Lesson 4 - Adjunct Composition and Application
This lesson explores adjuncts, which are sources of fermentable extract other than malted barley. It investigates the different cereals that we can use as a starch source within the brewhouse and examines how these same cereals can produce liquid adjuncts. It also considers other sources of fermentable sugars that we can add either directly into the kettle or later in the brewing process.
Quality Analysis of Liquid Adjuncts
As a brewer, the analysis sheet for the liquid adjunct should guide how and how much of the product you use. Let’s look into two of the main parameters measured in the analysis of syrups.
Dextrose equivalent
When producing sugar syrups from starch, the DE is the extent to which the starch molecules have been converted to sugar. To understand this, we need to know what a reducing sugar is. Chemically speaking, reduction is the opposite of oxidation and involves donating electrons to other molecules. Because dextrose has a free aldehyde group (reducing end), it can donate electrons and hence acts as a reducing sugar. When one dextrose molecule is joined to another, the free aldehyde group is changed into the bond between the two sugars. In starch molecules, all the reducing ends are involved in the bonds between the dextrose monomers. So DE can be thought of as the percentage of reducing end-groups within the aqueous sugar mixture, relative to those within a pure dextrose solution. The DEs of some carbohydrates are as follows:
-
Pure starch is zero.
-
Dextrose/glucose is 100%.
-
Dextrins vary between 1 and 13%.
-
Maltodextrins vary between 3 and 20%.
-
Maltose is 52%.
The standard method for measuring DE in syrups is Lane-Eynon titration. In this titration, the ability of the sugar to reduce copper sulphate is measured. The Lane-Eynon titration is uncommon in the brewing industry. As brewers, the DE does not tell us everything we need to know as a syrup may have a high DE due to the presence of a high proportion of dextrose, but have relatively low fermentability due to the rest of the syrup being largely made up of dextrins. A full breakdown of the carbohydrate spectrum is of more practical use.
Brix
Brix is a scale very similar to Plato, and represents the w/w % of sucrose in a solution (1% brix is 1 g of sucrose in 99 g of water). Brix is expressed as % or °Brix, and is measured using a refractometer. A refractometer works on the basis that when light passes through a clear liquid it is refracted (bent) to a certain extent. The greater the amount of dissolved substance, the greater the degree of refraction.
As well as the above analyses, manufacturers who supply the brewing industry will also measure parameters similar to those we saw earlier in the malt lesson, such as colour, pH, % extract, or L°/kg. The table below shows the analysis sheet for a commercially available high maltose syrup.
Table: Analytical specification of high maltose syrup
|
Parameter |
Minimum |
Maximum |
Method |
|
Appearance |
Colourless to high yellow coloured syrup |
Colourless to high yellow coloured syrup |
Visual |
|
Dextrose Equivalent / DE |
40 |
46 |
Lane-Eynon |
|
Maltose % |
40 |
48 |
HPLC |
|
Brix° at 25°C |
78 |
84 |
Refractometer |
|
SO2 PPM |
200 PPM |
400 PPM |
Iodine Titration |
|
Sulphated Ash |
0.1 |
0.3 |
Furnace |
|
pH of (1:1 Aqueous Solution) at 25°C |
4 |
6 |
pH Meter |
|
Arsenic mg/kg |
|
1.0 Max |
IP Method |
|
Heavy Metals (Lead mg/kg) |
|
1.0 Max |
IP Method |
|
Total Plate Count |
2,500 cfu/gm Max |
Plate Method |
|
|
Yeasts & Moulds |
100/gm Max |
Plate Method |
|
|
E. coli |
Absent/10 gm |
Plate Method |
|
|
Salmonella |
Absent/25 gm |
Plate Method |
Take some time to investigate for yourself what a typical supplier certificate of analysis (CoA) looks like for the various brewing liquid adjuncts. An online search or a look through the records in the brewing office should provide you with a wealth of information and with the benefit of this lesson, it should all now make sense.