Brewing Light Lagers
Q: In preparation for spring I want to come up with a good plan to brew a light lager beer. When I say light, I mean lower in calories and alcohol than the average 5% beer. Do you have any suggestions that will help me?
— Mike Brown
A: Brewing light lagers that have very subtle flavors atop a stark white canvas is difficult. Little flaws in the recipe balance and off-flavors easily masked by bigger beers stick out like a fleck of pepper in a bowl of milk. There are a few basic tips that will help get you started and the first concerns water. The best thing to do for this style is buy reverse osmosis water from a local grocery store and add water salts to produce water with about 50 mg/L of calcium. I prefer to use calcium chloride for this type of beer because chloride has a softer effect on flavor than sulfate. If you use calcium chloride and add 0.02 ounces per gallon (0.14 g/L) of mineral free water you will have the 50 mg/L of calcium I suggest.
The next ingredient you need to select is malt. If you are not an all-grain brewer, consider delaying this brew until you begin brewing using mashing as part of your routine. The type of malt you select is really up to you. Clearly pale-colored malt is required, but you have a pretty wide selection of pale lager malts to choose amongst. If you plan on using adjuncts you may want to use some 6-row malt in your grist bill, but many of today’s 2-row malts produced from North American barley have enough enzymes to handle up to 15–20% adjunct with little problem. Light beer is not the style to start adding a bunch of special malts, but if you do want just a little color and malt flavor a dash of higher kilned pale malt, such as 10 °L Munich malt, or crystal malt can be used. Just don’t get carried away with these ingredients because a little bit goes a long way.
Next is the most critical process to consider; mashing. The underlying principle to light beer brewing is the production of wort that is highly fermentable and there are two ways to achieve this goal. The easiest on paper is to add exogenous enzymes (enzymes from sources other than malt) to the mash. The best way to produce very fermentable wort, however, is by controlling the mash. Not only is this relatively easy, but it works very well. The main difference, however, is that extended mashes do not hydrolyze all of the malt starch into fermentable sugars so there is residual carbohydrate in beers using extended mashing. For this style of beer you want to have a wort gravity somewhere between 8–9 °Plato or 1.032–1.036.
The type of mash you need to use is a multi-temperature step mash. I suggest beginning your mash at about 122 °F (50 °C). This first step is used by some brewers to encourage proteolytic activity, but for this style it is just a good starting point to get your water and malt properly mixed together. A good ratio of water to malt for this style is about 3.5 parts water to 1 part malt by weight (3.5 liters water per kilogram malt or 0.42 gallons per pound). Hold the mash at your mash-in temperature for about 15 minutes and begin heating toward a target of 145 °F (63 °C). It is absolutely vital to this type of beer not to over-shoot the target temperature. A useful technique is to shut off the heating when you get to about 140 °F (60 °C) and let the mash temperature settle. Then slowly heat up to 145 °F (63 °C). Why is this so critical? Well the whole purpose of this method is to hit a temperature where both beta and alpha amylases are happy and to hold this temperature for at least two hours . . . that’s right, two hours minimum! If you want to go longer you can, but at some point the rate of change in an enzymatic reaction approaches zero as the concentration of substrate approaches zero.
This is all very easy for me to explain, but the execution is not easy because the mash cools off fairly quickly. In a commercial brewery things are controlled automatically and as the mash cools the heating jackets and mash agitator kick on and off to keep the mash temperature within a defined control range. You are going to have to do the same thing at home by carefully monitoring the mash. I think two to two and a half hours is a reasonable time to fuss over the mash.
After the long hold at 145 °F (63 °C) is over you need to heat the mash up to about 158 °F (70 °C) so that alpha amylase can reduce the size of any large starch molecules that may have survived. After a brief 10–15 minute hold, mash off at 168 °F (76 °C) and transfer to the lauter tun.
Things are pretty standard from here on out; boil for 60–90 minutes and use a modest hopping rate during the boil to target around 10–20 IBUs, depending on your personal preferences. Cool the wort down to around 50–55 °F (10–13 °C), aerate well and pitch a clean-fermenting lager yeast strain. If you pitch at a proper level (about 10–15 million cells per milliliter of wort) primary fermentation should be complete in seven to ten days. Carefully rack to your secondary and store as close to 32 °F (0 °C) as possible for about 3-4 weeks to allow the beer to naturally clear.
