Last Runnings are usually rich in silicates, phosphates, polyphenols and nitrogenous components of high molecular weight. The latter two groups are potentially haze forming materials and should be avoided as far as is practicable.
Worts collected towards the end of the run-off are not very fermentable.
Last runnings have rather high pH because of their lesser buffering capacity.
Range of Values
The increase in pH of the last runnings is usually 0·2 – 0·7 units.
The gravity at which last runnings are discarded will be determined by experiencein the brewhouse. As a guide, when producing a beer of initial gravity 1040°, from an all malt grist, collection should be terminated at a gravity of 1004° to 1006°.
The temperature of sparge liquor will depend on brewing practice but normally starts at 74°C (165°F) and ends at 71°C (160°F).
Last runnings containing brown oily material (lipids) or substantial quantities of particulate material must be avoided.
Last runnings should not be carried over into subsequent brews.
The pH of the last runnings should be measured (see Topic 11).
The gravity of last runnings should be measured, using a hydrometer, at intervals of 10 minutes before the cut-off point.