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Corn Size Distribution, Cold Water Extract, and Diastatic Power in Relation to Malted Barley Quality

MBAA TQ doi:10.1094/TQ-46-1-0226-01  |  VIEW ARTICLE

Reginald C. Agu. The Scotch Whisky Research Institute, Research Avenue North, Riccarton, Edinburgh, EH14 4AP, Scotland, UK.

Abstract
The results of this study provide more evidence that when barley corns of different sizes are mixed together in a germination box during malting, homogeneous modification is difficult to achieve. A very strong negative relationship (R = –0.73) was found when the percentage of thin corns (<2.2-mm sieve) was correlated with diastatic power (DP) development. When correlation between the percentage of intermediate corns (2.2-mm sieve) and DP was performed, a similarly strong negative correlation resulted (R = –0.63). The study also showed that as the corn size distribution in barley malt decreased from higher percentages of thin (<2.2-mm sieve) or intermediate (2.2-mm sieve) corns to lower percentages, implying a higher percentage of large corns (2.8- to 2.5-mm sieve), the correlation results moved from a negative to a positive correlation, because the relationship between DP and large corns were strongly positively correlated (R = 0.69). Furthermore, the relationship between cold water extract (CWE) and corn size distribution showed that thin and intermediate corns modified at a faster rate, because a direct relationship was found between CWE and thin (<2.2 mm) and intermediate (2.2 mm) corns, corresponding to R = 0.47 and 0.43, respectively. In contrast, large corns modified at a slower rate, producing a negative inverse relationship between large corn size and CWE (R = –0.49).

Keywords: barley, cold water extract, corn size, diastatic power, malt quality 

Síntesis
Los resultados de este estudio se suman a la evidencia que demuestra que se dificulta llevar a cabo una modificación homogénea en el malteo cuando granos de cebada de diferentes tamaños se mezclan en una caja de germinación. Se consiguió una correlación fuertemente negativa (R = –0.73) entre el porcentaje de granos finos (cedazo de <2.2 mm) y el desarrollo del poder diastástico (DP). Hubo una correlación similar (R = –0.63) entre el porcentaje de granos intermedios (2.2 mm) y el desarrollo del DP. El estudio también demostró que al bajar los porcentajes de granos finos y de granos intermedios, es decir, al aumentar el porcentaje de granos mayores (2.5–2.8 mm), la correlación pasaba de negativo a positivo debido a que la relación entre el porcentaje de granos mayores y el DP es fuertemente positiva (R = 0.69). Es más, se obtuvo una correlación positiva entre el extracto en agua fría (CWE) y granos finos o granos intermedios (R = 0.47 y R = 0.43, respectivamente), demostrando que los granos finos e intermedios se modifican a una mayor velocidad que los granos mayores que mostraron una correlación negativa entre el tamaño y el CWE (R = –0.49).

Palabras claves: calidad de malta, cebada, CWE (extracto agua fría), poder diastástico, tamaño de grano

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