The impact of sulphur on breadmaking quality is fairly well known, but what about biscuits?
LACK of sulphur could be restricting the use of flour milled for biscuit making from some UK grown wheat. As reduced levels of air pollution cut the amount of free sulphur deposited on fields, and as supplies of the biscuit makers preferred variety decline, suitable flour is less easy to find.
Biscuit makers avoid flour with poor baking quality and source their needs from mainly Riband. But a trial which started this season could show how to boost quality to improve market acceptance for Riband, and other more modern biscuit types.
Air pollution is reducing the amount of free sulphur fall-out from the atmosphere and as levels decline deficiencies are appearing in crops across the country.
Although so far biscuit wheats have not obviously suffered, their potential could have been compromised as deficiencies become more widespread.
This, and the decline in popuarity of Riband, could be why millers are having increasing difficulty finding supplies of flour suitable for biscuit making.
It is focusing attention on why other alternative varieties are less suitable, and how their biscuit-making qualities could be improved.
A research project now underway at Harper Adams College in Shopshire is geared to assessing the role of sulphur in biscuit flour quality, and finding ways to improve flour acceptability.
Riband is the preferred variety for this added value market. Its flour has good extensibility qualities, and it can be stretched into place without any risk of shrinking during baking. Rich Tea biscuits are particularly prone to this if unsuitable flour is used.
According to NIAB, Riband had a 33% share of wheat seed certified in 1992, but by 1996 this had fallen to 23%. A higher proportion of the national crop will have been Riband because of farm-saved seed.
However, market share is expected to fall further as newer higher yielding types, such as Consort, gain favour with wheat growers across the country.
"In the past vast acreages of Riband were grown and biscuit makers were spoilt for choice, but it is a different story today," comments the Colleges senior agronomy lecturer Peter Kettlewell.
"The screw is tightening as Ribands share of the UK wheat crop declines and supplies of suitable grain dry up. There is an urgent need to discover why some other wheat is less suitable, the finger of suspicion points at lack of available sulphur."
Between 1986 and 1988 he conducted trials to see if lack of it was affecting breadmaking quality. No obvious link was found and loaf volumes were similar when made with flour milled from Avalon, Mercia, and Moulin.
The results were pigeon-holed until last year when they were reviewed. Although lack of sulphur had no effect on loaf volumes, it did seem to affect flour extensibility.
"The evidence screamed at me. But we had focused on breadmaking types so a fresh look was urgently needed at biscuit types," says Mr Kettlwell. "After talking to biscuit makers I realised lack of sulphur could be the missing link that had been restricting the millers supplies of flour from Riband, and other varieties.
In 1970, before the full benefits of the various Clean Air Acts were felt, 6.5m tonnes of S02 were released into the atmosphere over Britain. As the anti-pollution regulations began to bite the amount reduced. By 1986 there was a drop to about 4m tonnes, and to just 3m tonnes by 1995.
With such a rapid decline of atmospheric pollution the level of free sulphur fall-out onto farmland also fell and deficiency symptoms started to appear in crops across the country.
Initially it was the highly susceptible oilseed rape grown in areas away from heavy industry which were affected. Later, trouble was seen in cereals, and in parts of the country previously considered free from sulphur deficiency risks.
As the deficiency grip tightens the grain quality may be ruined, and supplies of suitable home-grown biscuit wheat could dry up.
With no lack of high quality biscuit wheat available in France there is a risk millers may turn to imports from the other side of the English Channel to plug the gap.
Each year around 1m tonnes of UK-sourced wheat is milled for biscuit flour, it is an important outlet which must not be surrendered to imports.
Just as some crops are more susceptible to lack of sulphur than others, so some cereal varieties could be more vulnerable to deficiency.
Bread wheats have a higher natural concentration of the vital element than the feeders, and it may be that biscuit types contain less as well.
In 1992/93 a Rothamsted survey found that Mercia had far more sulphur in its grain than Riband, possibly a reflection of increased protein content.
Harper Adams College in Shropshire recently secured commercial funding for a three-year trial to investigate the effects of sulphur on flour extensibility.
Two varieties, Riband and Consort, are being grown at the college near Newport, and on farms in Devon and Suffolk. The south-west location was chosen as it is even further away from heavy industry than East Anglia, which is particularly deficient in sulphur.
"Our work is at an early stage, but the results from this season should be interesting and show whether we are likely to establish a link between sulphur and the quality of biscuit flours.
"It is possible that lack of it has restricted the potential markets for some Riband wheat grown over the past 10 years. If this has been happening it should be relatively easy to correct so boosting the chances of grain meeting the biscuit makers needs," says Mr Kettlewell.