Increasing competitiveness of home-grown wheats through improved methods for quality evaluation and optimised milling

Abstract

To ensure the competitiveness of U.K. wheats, it is important that they have the appropriate qualities to perform well in food processes, including breadmaking and biscuitmaking. To assist processors in identifying wheats of suitable quality at intake, small-scale tests are required with good capability to predict processing performance. Additionally, such tests are required by breeders to assist them in the development of new varieties with good processing characteristics. Limitations in the predictive capability of current small-scale tests have been recognised. The aim of this project was therefore to evaluate the performance of various flour quality tests and to identify new or modified tests that could provide a better prediction of the biscuitmaking and breadmaking potential of wheats.

The project demonstrated that many of the flour quality tests currently in use have the capability to distinguish the widely differing baking properties of nabim group 1 and 2 wheats from those of groups 3 and 4. However, test baking remains the most effective method of discriminating performance within these populations. For breadmaking performance, gel-protein rheology remains one of the most useful small-scale tests. It was shown that good results could be obtained with a low cost rheometer. However, the cost of sample preparation remains an obstacle to the widespread adoption of the test. Among rheological tests of dough, the Alveograph is not widely used in the U.K., except for export specification, but showed promise for prediction of breadmaking potential. The new Stable Micro Systems D/R instrument provided reasonable agreement with the Alveograph, and offers a promising alternative to it. An alternative Alveograph protocol was evaluated, using the new Consistograph instrument to produce doughs with adapted hydration levels. However, although these more closely reflect the optimum hydration levels for baking, greater discrimination of breadmaking potential was provided under the conventional, constant hydration test conditions. Enhanced interpretation of Alveograph data was obtained by calculating stress-strain characteristics from the normal curves, from which a new parameter was developed that gave a good discrimination between varieties of differing protein quality. More widespread adoption of this test in the U.K. may provide improved capability to predict breadmaking quality, used in combination with existing tests.

For semi-sweet biscuitmaking, soft group 3 and 4 wheats produced better quality biscuits than hard group 1 and 2 varieties, and could readily be distinguished from them by several tests. However, no effective prediction of quality within the group 3 and 4 wheats could be found, including methods currently relied on for this purpose.

Many of the rheological properties of doughs measured were partially determined by the water absorption of the flours used. To ensure consistent flour performance in baking processes, it is important for millers to produce flours to a consistent water absorption. The Farinograph is well suited to measurement of water absorption for breadmaking flours. However, for biscuitmaking, it provided inconsistent prediction of the water absorption measured more directly by extrusion of biscuit doughs, and a bias was seen between harvest years. An NIR calibration against the extrusion test provided better results. NIR calibrations for water absorption are already in use in industry, and introduction of a specific calibration for biscuit flours might provide more consistent performance than the use of a general-purpose calibration against the Farinograph for all flour types.