Lesson 4 - The Mashing Process
This lesson discusses the process of mashing. It provides an overview and sets out the objectives of the process before explaining what parameters need to be controlled to ensure success. It describes the various methods used to mash and their impact on the wort produced. Finally, it details the composition of wort produced by mashing.
Grist Composition
It should perhaps go without saying that our mash will only be as good as our grist. The quality of the malt and the effectiveness of the milling operation are essential for successful mashing.
Malt modification
The journey from starch granules embedded in a protein matrix locked within a cell wall in a barley endosperm to maltose dissolved in nutritious wort is made up of two main steps. These are the modification of the malt endosperm in germination and the conversion of endosperm material in mashing. The extent to which the first step (modification) is complete affects what we need to do in the second step (mashing).
In a well-modified malt, the starch granules will be exposed, the cell wall material and protein matrix will be extensively degraded. This means a simple mashing process can be used to gelatinise and then hydrolyse the starch granules.
In under modified malt, the cell wall material and protein matrix are not broken down to the same extent, so our mashing process must incorporate steps that allow the enzymes required to degrade them to operate close to their optimum conditions. We also have the option of adding exogenous enzymes to assist with the breakdown of proteins and cell wall components.
Key to successful mashing is obtaining a consistent supply of malt and matching the process used to its degree of modification. That said, even the best devised mashing regime cannot successfully process very poorly modified malt or malt batches that are a blend of over and under modified grains.
Milling
Milling is controlled primarily to provide the right particle size distribution for the wort separation equipment being used. However, it also affects the mashing process. The more finely milled the grist is, the more substrate is exposed and the easier it is for the enzymes to access it. This leads to more rapid and extensive conversion. The yield of fermentable extract increases roughly in proportion with the reduction in particle size in the grist.
Adjuncts
Adjuncts do not contain enzymes, so the more we use, the lower the concentration of enzymes in the mash. Malt typically provides more enzymes than are needed to convert its own starch, so we can use adjuncts up to 30% of the grist by weight without encountering problems. Selecting malt with a high diastatic power or supplementing the malt enzymes with exogenous enzymes can help to reduce the risk of poor extract recovery. For adjuncts with starch gelatinisation temperatures above that of barley large starch granules, we either need to use pre-gelatinised products or gelatinise the starch separately in a cereal cooker. We will provide more information on that later in the lesson.