Lesson 6 - Malt Quality

We start with barley attributes that can affect how the malt performs in the malting process and in the brewery.

Variety

Any variety used for malting should be an approved malting variety. Some brewers and maltsters specify particular varieties. Approved varieties are selected to have the required agronomic and malting properties so should perform acceptably in the maltings. Even with approved varieties, there is variation from crop to crop and field to field that can influence the malting and brewing process. The maltster or brewer may need to adapt their process conditions to deal with these influences. Ensuring specifications are robust and are met by the grain, minimises the effects of this variation.

Nitrogen

Very dry weather during ear filling causes thin grains with higher nitrogen. The higher the nitrogen level in the soil, the higher the nitrogen level in the kernel. The level of extract is inversely proportional to the nitrogen level. In other words, the higher the nitrogen, the lower the amount of starch.

% protein = % nitrogen x 6.25

Example:

1.6% nitrogen malt

% protein = 1.6 x 6.25 = 10%

Why is nitrogen (protein) so important for beer?

Protein is broken down into small peptides and amino acids during malting and mashing. This is called free amino nitrogen (FAN) which is important for yeast nutrition and in turn effective fermentations. Less completely degraded protein, mainly in the form of polypeptides, stabilises beer foam. Protein and protein breakdown products are also believed to improve beer mouthfeel and fullness. Too much protein can cause hazes in beer and problems with beer filtration. 

Kernel size

Environmental factors such as drought or excessive rain during ear filling lead to small or uneven kernel size. Optimum rainfall during the ear filling stage produces plump and even sized kernels with good extract potential.

Kernel size is measured using a sieve with 2.2 mm holes. Smaller grains fall through the sieve, while larger, plumper grains are retained. We ideally want a high proportion of plumper grains (bearing in mind that six-row barley often has thinner kernels). Having more than 90% of plump grains gives the malting process the best chance to produce consistent malt. Consistent grain size is essential for milling with a roller mill as the gap size is set on the basis of grain size. Oversized grains are over crushed and undersized grains may not be crushed at all.