boost fruit and vegetable consumption it is thought that most people fail to achieve this.
The researchers have reported their progress to date in the July issue of Business, the publication of the Biotechnology and Biological Sciences Research Council (BBSRC).
The key finding so far hinges on the relationship between starch levels in a bush's leaves after the fruit have been harvested and vitamin C levels in the following year's fruit.
Research leader Dr Robert Hancock explained that vitamin C accumulation occurs when the blackcurrants are still green and is fuelled by sugars. Once the fruit take on colour, the vitamin C levels off.
At the time of harvest, the leaves are very photosynthetic and sugars generated by the solar energy hitting the fruit over the winter months are stored as starch. Come spring, these starches are transported to the new fruit to fuel vitamin C synthesis.
Thus, there appears to be a correlation between higher starch levels and higher vitamin C.
"Understanding how and when vitamin C is produced and accumulates in the blackcurrant plants has clear benefits for the consumer," said Dr Hancock. "We can grow crops that produce juice that will have higher levels of vitamin C and a better taste."
As well as adjusting carbohydrate levels across the plant in order to alter starch deposits, practical ways of optimising starch production are currently being devised, including pruning to optimise photosynthesis - a novel approach since blackcurrants have traditionally been a low maintenance crop.
The team is also developing techniques and knowledge to speed up the breeding of super blackcurrant bushes.
Dr Hancock explained that the next stage involves predictive screens that will be able to determine from a biochemical marker in seedlings what the vitamin C content of the fruit is likely to be once the plant reaches maturity.
Since each bush takes three years to produce a full harvest, this will considerably speed up the process as it will allow the researchers to make more crosses each year, between 30 and 50 per cent of which may be discarded at an early stage.
Although it looks promising thus far, it will be some time yet before products containing super blackcurrants actually come to market.
The current research is under a £1.2m (€1.75m) public-private partnership overseen by Defra. The public portion comes from the BBSRC and the Scottish Executive Environment and Rural Affairs Department. The private portion is from GlaxoSmithKline's coffers and the Horticultural Development Council, which is a conduit for contributions by growers themselves.
Since public funds are being used, GSK does not have exclusivity on the resulting fruit from this particular project. Rather, this research is intended to benefit the sector as a whole.
However GSK may well benefit from being close to the research, and from further developing any offshoots. Dr Hancock said that GSK is also the sole funder of some other projects with SCRI, and in these cases does have exclusivity on the findings.
Vitamin C levels are measured using HPLC (high pressure liquid chromatography), and vary between a cultivar called Hedda, not used by GSK, which has 60mg of vitamin C per 100ml of juice and others such as Baldwin, which have between 150 and 160mg/100ml.
Dr Hancock said that SCRI has managed to attain levels of vitamin C of 400 to 450mg/100ml in some of its experimental varieties, but these may be lacking in other desirable areas, such as colour, taste or disease resistance.
The SCRI says that varieties it has bred - all of which are named after Scottish mountains - are used in 50 per cent of the global crop, and new varieties are introduced each year.
Other key growing regions include Eastern Europe and Scandinavia, and New Zealand.
This years New Zealand harvest was around 8000 tonnes, 90 per cent of which was for export to Europe.
New Zealand's HortResearch is another key player in blackcurrant breeding, and has also been looking at vitamin C levels, which have a knock on effect on levels of beneficial anthocyanins antioxidants.
Although SCRI and HortResearch are not presently working together over vitamin C, they have collaborated closely in the past. In May it drafted in some New Zealand varieties in a bid to prevent the UK's yield being impacted by the warmer winters experienced in recent years.