Making ice beer out of leftover ingredients--recipe and brewday

Eis beer, ice beer, eisbier--whatever you want to call it. These beers bring up two types of beers. One, the refined eisbocks that turn doppelbocks into concentrated maltbombs. (For example, the sought after eisbocks made by Kuhnhenn.) Two, those industrial lagers floated in the 1990s with a little more alcohol with Ice in the name. (E.g. Bud Ice.) In both cases the beers are made using freeze concentration--often referred to as freeze distillation--by removing some of the water content to concentrate the alcohol and other compounds in the beer. Homebrewers often limit themselves to the more refined aspect making eisbocks--but what if we toured the technique with other styles and ingredients? Let's find out.

This project began as a way to try to use up leftover grains to turnover my supply of grain. Anybody buying grain by the pound instead of by the recipe ends up with these bits of grain that go unused. Most of these leftovers beers inevitably become some kind of beer best described as brown because they end up with a long list of darker specialty malts will produce a beer that is both brown in color and sort of muddy with overlapping sweet, dark malt flavors. My own grain supply suggested the same. Rather than produce some mediocre brown ale I decided to use the grain for another potentially fun experiment. After looking at the grain with the goal of using as much as possible I came up with this recipe that is somewhere in the vicinity of maybe an unusual porter. Rather than drink a couple gallons of muddy brown beer I thought it might be interesting to try concentrating the beer with freeze concentration and see if the concentration developed something more interesting.

Freeze concentrating homebrew

Typically homebrewers use this process to create eisbocks, considered the original ice beer. Eisbocks are doppelbocks partially frozen using a freeze concentration to boost the beer from a high single digit lager to a double digit maltbomb. In the 2000s a beer in the double digit ABV was an extremist's beer but today it's a common range for imperial stouts, barleywines and other strong beers. Today's strong ales tend to rely upon a wort with extremely high starting gravity forced to ferment out but still leaving behind a finishing gravity with enough sugar to make a 4-5% ABV beer. Eisbocks and other freeze concentrated beers ferment into a high single digit ABV but undergo a freezing process to create less beer with more punch. 

I don't pretend to be an expert on freeze concentrating homebrew but it's an easy process. I've only tried freeze concentrating homebrew once very early in my homebrewing. It was ok but at the time I only had an apartment freezer which didn't get especially cold. The concept is simple--you freeze beer. If you've ever put a bottle of vodka in the freezer you know it doesn't freeze in residential freezers. That's because alcohol freezes at -173.2F. The water in the beer starts freezing at 32F so as the beer cools in a freezer the water freezes while the alcohol doesn't. The water tends to freeze on the perimeter of the beer volume while the alcohol mostly stays in the core of the vessel. You then drain the vessel quickly so the water stays frozen and you extract a more concentrated beer. Not only is the alcohol more concentrated but the flavor compounds as well so the beer becomes more potent all the way around.

In practice, it is slightly more complex. The relationship between water and ethanol makes for an imperfect freeze. Water and ethanol bond so you may lose a little ethanol to the ice crystalization and the solution cannot so thoroughly freeze in a residential freezer than you can remove so much water that you will reach a high concentration of alcohol. The colder the freezer the more water can be frozen and produce greater concentration. In a typical fridge/freezer combo the concentration is minimal, in a colder chest freezer more concentration. For most homebrewers freeze concentrating beyond the mid teens in ABV will be difficult without access to commercial freezers. 

Temperature (F/C).......% Alc.
............10 / -12.2.........8
.............5 / -15.0.........11
.............0 / -17.8.........14
...........-5 / -20.6......... 17
.........-10 / -23.3..........20
.........-15 / -26.1..........24
.........-20 / -28.9..........27
.........-25 / -31.7..........30
.........-30 / -34.4..........33

Of course, the safety concern here is that freezing liquid expands so no glass should be used as a vessel for freezing. Small batches can be done in empty plastic water or milk jugs while buckets are common vessels used for larger vessels. 

Using plastic jugs the process is extremely simple. Rack the fermented beer into jugs and place them in the freezer. Over a few hours to days the beer will turn slushy and under the right circumstances may form a solid ice block with a liquid core. The jugs are then inverted over another vessel to drain the liquid. With time the ice will begin to thaw so you have to make a judgment call on how much liquid you want to extract. Many discussions around the internet suggest leaving behind 30-50% of the volume by the time the liquid is removed and most of the ice remains. The remaining beer can be further aged or packaged immediately. 

With this process in mind, let's look at the leftovers recipe and then walk through the process below. 

Designing the leftover ingredients homebrew recipe

When designing recipes out of leftover ingredients it's hard to balance hitting to goal of using as much old supply as possible while not creating a beer with more than a muddy brown character. Thankfully most of the older ingredients I had to use are base malts with small amounts of various crystal malts. A hodgepodge of pilsner, maris otter, vienna and munich isn't too far off from a complete doppelbock recipe. Adding a little crystal malt wouldn't be too crazy although unnecessary. I also had a little chocolate malt which will add a little roast that should help cut the sweetness supplied by the crystal malts. Overally, the end result is a recipe that is definitely not stylistically a doppelbock but not so far removed that it should be unrecognizable as an eisbock when it reaches its final destination. 

Most resources on creating eisbock and other freeze concentrated beers is to start with a clean, malty beer because the concentration process is concentrating everything in the beer except water. That means bitterness, yeast compounds, flaws, etc. are all magnified. What might have been below the taste threshold pre-concentration may emerge after. For this reason clean, malty doppelbocks are easy base beers for the technique. To that end, I've also elected to ferment the beer with lager yeast to maintain a neutral fermentation character. Generally doppelbocks are hopped at a very low amount in BU:GU ratio which, after concentration, leads to an even sweeter beer. In the interest of creating some balance to the beer I bumped up the bitterness well above normal doppelbock targets so the final product isn't completely syrupy. 

Well, let's get this thing started.

Leftovers Ice Beer Homebrew Recipe

Details
Batch Size: 2 gallon
Est. ABV: 8.3%
Est. IBU 36
Est. OG: 1.077
Est. FG: 1.015
Est. SRM: 30
Expected Efficiency: 72%
Grain Bill	Pounds		Ounces		SRM		Pct. Grist
Pilsner malt	1		8		2		26.10%
Vienna malt	1		9		3.5		27.10%
Munich malt	1		2		9		19.70%
Maris Otter			9		3		9.70%
Chocolate Malt			5		350		5.40%
Crystal 80			4		80		4.30%
Caramunich III			2		78		2.30%
Caramunich II			1		56		1.00%
Water Profile	ppm
Bru'n Water Brown Malty (modified)
PH: 5.4
Calcium	50
Magnesium	5
Sodium	16
Sulfate	21
Chloride	62
Bicarbonate	88
Water Additions					Mash		Sparge
Gypsum
Epsom Salt					0.3g		0.4g
Canning Salt					0.3g		0.4g
Baking Soda
Calcium Chloride					0.5g		0.5g
Chalk					0.5g
Pickling Lime
Lactic Acid
Mash Schedule	Step Temp.				Step Time
Single Infusion Batch Sparge
Mash volume: 6.88qt
Sparge volume: 1.82 gal
Infuse 6.88 qt at 167F	152				60
Sparge 1.82 gal at 180F	180
Boil Schedule	Volume		Unit		Time		IBU
60 minute boil
Cascade	0.75		oz		60		36
Table sugar	4		oz		10		0
Fermentation Schedule	# Days		Temp.
Yeast: INIS-711 German Monk Lager
Starter: 2.5 liter
Pitch at 52F	20		52
Cold crash 32F	5		32
Freeze concentrate
Further aging?
Package at 2.2 vol

Brewday Notes

Brewed 1.17.2021.

First runnings: 1.075

Preboil gravity: 1.057

Preboil volume: 3.1 gal

Mash efficiency: 83%

Postboil gravity: 1.075

Postboil volume: 2.4 gal

Brewhouse efficiency: 86%

This beer enjoyed a long four month slumber at ambient temperatures following a three week fermentation at lager temperatures. I didn't intend to let the beer sit that long but I didn't have quite enough room in the chest freezer until the end of April. 

Once I had space for the beer I racked it into an empty 2.5 gallon water jug. I filled a little less than two gallons to give the beer room to expand as it froze but it ended up rupturing anyway and leaked a few ounces into the freezer. I left it in the freezer for five days--not because it needed that long but because I didn't get back to it during the workweek. I pulled it out and propped it up to drain its alcoholic contents into a jug for continued aging.

It's tipped on its side rather than set up to drain from the spigot on the plastic jug so the point of rupture won't leak out at the same time. I cut the hole larger and poked some air holes to let the concentrated beer drip. 

The block of ice is a huge solid mass but there is a small amount of free liquid in the bottom slowly dripping out. As it slowly thawed overnight the drips accelerated but it took approximately ten hours to procure a gallon of concentrated doppelbock back out of the ice. (The ice itself took almost two days to fully thaw in the sink.) I was awoken at four in the morning to a loud crash as the ice block shifted inside the jug and the wet exterior slid the whole thing off to the floor. 

I tasted the early drippings (runnings?) of the doppelbock which were alcohol hot, acidic and salty. I recall the same characteristics the last time I tried freeze concentrating more than a decade ago. The last runnings were still hot but no longer salty and acidic. I'm not sure if the salt and other minerals in the beer concentrate as the water freezes or what physical process explains that but the taste is salty and not mineral-y. 

The final drippings of the eisbock continued to taste hot with alcohol and almost overwhelmingly intense caramel malt flavors although not as sweet as I would have expected. It feels like it needs sweetness to balance but that may calm with time. I plan to let it mellow for a few months before revisiting. I may add oaked whisky at packaging to add sweetness to the beer if it seems to need help. Bourbon has similar flavors but a lot of sweetness so it would be a good faux barrel aging effort to bring balance to the beer. 

Ice Beer Tasting Notes

Appearance: Pours brownie dark brown with a thick dark tan head. The head is rocky and mousse-like that lingers through the beer although not creating much lacing. Although mostly opaque it isn't cloudy or hazy. 

Aroma: Caramel, dark roast coffee, milk chocolate, hint of smoke.

Flavor: The beer starts off with a burnt caramel flavor with espresso, lighter caramel, cocoa and milk duds. There is a sharp roast note to it that makes the beer taste closer to a 2000s imperial stout than a doppelbock but not quite as roasty. In the back end there is a plastic/rubber taste that sometimes is so unnoticeable that it disappears but in the next sip appears and ruins the end of the pour. It tastes almost freezer burnt. No hop flavor. No alcohol burn. 

Mouthfeel: The mouthfeel is thick and stout-like and the mousse-like head gives it a creamy texture that really sells a stout-like experience. It is smoother than an imperial stout and slides away without any roughness or acidity. It carbonated nicely and the carbonation feels right around the low two volumes of CO2.

Overall: The rubber note ruins the experience. The beer is not exceptional otherwise but a solid attempt if not for the plastic/rubber. I am not entirely sure if the rubber off-flavor is something the beer picked up from the plastic container but that doesn't make tremendous sense because it is designed for fluid storage. Maybe freezing the container released some of the plasticizers? Maybe all the hot side plastic in my brewhouse normally drops these flavors but without concentration it falls below the flavor threshold. Either way I don't like the rubber flavor enough to power through the remaining twelve bottles. 

Otherwise I would consider rebrewing this beer as is with the exception of perhaps dialing down the chocolate malt. While the flavor was interesting it was a touch too sharply roasty at the very front. The chocolate malt is the probable culprit. 

If I had to guess I would say this probably clocked in around 13-14% ABV by its feel. It didn't taste or feel boozy and quite the opposite it felt deceptively smooth until I got through about half the glass and realized I was starting to feel it.