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Brewing high gravity beers with sugar

In our series on brewing Belgian styles we already mentioned that many Belgian strong ales typically use sugar (sometimes up to 20%) as part of their fermentables. But sugar is not used only in Belgian ales. Granted, these ales are most famous for their use of sugar, but other strong ales, especially English, Scottish and French strong ales, also traditionally use a certain amount of sugar, and recently American brewers have begun to use sugars as part of the increasingly popular strong American IPAs.

Surprisingly, strong ales are not the only beers to be brewed with sugar. What many people don't realize is that In some countries (including South Africa) mass-produced industrial lagers also contain a significant amount of sugar to lower the cost of production. However, in this case the sugar is listed on the label as "Maize". This is essentially a legal loop hole, because the sugar used in these beers is glucose syrup (also known as corn syrup) which is produced from maize. In fact, one of South Africa's leading lager brands is brewed with about 60% of malt, the rest is glucose syrup, while the most recent entry on the South African local lager market only contains about 40% of malt (!) and the rest is glucose.

Sugar advantages

Brewing with sugar has several advantages. In Belgian ales, the main reason for the use of sugar (sometimes up to 20%) is that sugar will ferment out completely, which will increase the attenuation of the beer and lower the final gravity. This is important, because a high finishing gravity makes for a very satiating beer that can make the drinker feel full and bloated. As a general rule, the lower the finishing gravity of a beer, the more drinkable the beer will be. The amount of sugar in Belgian ales tends to be larger than in other styles, and Belgian yeasts are known for their ability to ferment sucrose (table sugar) without producing cidery off-flavours.

In traditional English, Scottish and French strong ales the sugar is usually a darker variety because these beers are, by and large, dark ales. The use of dark sugar can add warmth, complexity and character to these beers. Molasses, golden or dark syrup and hone may also be used in these ales. These strong dark ales can contain up to 10% or so of sugars.

In mass produced lagers the main reason for the use of maize-derived glucose is cost reduction. In industrial quantities the cost of glucose syrup as a source of fermentable sugars is lower than that of malt, and all the brewery has to do is to add a pinch of black malt to give the beer a little colour.

The use of sugar can also make life easier for the brewer because, unlike brewing grains, sugars do not need to be mashed and boiled. This means they can be added to the beer at any time: at the start of the boil, halfway through or at the end of the boil, and even post-boil during fermentation. All these options have their advantages and disadvantages.

Early sugar addition

During the boil Maillard reactions darken the wort. This is commonly known as "kettle caramelization", which is a misnomer because sugars only caramelize at temperatures far above the boiling point of wort. How much the wort darkens depends on several factors, one of which is wort gravity. High gravity worts darken more during the boil than low gravity worts do. This means that when you add your sugars to the wort at the start of the boil (known as an early sugar addition) the wort will darken more due to the higher gravity. The heat of the boil also promotes the formation of more complex flavours.

A major advantage of adding the sugar early in the boil is that the combination of heat and the acidity of the wort will cause the sugar to invert. This means that sucrose (a disaccharide) is converted into glucose and fructose (both monosaccharides). Because many yeasts do not like sucrose and tend to produce cidery off-flavours in the presence of significant levels of sucrose, early sugar additions are the way to avoid this. The wort darkening and added complexity makes this method especially suitable for brewing dark, strong English, Scottish and French styles.

The greatest disadvantage of adding sugar early in the boil is that the hop utilization will suffer. The higher the wort gravity, the less bitterness will be extracted, and the more hops will be needed.

Late sugar addition

This is a popular method when brewing strong Belgian ales. Adding the sugar at the end of the boil (at flameout) allows the sugars to dissolve into the hot wort easily, but no wort darkening takes place. This is absolutely vital when brewing the famous strong blonde and golden Belgian styles (Duvel is a good example) and while a Tripel can be deep gold, too much darkening is undesirable. Also, with a wort gravity typically in the high 1.080s or the 1.090s, hop utilization becomes a major factor when it comes to production cost. Having a lower boil gravity improves the hop utilization and reduces the amount of hops required.

The disadvantage is that the sugar will not be inverted (at least not to any appreciable degree). Sucrose will remain sucrose, which means that this method is only suitable for beers fermented with proper Belgian strains that can handle significant levels of sucrose without producing off-flavours. it is generally not recommended in beers fermented with regular types of yeast. However, many factors come into play here, including the percentage of sucrose, the type, amount and health of the yeast, the amount of oxygen the yeast has to work with, the total wort gravity and several others. So your mileage may vary and experimentation is the best way to find out what you can get away with. One way to get around this disadvantage is not to use sucrose (table sugar) but a monosaccharide such as dextrose or glucose.

Post-boil sugar addition (a.k.a. staggered fermentation)

This option involves a sugar addition several days into the fermentation, typically at the point where the beer is halfway through the expected attenuation, or three days or so into the fermentation. This is also known as a "staggered fermentation". There are several main advantages to be had here.

First of all, the yeast will not have to deal with a very high starting gravity. This means you will need to pitch less yeast. Also, because the yeast will start the fermentation on a diet of familar malt sugars rather than sucrose or other refined sugars, the stress on the yeast will be reduced.

Secondly, the fermentation will be easier to control. Unleashing your yeast into a wort practically crystallizing with fermentable sugars can result in a very vigorous, not to say volcanic, fermentation. The heat produced by a vigorous fermentation can also spike the wort temperature. This in turn speeds up the fermentation and the generation of heat even more, to the point where things can easily get out of hand. Starting with a lower wort gravity, giving the yeast a few days to reduce the gravity and then raising it back up by adding the sugars is a good way to help keep things under control.

Thirdly, the production of esters and fusel alcohols during fermentation is, among other things, a factor of wort gravity. All other things being equal, the higher the wort gravity, the higher the levels of fruity esters and fusels. In high gravity beers, especially when fermented with estery yeast strains, ester levels can easily climb to the point where they become overpowering, especially if the wort temperature spikes due to an overly vigorous fermentation. Keeping the gravity down helps to control the levels of fruity esters.

Adding sugar to the fermenter rather than to the wort kettle also means that none of these fermentable sugars will be lost in the kettle trub.

Another possible advantage of adding sugars halfway through the fermentation depends on the yeast. Some yeast strains are somewhat lazy, and prefer to digest sucrose and simple sugars rather than malt sugars such as maltose and maltotriose. In the presence of high levels of refined sugars they change their metabolism to deal with the refined sugars and may loose their ability to ferment malt sugars in the process, which in turn results in a stuck fermentation. Whether or not this may happen depends on a number of factors, but the most important parameters here are the level and type of sugar used and the yeast strain. Adding the sugars to the fermenter after the yeast has already gone through most (or even all) of the malt sugars will prevent a stuck fermentation as a result of yeast "sugar shock". Reports from the field also indicate that many Belgian yeasts tend to ferment the beer a few gravity points further down when sugar is added during the course of the fermentation.

Sugar can be added to the fermenter all at once, or in increments. Which option to use is a matter of preference, and also subject to factors such as the amount of sugar used and the gravity of the beer. Large amounts of sugar are reason to consider incremental additions. Sugar additions halfway nto the fermentation are traditionally used in Belgian brewing, but there is no reason why it wouldn't work elsewhere. Just keep in mind that if you do not use a Belgian strain the use of dextrose or glucose instead of sucrose may be necessary to prevent cidery flavours. When you add the sugar to the fermenter be careful not to disturb the Krausen too much, not to introduce more air into the wort than is unavoidable, and to reduce the risk of infection to a minimum.

When is the best time to add the sugar to the fermenter? This is largely a matter of opinion, which suggests that it might be a factor of wort gravity, beer style, yeast and what not. Your mileage may vary. Typical addition schedules start at 24 to 48 hours after the start of fermentation, and involve one, two or three sugar additions with 24 hour intervals between subsequent additions.


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