Since 1870 we’ve lived and breathed malting. With this passion and expertise, and by combining traditional and modern techniques, we create an impressive range of malted and non-malted products, including several unique and exclusive barley malts.
There is nothing more we love than talking to brewers and distillers so if you have any questions, or would like to arrange a call with a member of our team, please feel free to get in touch – we would love to hear from you!
UK brewers are blessed by the quality of British malts. It’s well modified meaning we can utilise simple processes such as the Single Temperature Infusion Mash Tun. When using less well-modified malts or non-malted cereals a stepped mash may need to be utilised to add a beta-glucan and protein strand. Both enzymes are active below gelatinisation temperature, so the mash’s temperature needs to pass through different temperature stages. The traditional method for this is Decoction Mashing, where a proportion of the mash will be moved to a separate mash kettle and boiled before being returned to the main mash, raising the temperature. The decoction method can add flavour but it’s energy intensive and time sapping. The MCV allows stepped temperature mashes with reduced energy and cycle time.
Well, we all love a three-letter acronym and the MCV does not disappoint. It’s short for Mash Conversion Vessel. A single tank where the starch in the mash converts to fermentable sugars. It has no other job. It does not filter the mash, it does not boil it. It simply lets it convert under controllable and repeatable conditions.
Made from Stainless Steel they have a heating jacket, and a multi-speed mixer. After covering the base of the vessel with some foundation liquor, the mash enters via a hydrator. The grist and liquor are thoroughly mixed, reducing clumping and oxygen uptake. The hydrator helps the liquor to catch dust helping to increase extract recovery. The mixers are specially designed to limit any shear forces that could damage the mash, causing poor filterability. The paddles are large, sometimes offset and have adjustable rotation speeds – normally slow and slower! During mashing the mixer will be on a higher setting, but still running slow to avoid shear forces and oxygen pickup, but fast enough to keep the mash mixing and the temperature even.
When the grist stops flowing, and you have banged the grist case a few times to make sure its empty, the liquor will continue for a small amount of time to ensure the hydrator is flushed out. It’s important that the grist runs out before the water otherwise you will lose extract and form dough balls. The foundation liquor volume and the flush liquor volume need to be considered when working out the liquor-to-grist ratio. MCV’s will use a higher ratio (2.9 to 3.2 : 1) compared to the mash tun helping to increase extract recovery and reduce the viscosity of the mash, countering sheer forces and helping with filterability. Higher liquor-to-grist ratios will dilute the enzyme content of the malt, but running the mixer in slower-than-slow mode will eliminate any temperature fluctuations keeping the enzymes in their optimal temperature range helping to reduce the mash stand time.
The mashing temperature depends on the quality of malt and the general grist composition. High levels of beta glucans can be dealt with by adding a 45 to 50oC (113-122oF) step to the mash. But proteolytic enzymes are active at this temperature, and they will break down proteins increasing the malt modification. This can have detrimental results to the final beer as it can harm head retention and increase the FAN content resulting in colour pick up. The great head retention we see on decocted mashes most likely come from denatured proteins during the boiling step, not the protein rest. Mashing at 35oC (95oF) would get around this problem, but so would using some exogenous beta-glucanase from your favourite brewing supply company. In reality, most malts are suitable for ‘high temperature’ mashing (over 60oC, 140oF) so the temperature steps are usually optimised to create a consistent mash.
The consistency comes from automation. MCV’s are fitted with sensors, meters probes and timers all running to a program that makes sure the process is replicated on every brew. This can bring a headache when they eventually fail and fail they will. Anyway, if the strike temperature is a little low, the heating jackets will come on and warm the mash. There is always a little overshoot so they should turn off about 0.5°C below setpoint. During the mash stand the mixer will run on slower than slow speed and the heating jackets could come on if the temperature drops below the set point. If the heating jackets come on the mixer speed would increase to slow. You can have several stand times at several different temperatures on the way up to 72oC (161.6oF), which is an important temperature. Malt is made up of large and small starch granules. Larger ones gelatinise easily about 60oC (140oF and crop year dependent) but the smaller ones only gelatinise over 70oC (158oF). If left unconverted these can cause filtration and attenuation issues. Luckily alpha-amylase is still active at 72°C (161.6oF) so problems averted. At the end of the 72oC (161.6oF) stand the next temperature rise will fix the sugar spectrum of the wort. There is normally a manual input before the rise commences and this is when you would check the mash for conversion using starch.
The final temperature depends on your thought process. 74-75oC (165.2-167oF) may extract less tannins from the mash but 77-78oC (170.6-172.4oF) will reduce the wort viscosity aiding filtration. Some of the larger brewers use the lower temperature in combination with a mash filter, could the mechanical squeeze extract more of these tannins if the wort was a higher temperature? And the more traditional breweries with a lauter would use the higher temperature. Some use as high as 80oC (176oF) with no issues. If extracting tannins concerns you, think about using some Crisp Clear Choice malt. It does not have any so you can have the best of both worlds.
About Me
Mike is the sales manager for Wales and the West of England and is located in Wigan.
You can read my bio by clicking the button below
So, MCV’s allow the brewer to have stepped mash without needing time and extra vessels to do a decoction mash. But you don’t have to do a stepped mash, everyone can benefit from the improved extract recovery, consistent wort quality and reduced process times and energy use. Yes, the capital costs are higher than a mash tun and when the mash flow meter fails causing the vessel to overflow causing a hell of a mess it a little demoralising (I’m sure this would not happen on a modern system) but the pros outnumber the cons.
Back to top
