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Characterising Wheat Flour Protein Quality from REOMIXER Traces

HGCA PROJECT REPORT 324

Characterising Wheat Flour Protein Quality from REOMIXER Traces

by

C ANDERSON
Cereals and Milling Department, Campden & Chorleywood Food Research Association Group, Station Road, Chipping Campden, Glos. GL55 6LDPB

NOVEMBER 2004

Abstract

The project aim was to evaluate the ability of the Reomixer (a planetary pin mixer with computer interface designed to be similar to a Mixograph) to provide useful protein quality information, particularly for varietal testing in Recommended List (RL) and National List (NL) trials. The white flours from the 2001 and 2002 harvests were studied on the Reomixer. Other analytical data on the flours were also available.

The instrument provides practical, rapid small-scale wheat protein quality measurements derived from dough mixing characteristics. It was used with two recipes. These were 1) flour-SDS solution dough (SDS-dough) where SDS is sodium dodecyl sulphate, a detergent, and 2) flour-salt-water dough (standard-dough). The time to reach the peak of the mixing curve is taken from SDS-dough. The mixing curve data from standard-dough is reduced by calculation to two co-ordinates that are plotted on a quality map that discriminates between varying dough development, peak time, peak height and differing breakdown. Comparisons of the plotted positions of test samples are made with reference quality areas derived separately from established varieties or from a quality score (e.g. for breadmaking).

The peak time of the mixing curve from SDS-dough provided a dough strength measure that has the potential to replace the current strength measurement with the use of equipment of reduced capital cost. For breadmaking varieties, it enables assessment for weak and very strong gluten (less likely to be suitable for high energy dough mixing) and strong gluten (less likely to be suitable low energy dough mixing). For biscuit making varieties, it enables screening for relatively stronger dough (more likely to be acceptable).

For quality maps, the characteristic regions for the established varieties were determined. The relationship of position on the quality map with other individual flour quality parameters (e.g. loaf volume) showed trends in direction diagonally across the map. A quality area, plotting outside of which was definitely negative for overall bread score, was identified. Although plotting inside this area is not necessarily positive, virtually all the averaged values for the established RL varieties plotted in this area. A biscuit flour score region giving a very high likelihood of the required Extensograph resistance and extensibility was also found.

As an example, using varieties on the first year of National List testing, the Reomixer data was shown to have potential in providing relevant quality information from both recipes. The dough strengths of potential biscuit making varieties varied, with several below an indicated target for acceptance to the RL of 60 s: they also plotted outside the biscuit flour score region. Varied positions on the quality map were also observed for breadmaking varieties where they did not all correspond with the areas of the established varieties: some also plotted outside the bread quality region. This demonstrates that breeders could use the technique to better target varieties for National List testing. Use on National List varieties would provide additional information for decisions regarding selection for the Recommended List trials, thus ensuring use of HGCA funds for testing more appropriate varieties. Use across the varietal assessment chain (from breeders to millers) would allow direct comparison of values with improved understanding of quality requirements.

HGCA Project Number: 2531
Price: £6.00

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