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Comparison of GFFF and LALLS methods for determination of large and small starch granules in spring barley grain (Hordeum vulgare L.)
Psota, V., Bohačenko, I., Chmelk, J., Hartmann, J.

A newly developed method GFFF (Gravitational Field-Flow Fractionation) and the well known method LALLS (Low Angle Laser Light Scattering) were used to assess content of starch granules in the grain endosperm of seven varieties of spring barley (Hordeum vulgare L.). As a distribution criterion, the ratio of starch granules larger than 8 μm (type A) and smaller than 8 μm (type B) was chosen. Both methods assigned the varieties Akcent and Forum to the variety set with the highest ratio of large and small starch granules. Other studied varieties (Amulet, Kompakt, Olbram, Scarlett, and Tolar) formed a statistically indiscernible variety set with a lower ratio of large and small starch granules. Statistically highly significant correlation between the GFFF and LALLS methods was proved (r = 0.782). Starch in barley caryopses occurs in a form of large (type A, 8-30 m) and small (type B, 2-8 m) granules. [14] Generally, the small granules represent ca 90 % of the total amount of the granules but only 10 % of the starch total weight. [1] During the technological process of the beer production, most granules are degraded to fermentable sugars which are converted by yeasts to alcohol. Due to their compactness, however, ca 5 % of starch granules remains inaccessible for enzymatic degradation. The small starch granules tend to embed firmly into the protein matrix and interior of the cell walls. [16] Besides the loss of yield at alcohol production, these spherical particles can cause further technological problems. They can create starch haze and block filter beds in lauter tuns. [23] A number of methods have been developed for measuring the starch granule distribution. [5, 10] The main techniques used are Image Analysis, the Coulter Counter method and the Low Angle Laser Light Scattering method (LALLS). Another method for measuring starch granule size distribution is the newly developed method of Gravitational Field-Flow Fractionation (GFFF). [3, 4, 9, 21]. These techniques allow to acquire more information on this aspect of starch. New data can then be utilized in breeding programs and for assessment of specific lots of barley or other cereals.

Descriptors: barley, starch granules, size distribution, LALLS, GFFF

BrewingScience - Monatsschrift fr Brauwissenschaft, 60 (March/April 2007), pp. 60-62