couch

In malting, the couch is a layer of steeped barley spread across a malting floor, typically 30 to 60 centimeters deep, where the grain germinates over several days. The barley has been soaked in water for 48 to 72 hours before being spread, and the couch provides the controlled environment where roots and shoots emerge. The term also refers to the floor itself, the physical workspace where this crucial transformation happens.

The depth and density of the couch must be managed carefully. Too shallow and the barley dries out; too deep and the center fails to aerate properly, encouraging mold and uneven germination. Malsters regularly turn the couch with hand tools or mechanical turners to prevent compaction, maintain even moisture, and expose all grains to air. This turning happens daily or every other day, depending on temperature and the malt style being produced.

Couch conditions and results

Temperature control is critical. The couch generates its own heat as seeds respire and root systems develop, so ambient air temperature in the malthouse must be kept between 13 and 18 degrees Celsius to prevent runaway germination. Humidity is equally important, typically held at 55 to 65 percent to keep the grain from drying while avoiding excess moisture that causes disease. When conditions are wrong, rootlets may rot, shoots may grow too long and tangle, or germination may arrest entirely.

The couch phase lasts 4 to 8 days depending on barley variety, desired enzyme development, and final malt style. Brewers and distillers specify couch parameters because germination depth and rootlet development directly affect the enzymatic power of the finished malt. Once germination has proceeded far enough, the green malt is transferred to a kiln for drying, which stops the process and develops color and flavor through heat.

The word couch comes from the Old French couche, meaning to lay down or a bed. In malting it has been used since at least the 17th century, and remains standard terminology in traditional floor malting operations, though modern industrial malthouses now use drum malters and air conditioning systems that reduce reliance on open couches.