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Functional and Biochemical Changes in Maturing Barley. I. Changes in Malting and Brewing Characteristics¹

Samples of ‘Larker,’ ‘Dickson,’ and ‘Conquest’ barleys (Hordeum vulgate L.) were harvested at 2 to 5 day intervals between 7 to 37 days after heading, dried to about 12% moisture, and threshed. During development, the kernel (dry) weight increased from about 12.5 to 33.0mg, the test weight from 29 to 59 kg/hl (22 to 45 lb/bushel), and the hull color (Agtron) decreased from about 90 to 50. Moisture contents of the field-harvested samples decreased almost linearly; net protein synthesis was apparently completed 10 to 13 days before field maturity. Maturation was accompanied by a percent decrease of ash, but increase of ash per kernel. Samples from early development stages imbibed more water in steeping, malted more slowly, and had higher malt losses. Malt modification, a-amylase, and protein solubility increased with barley maturation. Diastatic power, ß-amylase, and -amylase were lowest in malts from barleys harvested about 12 to 17 days after heading. No consistent varietal effects on compositional and functional patterns during maturation were established. Whereas compositional maturity was attained in barleys harvested with a moisture content of 41 to 44%, optimal functional properties required harvesting of barley with lower moisture.

Key Words: Germination • Test weight • Kernel weight • Color • Moisture • Ash • Protein • Wort • Extract • Amylases • Proteolytic activity

² Chemist in Charge, U. S. Department of Agriculture, and Professor, Agronomy Department, Univrersity of Wisconsin; Chemist, Barley and Malt Laboratory; and Professor, Agronomy Department, University of Wisconsin, Madison, respectively.

Received for publication July 22, 1970.