In our first webinar Carl Heron, our master brewer, takes you through how to read a certificate of analysis (COA). We get asked about COAs on a regular basis by customers and it is the gateway to many discussions around milling, mashing and fermentation. A far from dry topic we hope and one that should hopefully stimulate a good few questions for us to jump into as we progress through the series.
The webinars are free to all, customers or otherwise and is now available to view on youtube.
The slides are available for download here
For a quick overview on your analysis, check out our Quality Malt Guide page.
We were posed several questions throughout the webinars. Check out our answers below.
Free α-amino nitrogen (FAN) is a measure of the low molecular weight substances derived from protein breakdown, mainly amino acids and small peptides, which are needed to support yeast growth and metabolism. It is generally agreed that FAN in all-malt wort of 100-140mg/litre will give healthy fermentation. Where non-malted cereals are used then higher levels (>150 mg/l) may be required.
A protein rest should really be called a peptidase rest. It is a temperature stand during mashing at 45-50’C to favour peptidase enzyme activity. Protein breakdown is really the job of the maltster and selecting the right and appropriate malting conditions should result in a balanced modified malt and an SNR of 38-42 (Kolbach Index of 40-44). An SNR less than 35 is an indication of under-modified malt and as such a protein rest would assist in the production of essential FAN (see above) which is required for yeast metabolism. Having a long protein stand at 45’C with a well-modified malt will almost always result in poor foam performance. However, if un-malted grains, sugar or syrup are used, these don’t introduce any amino acids to the wort and so FAN is diluted. This is where a protein rest would be beneficial to fermentation. It is important to remember that foam positive proteins are in-fact dissolved high molecular weight proteins. Their formation or release only occurs at temperatures above 55-60’C so protein rests below 50’C are only beneficial to produce FAN, not for head retention. A high protein / nitrogen malt doesn’t not necessitate a protein rest. Use the SNR and FAN values as a guide.
Yes. We set an internal specification for malt parameters for every type of malt we make. The specification can vary from year to year since many of them are determined by the barley. However, at Crisp, we are advantaged by two factors; working with farmers on long-term contracts who understand how their fields perform, and by the terroir of Norfolk which tends to produce easily modifiable, low nitrogen barley. We won’t accept barley into the maltings at harvest which doesn’t meet our specification.
This is another question which relates to FAN, but also to DP. Dark and black malts are roasted to high temperatures which denatures the enzymes in them. As a result, by using a high proportion of dark grains you run the risk of diluting the available enzyme pool which could result in under-attenuation of the beer. To combat this, don’t go too high with your speciality malt additions (no more than approx. 15-20%). You can, of course, lower the mashing temperature or lengthen the mash to favour β-amylase, the enzyme responsible for producing fermentable sugars. Dark grains also have low levels of FAN since the amino-acids are used up in the darkening chemical reactions. A dilution of the FAN pool can result in sluggish fermentation. To increase FAN in mashes with high levels of dark grains and adjuncts, consider a protein rest, increase Ca2+ ions or thicken the mash to increase peptidase activity (45-50’C). You might also add yeast nutrition or a high FAN malt.
Unfortunately not! If only we could it would make copper finings trials unnecessary. We suggest copper finings optimisation is carried out at every change of barley season and also if you switch malt supplier. Start with the standard recommended amount as advised by the copper finings supplier, then do trials +/- 10% and 25% to determine the optimal for cold break formation.
There is an empirical formula which provides a reasonably accurate conversion from the ASBC/EBC % extract to the IoB L°/kg unit. It is useful to remember, that EBC/ASBC worts are prepared using a temperature programmed mash which utilises a 45’C rest for 30 min, the mash is then raised to 70’C over 25 minutes and then a 70’C rest for 1hr. An IoB mash uses a 1hr 65’C rest. Therefore, the IoB and EBC/ASBC units are not perfectly convertible.
The formula for approximate conversion is as follows:
IoB (L°/kg) = (EBC (%)-1.705)/0.2586
DMS or Dimethyl sulphide is a volatile sulphur compound found in malt that has a low flavour threshold in beer of just 35ppb. Some lagers have values of 100 ppb DMS, but over this, the DMS gives a sweetcorn like flavour. Kilning is crucial to the reduction of the DMS precursor (DMS-P) in malt and higher kilning temperatures will reduce it.
We don’t necessarily agree with the whole “boil for 90 min” wisdom. Extra Pale Ale Malt, Extra Pale Maris Otter, Europils and German Pils Malt from Crisp tend to come in at <5ppm DMS-P which shouldn’t give any DMS character with a 60 min boil. Most lager malts are made this way these days, but it is always worth asking your maltster for the DMS-P spec if in doubt. For home brewers, remember to boil without a lid. Also, warm vigorous fermentation will drive off the volatile DMS. This is one reason that British Ales tend to have lower DMS levels.