The role of lipids in determining gas bubble retention and stability in wheat dough

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The proposal will exploit new analytical opportunities and approaches to clearly define the role of endogenous wheat lipids in determining gas bubble stability in dough and hence bread making quality, and exploit this knowledge by selecting improved wheat lines for breeding.
It will benefit from a unique combination of skills and facilities, including new analytical capabilities offered by the "lipidomics platform" at Rothamsted Research and biophysical methodologies including atomic force microscopy (AFM) at IFR. Baking and analysis of bread structure will be carried out at Campden BRI.
1. Fermented dough from a single variety of UK breadmaking wheat will be fractionated to isolate lipids associated with the gas bubble interface and profiled by electrospray tandem mass spectrometry (ESI-MS/MS). Surface tension and surface dilatational rheology will identify functional behaviour of individual lipids.
2. Mechanisms of gas bubble stabilisation by the lipids will be determined by foam microconductivity, interfacial tension, interfacial rheology and interfacial imaging using AFM.
3. The functional behaviour of individual lipids will be established by addition to dough systems. Proving volumes and the evolution and properties of gas cells will be determined by microscopy and image analysis of dough proofed against a glass plate. Gold-labelled lipids will be incorporated and their location established by SEM.
4. Full scale baking trials will determine the impact of lipid composition on bread making quality, and innovative image analysis techniques will quantify the impact on crumb structure of the final product.
5. Genetic variation in lipid composition and gas bubble stability will be determined by analysis of 20 modern wheat line
This knowledge will lead to the production of UK grown wheat lines with improved bread making capacities and facilitate the production of healthier breads with reduced levels of salt and fat.

About 6 million tonnes of wheat are milled in the UK, with most of the flour being used for breadmaking. Most of this is "home grown" but it is also necessary to import significant quantities of grain from the EU and third countries to maintain the quality of bread demanded by consumers. The volume of imported wheat ranges up to about 1 million tonnes a year depending on the quality of the UK harvest. Improved quality for breadmaking therefore remains an important target for UK wheat breeders and farmers.
The demonstration of a clear role of lipids in determining dough stability will therefore provide a new target for UK wheat breeders in addition to the current selection for glutenin alleles associated with dough strength. This will enable breeders to improve wheat quality in a more focussed and rational manner, producing wheat varieties tailored for particular end uses.
Farmers will benefit through a wider choice of wheat varieties, with improved, rationalised end product quality, ensuring premium prices for high quality crops, and be more competitive with the quality of imported grain.
Processors will be less reliant on expensive import costs to maintain flour quality, and will be able to supply manufacturers with a more consistent supply of UK grown wheat.
Improved baking quality will allow manufacturers to develop a wider range of products, including healthier products with reduced levels of salt and fat and reduce the use of synthetic emulsifiers.
Consumers will benefit from good quality, low cost products, due to reduced levels of imports. A wider choice of good quality, healthier products will also improve consumers ability to maintain a healthy lifestyle.
The nation as a whole will ultimately benefit through reduced reliance on imported products, enhanced competitiveness from UK breeders and growers.
Improving the intrinsic quality of UK breadmaking wheats will therefore accrue benefits throughout the food chain, including increased market shares for breeders, premium prices for farmers, reduced costly imports for processors and low stable prices for consumers.
Information from the project will have wider health benefits in enabling bakers to reduce the levels of salt in bread and other food products. Salt is currently included at about 1.4% in bread (corresponding to 17% of the UK recommended daily intake) and affects the functional properties of dough by interacting with the gluten proteins as well as contributing to flavour. Reducing the salt content of dough results in a requirement for greater dough expansion during proving (as the dough sets at a lower temperature during baking), which in turn requires a more stable bubble structure. Consequently, improving the stability of gas bubbles in dough is a crucial stage in reducing the salt content of bread to the current target of about 50% of the current concentration. The use of fat and emulsifiers in baking is also widespread to improve gas cell stability, and their levels will also be reduced by increasing the natural stability of bread dough.
Therefore this research will benefit consumers and the health of the nation in the longer term, through the reduced intake of salt and fat.