Brewing on a Commercial System
31 Jul 2014
Home brewers are known for their tendency to worry. We worry about small things that you can't see like bacteria, wild yeast and oxygen. And we worry about our actions and their eventual outcomes. You only have to take a quick tour of sites like Home Brew Talk or Realbeer to see first hand what Im talking about. Thats because there are so many things that can go wrong. At every single stage of the process there is an opportunity for disaster. Hours of labour and personal energy can be destroyed in an instant from something as simple as equipment failure or power cuts to something more complex like yeast metabolism and growth. Knowing best the risks involved and doing everything you can to provide a perfect environment for success is what brewing is all about. After all is said and done its the yeast that make the beer, not the brewer! I recently had the opportunity to see that professional brewers have a LOT more to worry about than home brewers and a lot of the little worries have real potential to become big problems that cost real money.
This is Scott's Brewing Co's 2500L (or 25 Bbl) combi system. It's a combi system because the mash tun and the hot liquor tank are on the left and part of the same vessel. With the help of brewers Phillip Scott Jess Wolfgang, together we used this equipment to brew 2400L of my Frontier Extra Stout recipe and with that, the official start to Sparks Brewing. The system has a Gas fired kettle and an electric hot liquor tank with two 25,000 watt elements installed. The controls for this beast are surprisingly much the same as what Ive been staring at for the last few months while building my electric system, but the cables are all thicker and the components much more industrial (and expensive!)
On the right you can see the controls for various pumps in the brewhouse as well as heating For both vessels.
The first thing to do once I arrived at Scotts was to make sure the water report I had received was at least somewhat accurate. Prior to being here I had received a water report from Phil and using this I had created a water profile that would suit the stout we were about to make. Since every brewery around the country has a different water source, knowing how to adjust and measure the levels of certain ions in the water is an invaluable tool for the contract brewer looking to best replicate his recipes. Brewing beer without this information at hand is just not good enough. While entering competitions as a home brewer I quickly learned that knowing your water and adjusting it to taste can take a beer from good to world class. After all, its the seasoning that determines the balance of flavours in any culinary discipline. We have very soft water in Auckland and Im lucky enough to receive a supply that is relatively low in any chlorine. Scotts water source is even cleaner and actually quite close to what Im used too. A quick titration of the water gives me an indication of a) How accurate the water report is i.e. how much alkalinity Im dealing with and b) how much acid I need to adjust my sparge liquor later on.
Next we start to scale up the recipe based on the predicted efficiency of Scotts System. I used Beersmith throughout this brew day as its what Im used to as a home brewer and I have to take my hat off to Brad Smith (the software developer) because it was so easy to use! I setup an equipment profile in Beersmith and plugged in a conservative %70 total brewhouse efficiency. Added the equipment sizes and batch size, fermenter losses boil off etc. Then use the scale function within your recipe, select the equipment profile and your done.
At first the suggested mash water exceeded the hot liquor tanks capacity, so we adjusted the water/grist ratio down a little till we got within the volume we needed which was 1800L. Next one of the more physical aspects of brewing commercially was underway, filling the mill hopper. The hopper is directly attached to the mill and we used a forklift to raise the many bags of malt that are needed. For this batch of stout we used 20 bags (500KG) of local base malt from Gladfield. We then added 200KG of various specialty malts and the mill was pretty much full to the brim!
The mill is turned on and the auger started. The Auger transfers the grain from the bottom of the mill to the top of the mash tun where it is mixed with water as it goes in.
The powerful motor turns a long auger that sits within the pipe. This delivers the grain to the mash tun.
The bottom of the mill is slowly opened with this great little wheel (there's something kind of circus circus about it)! The grain can flow through the mill and the gap size can be adjusted if the crush isn't quite right. This is just about right!
The tiny wheel holding back almost a tonne of grain!
Once the grain hits the mash tun the mash rakes are turned on and hot liquor is forced into a 'grist hydrator' which spins the water and mixes the grain into a homogenous mash that is completely free of clumps and dough balls. As a home brewer Im often stirring and working the mash to make sure none of the grain is clumped together, this great little time saving device is a must when you physically can't get into the mash tun and the size of the mash itself is just too big to manually mix.
The auger is connected to the hydrator. Water comes in the side and spins around as crushed grain enters from above. The mash rakes slowly turn, lifting and repositioning the grain bed rather than mixing as one would imagine.
Mashing in on this scale takes some time and careful attention needs to be made in terms of the final rest temperature. Its difficult to shift the mash temperature once the rest has begun, and the base malt form New Zealand has so much enzyme that it converts almost instantly. Unlike home brewing where a pitcher of cold/hot water can change the mash temp quickly on a commercial scale you have to get it right as it happens. Within minutes the complex chains of fermentable sugars are combined, determining the eventual body of the beer. We hit a rest temperature of 65C which is exactly where I wanted it. This should leave some body in the finished beer but still come across as dry. As the mash-in gets to about half way, I measure out the salts from my water recipe and add these to the mash. This addition is mostly to buffer the PH drop that is expected from a grain bill so high in roasted malts. The roast malts free phosphates when they are combined with water, these phosphates react with calcium and magnesium to release two protons as H+. This free atomic hydrogen (hydron) drastically lowers the PH to below 5 which can cause problems for sugar conversion and flavour balance when the beer is complete. The enzymes responsible for converting starch to sugar work best within the range of 5.2 and 5.6 and the flavours for my recipe seem to be best balanced at a final beer ph of around 4.4. Any lower and the beer can come across as sharp or even acrid.
Our Mash PH reads 5.1 The temperature of the mash causes the meter to read .3 lower than it actually is so our reading is actually 5.4 which is spot on.
Unlike home brewing, volumes of this size hold their heat very well. At home we need to either have a well insulated mash tun or apply direct/indirect heat to the mash in order to hold a set rest temperature. I recirculate the wort through a heat exchanger that sits inside the hot liquor tank. At Scott's the sheer volume of hot mash holds itself in the zone just fine. After a 20 minute rest the wort is slowly recirculated from the bottom and back to the top of the mash, this clarifies the wort as it slowly filters through the grain bed. After 20 minutes of recirculation the sparge (rinsing of the grains) begins. As the wort is pumped from the mash tun to the kettle, hot liquor is pumped onto the top of the grain bed which trickles down through the grain collecting as much sugar as possible while en route to the kettle.
The Mash rest temperature is 65c while on the right the sparge commences by spraying hot water on top of the mash through this internal manifold.
As the sparge continues we monitor the specific gravity of the wort and the PH. Paying careful attention that the sparge liquor isn't above 5.6 as anything above this can start to extract tannin form the grain. If this was a pale beer I would have treated the water with acid to make sure this didn't happen, but all the roasted malts in the mash accomplish the same thing and our PH never goes above that threshold.
As the kettle fills I add the remainder of the salts from my water recipe.
Rather than add these to the mash with the initial addition (which would have dropped the ph far too low) I add these directly to the kettle, essential to balance the flavor. We continue to fill the kettle until one of thee things happens. 1) We hit out target pre boil gravity 2) our sparge runnings show a gravity of less than 1.009 3) The ph of the sparge liquor rises above 5.6. Stopping because of either 2 or 3 is not ideal as it probably means you've missed your target volume in to the kettle. Fortunately I had estimated our efficiency on the low side so we collect 2400L of wort and hit our pre boil gravity bang on.
Taking notes at every step... Customs require detailed accounts of everything so that they can verify how much alcohol is produced. Since things are different brewing on this large scale some adjustments are made throughout the day and its hard to remember by the time you get up the next morning!!
The kettle is direct fired with a 300kw burner. The kettle itself is lined internally with ceramics so even when the flame form the burner is out, there is still a significant amount of heat being generated. The boil comes to a head and a few quick sprays of water prevent it form overflowing out the top. This is actually one of the more dangerous moments in the brewhouse. Im sure every home brewer has experienced a boil over which on our scale just makes a mess and is an annoyance more than anything else. On this scale the outcome can be disastrous. The controls to turn off the heat are located next to the kettle and with hot liquid shooting out the top of the kettle there is a real danger that the brewer could be hurt by such an event. Phil has learned the hard way that you don't seal the kettle lid and turn your attention away!!!
Keeping an eye on the kettle as it comes to a boil
After about 20 minutes of boiling we add our first addition of Hops (Southern Cross). While the boil commences Jess and Phil prepare the fermenter. After use the tanks are cleaned in place and sanitised. Then on the day they are given another dose of sanitiser before being plumed to the heat exchanger and ready for the incoming wort.
Jess hooks up some hoses and gives the fermenter a quick sanitise ahead of receiving our precious (expensive) wort.
Toward the end of the boil we add our Koppaflok (fining agent made form seaweed) and yeast nutrient, boil a little more and then kill the heat. This is when I add the lions share of the hops. 5KG of Styrian Goldings and 1KG of Kohatu. These are no more than a month off the bines and they smell incredible! I notice a distinct freshness from bulk bags that you just don't find in the little home-brew sized bags. Being able to order direct from the supplier means I can find out when the hops were picked and I can make sure that I get this years harvest.
The hops go in, a few valves are turned and we switch on the pump to recirculate the wort back into the kettle, this creates a whirlpool and further distributes the hops throughout the wort as well as bringing all the proteins and grub that we don't want to collect into the centre of the kettle. We can then draw off the wort from the side leaving all the junk behind.
The heat exchanger has two stages. The first is plumbed with cold water form the municipal supply and then the second stage is plumbed with glycol at -2 degrees. The flow of wort is then adjusted to reach the desired temperature going into the fermenter. Here we started off a little cold so we increased the flow of wort till we hit 18 degrees. The oxygen is turned on and injected into the wort on the outlet of the heat exchanger.
Heat Exchanger showing the two stages with the red hose being ground water and the yellow hose being glycol, this outputs the wort at just the right temperature
Once the kettle is empty we can pitch the yeast. We had a very full tank and some foaming which makes adding yeast in one of the top man way's impossible. So we rigged up a corny keg with some wort and first rehydrated in this before pushing it into the fermenter with c02.
The next morning the beer is bubbling away and temperatures are stable at 18C.