Development of a quality control method based on light transmission for predicting the quality of barley for malting

Abstract

A critical part of the malting process is the conversion of the grain endosperm from a hard, tightly packed reserve of protein and starch to a friable, easily digested material. This depends on the activity of the embryo and aleurone to generate the appropriate enzymes and an endosperm structure that will permit the passage of water and hence these enzymes to the cell walls and small starch granules. If either of these fails then the grain will not modify properly and the malt quality will not be such as to allow subsequent trouble free processing.

Although there are many ways to assess embryo quality there is no simple, robust and quantitative method which can identify the appropriate quality of endosperm structure. A meter has been designed and produced at BRI to quickly measure these features of endosperm structure. The principle is based on the transmission of light through whole husked grains. As a test of grain quality, the light transmission (LTm) meter is quick, simple, quantitative and robust with good repeatability and is non-destructive.

Conclusions

The LTm meter can measure the proportions of meali/steeliness in a barley grain with excellent correlation with visual assessment.
There was no evidence that the LTm of barley could predict extract or friability but measurements during steeping did give an indication of water uptake.
There was a poor correlation between barley LTm and malt calcofluor values.
There were more significant simple correlations between malt LTm (especially the median value) and malt extract, friability and calcofluor modification.
For a single variety, the LTm can show the proportion of chit malt and may be able to indicate extract potential.
Implications

The LTm meter gives an indication of the structural qualities of grain, barley and malt, endosperm. Data logging techniques allow the analysis and recording of each individual grain separately so the homogeneity of the sample is also determined.

The LTm meter could be used in a malting laboratory as an analysis of endosperm structure in either barley or malt. It could possibly replace other methods which are time-consuming and rely on visual judgement (e.g. farinator). An accurate measurement of the major fraction of the barley i.e. mealy or steely, will enable maltsters to provide optimal malting conditions for a grain type. The LTm meter is also able to assess malt endosperm structure in a similarly effective manner. Although all of the work here described is related to barley or malt quality, the method is also able to reveal internal structure in wheat.