tørstoff

Tørstoff is a term used in Norwegian and Danish that refers to the portion of a substance that remains after most of the water has been removed. In practice, it is synonymous with dry matter (DM) and is a key concept in nutrition, agriculture and food analysis. Dry matter represents the non-water portion of a material and is used to express nutrient content on a standard basis.

Measurement of tørstoff follows standard laboratory methods. The most common procedure is oven-drying a sample at about 103–105°C until a constant weight is reached. The dry matter percentage is calculated as (dry weight / original fresh weight) × 100. Some laboratories use alternative approaches such as infrared drying or freeze-drying, but oven-drying at 105°C is widely used for comparability. For some materials, drying can cause loss of volatiles, which may bias results, so method choice and interpretation should consider the material’s properties.

Applications and interpretation: Dry matter content influences energy density, shelf life, texture and handling properties. In animal feeds, DM basis is used to report nutritional values and to formulate rations. Typical ranges give a sense of composition: fresh forage typically contains about 15–25% DM (75–85% moisture), hay about 88–92% DM, and silage around 25–40% DM. Reporting on a tørstoff/DM basis facilitates comparisons across products with different moisture levels and supports standardized nutritional labeling.