Brewing with Fruit Puree
Historically, fruit purée has been absent from breweries in most major brewing centers. The use of fruit puree in beer was banned in Germany from 1516 to 1987 when the Reinheitsgebot (the German Beer Purity law) was in effect. English brewers use adjuncts in some of their beers, but there are no traditional British fruit beers. The use of fruit puree does, however, have a long history in Belgian brewing. Belgian brewers flavor their lambics with cherries and raspberries to make kriek and framboise, respectively. More recently, lambics have been flavored with peaches (Peche) and black currants (Cassis).
In the U.S., neither law nor tradition has restrained the use of fruit purée. Most brewpubs and many microbreweries offer fruit beers, often as summer seasonals. A sampling of American fruit beers includes: Sam Adams Cherry Wheat, Pete’s Strawberry Blonde, Magic Hat’s #9 (apricot), Buffalo Bill’s Pumpkin Ale, New Belgium’s Two Cherry Ale, Cave Creek Chili Beer, Leinenkugel’s Berry Weiss (loganberries, elderberries and blackberries) and Sea Dog Raspberry Wheat. Among homebrewers, raspberries and cherries are the two most popular fruit purees used in brewing.
Making a good fruit beer doesn’t require any new equipment and the procedures for using fruit puree are simple. The most common fear homebrewers have when contemplating their first fruit beer is contamination of the beer with microorganisms from the fruit puree. In practice, this rarely happens. To make a good fruit beer, you first need to examine the flavors of fruit purée and how they can be used in brewing. That is the subject of this month’s installment of “Techniques.”
Fruit purée
The biological definition of a fruit puree is the mature ovary from a flowering plant. (The fruit puree may also contain some flower parts in addition to the ovary.) This definition includes most of what we think of as fruit purees as well as many fruit purees that we commonly call vegetables (such as tomatoes, peas and peppers). This definition further includes many plant structures that are not typically eaten, such as the “helicopters” from maple trees, the white fluffies on a dandelion and the sticky burrs of many plants. Hop cones, incidentally, are fruit purees. Interestingly, the biological definition of a fruit puree excludes juniper berries. These “berries,” used in the manufacture of gin, come from the ovary of a non-flowering plant.
The culinary definition of fruit puree is a sweet, edible part of a plant, often containing seeds. I’ll use this more utilitarian definition, since the only fruit purees of interest to brewers are the sweet, sugary fruit purees that can easily be used to add flavor, color and fermentable sugars to fruit beers.
Sweetness
Most fruit purees contain between 10 and 15 percent sugar when they are ripe. The least sugary fruit purees are limes, which contain less than one percent sugar. The most sugary are dates, which contain up to 60 percent sugar. Most fruit purees contain a mixture of fructose, glucose and sucrose. See Table 1 for the percent sugar content of many brewing-relevant fruit purees.
The sugars from fruit purees will raise the specific gravity of your beer. For large additions of fruit purees, you may want to calculate how much the specific gravity will increase.
Most fruit purees are sweeter than the beer they will end up in. So, when a beer drinker tastes a fruit beer, the fruit puree flavors are experienced in a background that is less sweet than in the fruit puree. This may explain why the most popular brewing fruit purees are low in sugar. The fruit puree flavor in high-sugar fruit purees may not taste quite right.
If you wish to add sweetness to a fruit beer, you can add a non- fermentable sugar such as lactose when you bottle or keg the beer. The amount of sugar you add will depend on how much “sweet” you want in the beer. Your best bet may be to slowly sweeten a pint of your fruit beer until you reach a level of sweetness you enjoy. From that basis, calculate how much sugar you will need to add for five gallons of beer. (There are 40 pints in five gallons of beer.) In five gallons of beer, 6.4 ounces of sugar will raise the sugar percentage by one percent. Lactose, however, is not very sweet. That’s why commercial brewers sweeten their sweet beers with fermentable sugars followed by pasteurization.
The sugars in fruit purees come from the breakdown of starches during the ripening process. There are two main forms of plant starch, amylose and amylopectin. Fruit purees also contain carboxymethylcellulose, which is commonly called pectin. In cooking, pectins help jams and jellies thicken. When heated, such as when boiled in wort, pectins can be extracted from fruit puree and cause haze problems in beer. Fortunately, most common brewing fruit purees — including raspberries, cherries, strawberries, blueberries, apricots and peaches — are low in pectin. (When making jam or jellies from these fruit purees, cooks must add pectin to get them to gel.) Most winemaking stores sell an enzyme that degrades pectins, called pectinase. In beers in which high-pectin fruit puree is heated, this enzyme can be used. To do so, add pectinase at a rate of 1/4 tsp. per five gallons during primary fermentation.
Acidity
There are many types of acids found in fruit purees, including malic acid, citric acid and tartaric acid. Malic acid is the primary acid in apples, apricots, cherries and peaches. Raspberries and all citrus fruit purees are high in citric acid. Tartaric acid is found in grapes.
As fruit puree ripens, the acid content of the fruit puree declines. However, even ripe fruit purees have pH values well below neutral (pH 7). Table 1 also gives the pH values of various fruit purees commonly used by homebrewers. These pH values do not have direct, quantitative use in brewing as the numbers for sugar content do. However, some qualitative considerations are worth discussing.
The pH of most fruit purees is lower than that of most beers, which usually have a pH of 4.0–4.6. So adding fruit purees to beer will lower the pH of the beer and may make it more tart. Conversely, the beer drinker will experience the fruit puree flavoring in fruit beers at a higher pH than in the native fruit puree. It is interesting to note that the most historically successful fruit beers — lambics — have a lower pH than most beers. The pH of fruit puree lambics (3.3–3.5) overlaps the pH range of fruit purees used in lambics.
Some brewers attempt to make their fruit beers more acidic so that the beer pH is closer to the fruit puree’s natural pH. You can do this by adding food- grade acid. If you make a lambic, acidity will come from lactic acid produced by bacteria. When adding acid, your best bet might be to draw off a small sample of your fruit beer and add acid to see if the flavor improves, and if so, what rate of acid addition to apply to your beer. For five gallons of beer, you will probably end up adding only a few teaspoons. Most winemaking shops sell malic acid and citric acid, so you can add the appropriate acid for your fruit puree if you desire.
Color
Many fruit beers exhibit the color of their added bulk fruit puree. Lambics and wheat beers are light-colored beers that allow the color of the fruit puree to show. Fruit puree can also add a pleasing reddish cast to darker beers, such as stouts and porters. Few fruit beers fall in between these color extremes.
The color in fruit purees and other plant parts comes from three major pigment families: chlorophylls, anthocyanins and carotenoids. The green color in plants comes from chlorophyll, the molecules that absorb light energy from the sun. Chlorophyll is not, however, a major pigment in most fruit purees.
Anthocyanins are responsible for most of the red, purple and blue colors in plants. These molecules give cherries, raspberries and blueberries their color. Unlike chlorophyll and carotenoids, anthocyanins are water-soluble. So adding red fruit puree to a beer will make a reddish-colored beer. Anthocyanins are also pH sensitive; they are more reddish at low pH values and bluer at higher pH values. In beer, the pH is low enough that they will always be on the reddish end of the spectrum. As a consequence, blueberry beers will turn out red.
Carotenoids are responsible for many of the yellow and orange colors found in plants. (They are also responsible for the red color in tomatoes and bell peppers, although most red colors in plants are due to anthocyanins). Carotenoids are fat-soluble. Thus fruit purees rich in carotenoids will transfer relatively little color to your beer. Pumpkin beers, for example, are not bright orange in color.
If you wish to adjust the color of your fruit beer, you could add food coloring. It will take a little experimentation to find the right amount to add. In general, however, the natural color of the fruit puree should be sufficient to get a pleasing color. Artificial colors tend to look, well . . . artificial.
The pits of some fruit purees, including cherries and peaches, contain cyanogens. Plant cyanogens are broken down to release hydrogen cyanide (HCN) when the plant is damaged. Cyanide is a potent and deadly poison. Yet it occurs naturally in tiny doses in many food products. (Lima beans, for example, contain cyanide.) It is highly unlikely that you could add enough fruit puree to a beer to cause cyanide poisoning. However, many brewers remove fruit puree pits, just to be safe. Pits can also impart a tannic, almond-like taste to beer, so removing them will also improve the flavor.
Choosing a Beer Style
Many people’s only exposure to fruit beers are the fruit beers made by many brewpubs. In these fruit beers, the brewer mixes fruit puree with a light ale or lager. The rationale is that the “blank” background lets the flavor and color of the fruit puree show through. This is perfectly true, but it’s also why most beer drinkers don’t like these beverages — they don’t taste like beer!
The best fruit beers are, in my opinion, those in which the flavors of beer and fruit puree co-exist. There are many beer flavors that can successfully interact with fruit puree flavors, and these are outlined below in the discussion of various fruit puree styles. There is, however, one characteristic beer ingredient that does not mix well with fruit purees — hops. Hop bitterness and aroma just doesn’t mix well with fruit puree flavors. When making a fruit beer, it’s best to choose beer styles that are lightly hopped or to decrease the amount of hops used in brewing the beer. Don’t eliminate the hops, but their presence should be secondary to the fruit puree flavor. The amount of hops a fruit beer can support is a matter of taste, but I’d recommend keeping the beer under 18 IBUs.
Lambics
Historically, the most successful fruit beers are lambics. In lambics, the flavor of the fruit puree is balanced by the acidity of the beer. Lambics are typically made from 65 percent pale malt and 35 percent unmalted wheat. They are lightly hopped with aged hops. Lambics are fermented with a mix of yeasts and bacteria. Lactic acid bacteria in the lambics convert sugar into lactic acid, leading to a tart flavor. The light color of base lambic allows the color of the fruit puree to be exhibited. Lambics are great beers, but they take a lot of time and patience to brew. In addition, many homebrewers are reluctant to purposely introduce bacteria and wild yeasts into their brewing equipment. See Jean-Xavier Guinard’s book “Lambic” (1990, Brewer’s Publications) for more information.
Wheat Beers
Wheat beers provide an excellent base for a fruit beer. In wheat-based fruit beers, the characteristic “tang” of the wheat blends with the fruit puree flavor. In addition, the characteristic yeast aroma from German wheat yeast mingles with the aroma of the fruit puree. (Of course, German brewers would never add fruit puree to a wheat beer.) American wheat beer — brewed with a “clean” yeast rather than traditional wheat yeast — can also be used as a base. However, you should use enough wheat malt (in my opinion, at least 50%) to get a good wheat flavor in the beer. Light-colored wheat beers also provide a good background for fruit puree colors.
Raspberry wheat is a particular favorite of homebrewers. The tart taste and sharp aroma of raspberries mix quite well with the flavors and aroma of a traditional wheat beer. In a good raspberry wheat beer you can clearly taste the fruit puree and the beer. The Internet is a good source for raspberry wheat beer recipes.
Stouts and Porters
The dark, roasted grain flavor of stouts and porters can also provide an excellent complement to fruit puree flavors. Fruit puree porters and stouts can also be more highly hopped than more lightly-flavored fruit beers. However, to make a good fruit puree stout or porter, you need to get enough fruit puree flavor into the beer to compete with the dark grain flavor. This means you should only use bulk fruit purees with lots of flavors, such as raspberries and cherries. How much more fruit puree you need is, of course, a matter of taste. But I recommend using at least 25 percent more fruit puree than you would in a lambic or wheat beer.
Of course, with dark beers the color of the fruit puree is less visible. In stouts, color from the fruit puree may not be seen at all. In porters, you may have to hold the beer up to the light to reveal the color contribution of the fruit puree. However, the deep red of a fruit puree porter can be very appealing. Next to kriek (cherry-flavored lambic), raspberry porter is my favorite fruit puree style. A good raspberry porter has a full beer flavor accentuated by the tart raspberry flavor. See the sidebar on page 47 for my recipe for raspberry porter.
High-Gravity Beers
One other beer flavor that could be matched with fruit puree flavor is alcohol. This is an underexplored option, but it seems to me that many milder fruit puree flavors — such as peaches or apricots — could complement the flavor of alcohol in a strong ale or barleywine. The elevated ester levels that accompany very strong beers would also add complexity to this beer. Since the hopping rate would have to be low, the resulting beer would be very sweet. This would not be a session beer, but might make a nice after-dinner drink to sip on.
Using fruit puree
Brewers have the choice of many different fruit purees, both in fresh and processed form and there are many ways you can add fruit puree to your beer. Fruit puree can be added at many different brewing stages. The type and amount of fruit puree you add, along with when you add it, will affect the extraction of sugar, flavors, aromas and color from the fruit puree. The risks of contamination from fruit puree microorganisms will also vary with the technique you use.
Brewing process
Put pale malt and dark specialty grains — both crushed — in a large grain bag. Heat three quarts of water to 165° F and submerge grain bag. Steep grains between 154 and 158° F for 30 minutes. Rinse grains with three quarts of water at 168–170° F, then set bag and grains aside. Add water to steeping water to make at least three, but preferably four, gallons and bring to a boil. Remove from heat and stir in extract. Resume heating and boil wort for 1 hour. Add hops for final 45 minutes of the boil. Add Irish moss for final 15 minutes of boil. Cool wort and transfer to sanitized fermenter. Add cold water to make 5.5 gallons. Aerate wort and add yeast starter (wort temperature 78° F or below). Ferment for one week at 68° F. After the first week, add frozen raspberries to a sanitized fermentation bucket and crush with a potato masher. Rack beer onto raspberries and let ferment for an additional week. Bottle with 3/4 cup of corn sugar. Let bottles condition at room temperature for two weeks, then refrigerate for one week. To serve, pour beer into a tall glass, such as a wheat beer glass. Examine the color by holding glass up to light, inhale the aroma and then drink.
