Relative Humidity (rh)

Relative Humidity (rh). The ratio of the actual moisture content (q.v.) of air at a given temperature (q.v.) and atmospheric pressure to its potential moisture content at saturation (q.v.) under the same conditions. It is commonly expressed as a percent (q.v.): for example, 75% rh indicates that air with a moisture content at this level contains 75% of the moisture it is capable of holding at saturation (q.v.) at the same temperature. Relative humidity is an important environmental factor during dough processing and needs to be closely controlled to avoid dry skin formation on raw dough pieces. It is measured by various types of hygrometers (q.v.), the one most commonly used in bakeries being the psychrometer (q.v.), also referred to as the wet-and-dry-bulb thermometer (q.v.).