Degree Lintner
°Lintner or degrees Lintner is a unit used to measure the ability of a malt to reduce starch to sugar, that is, its diastatic power. Degrees Lintner is an intensive unit, not an extensive one; it is independent of the quantity of malt used. While the measurement is applicable to any amylase, in general it refers to the combined α-amylase and β-amylase used in brewing. The term is also generalized to diastatic malt extracts and separately prepared brewing enzymes. The abbreviation °L is official, but in brewing applications it may conflict with °L used for degrees Lovibond.
JECFA, the Joint FAO/WHO Expert Committee on Food Additives, defines the degree Lintner as follows:
Note that the amylases used in brewing reach their peak efficiencies around 66 °C.
One can convert this definition to the number of international enzyme units per gram of grain, for example. Maltose, the main sugar produced in mashing, is a disaccharide of glucose with one reducing equivalent. One maltose will reduce two Cu2+ in the Fehling reaction. The concentration of Cu2+ in Fehling’s solution is 0.14 M, which is capable of oxidizing 0.070 M maltose. 5 mL of Fehling’s solution can oxidize 0.070 M x 0.005 L = 0.00035 moles of maltose. A 100 °L malt extract produces 0.00035 mol maltose in 60 min, or 5.8 μmol/min, or 5.8 IU of enzyme activity in 0.1 mL of a 5 g/100 mL infusion. The 0.1 mL of this infusion is equivalent to 0.005 g of malt. Therefore, 5.8 IU/0.005 g of malt = 1160 IU/gram of malt. 100 °L is equivalent to 1160 IU per gram of malt. This value is useful if alternatives to Fehling's reaction are being used to determine the amylase activity.
Evaluation of a malt or extract is usually done by the manufacturer rather than by the end user; as a rule of thumb, the total grain bill of a mash should have a diastatic power of at least 40 °L in order to guarantee efficient conversion of all the starches in the mash to sugars.
The most active barley malts currently available have a diastatic activity of 110 - 160 °Lintner.
In Europe, diastatic activity is often stated in Windisch–Kolbach units. These are related approximately to °Lintner by: