unmaltable
/(ˌ)ʌnˈmɔːltəbl/ /(ˌ)ʌnˈmɒltəbl/adjective
Of barley or another grain: that cannot be malted.
Origin
Late 18th century; earliest use found in William Marshall (bap. 1745, d. 1818), agricultural writer and land agent. From un- + malt + -able.