Q. My wife gave me a dehydrator that I have been drying all sorts of fruits with. I have developed a beer recipe using dried citrus that has been a big hit. Now I want to know more about using dried stone fruits in beer and the pros and cons of dry vs. fresh.
Frank Korn 
Connecticut

Mr. Wizard Says …

I love the idea of using your new food dehydrator to preserve fruit for brewing. There is nothing wrong with using dehydrated fruit in beer; however, its flavor and color contributions will differ from those of fresh fruit. To answer your question, I’ll begin with fresh fruit and then discuss various preserved fruit products, highlighting how they compare with their fresh counterparts.

Brewers have many options when it comes to selecting fruit for brewing. Common choices include blackberries, raspberries, strawberries, grapes, papayas, oranges, lemons, apples, pears, apricots, peaches, cherries, mangoes, pineapples, and figs. These fruits can be grouped into several general categories, as shown in the table below.

Aggregate fruits are among the easiest to use in brewing because they can be added directly to beer with little or no processing. Their colors, sugars, and acids readily diffuse into beer as the soft cellular structure breaks down due to naturally occurring fruit enzymes. The same process occurs when these fruits are stored for extended periods.

Stone fruits also break down readily in beer, but because of their larger size they are often cut into smaller pieces after removing the pit. 

Apples and pears are almost always juiced because their juice is trapped within a pectin-rich cellular structure that requires grinding or milling for efficient extraction. Pineapples and figs present a different challenge because their proteolytic enzymes can negatively affect beer foam stability if the fruit has not been pasteurized.

Fresh fruit can also be troublesome because it commonly carries a diverse population of microorganisms ranging from useful and interesting yeasts to spoilage yeasts and bacteria. Despite these risks, fresh fruit contributes vibrant aromas, fermentable sugars, bright colors, and crisp acidity. For many brewers, the benefits outweigh the drawbacks, and fresh fruit is used before, during, or after fermentation.

In commercial brewing, the risk posed by wild yeast and bacteria is a major concern for most beer styles outside of intentionally mixed-culture or wild-fermented beers. Aseptic processing is widely used in the juice industry because it preserves much of the fresh character of juice while eliminating spoilage organisms. Process details aside, aseptic juices are typically single-strength, pasteurized, shelf-stable versions of their fresh counterparts and can be difficult to distinguish from freshly prepared juice.

Although aseptic processing sounds simple — juice, heat, cool, and package — the details are critical. For readers interested in learning more, this Oregon State University Extension article provides an excellent overview. The advantages of aseptic juices are that they are widely available, easy to use, microbiologically stable, and often reasonably priced.

No discussion of fruit products would be complete without briefly mentioning canned fruit preparations. These products are an option, but canning is more commonly used for concentrated juices, pie fillings, jams, and preserves. Because of the relatively intense heat treatment used during production, cooked or jam-like flavors are common. Although not widely used, these products occasionally appear in homebrewing recipes.

And then there are dried fruits.

When I think of dried fruit in brewing, the first example that comes to mind is dried orange peel in witbier. Dried herbs and spices, while not fruits, fit into a similar category of flavoring ingredients. Witbier typically contains dried coriander seed and may also include dried orange or lemon peel, chamomile, grains of paradise, pepper, ginger, lemongrass, or cardamom. Dried citrus peel contributes a rounded, full, and slightly candied flavor profile that differs markedly from the bright, zesty, and explosive character of fresh citrus peel.

Why the difference?

When fruit is dehydrated, sugars, proteins, acids, and other flavor-active compounds become concentrated. The application of heat promotes a variety of chemical reactions that alter flavor and color. Oxidation reactions change pigment composition, promote polyphenol polymerization, and transform fresh, bright flavors into richer, more rounded flavors. These changes should not be viewed as inherently good or bad; they are simply natural consequences of the drying process.

The type of fruit also matters. Pome fruits, such as apples and pears, become leathery when dried, making them ideal hiking snacks but less ideal brewing ingredients because they do not readily rehydrate. Nevertheless, all fruit types can be dried and successfully used in brewing.

In the brewer’s toolbox, dried fruits offer a unique range of flavors that bridge the gap between fruit and malt. Their concentrated, oxidative character can echo the flavors found in specialty malts while complementing malt richness, alcohol warmth, and fermentation-derived esters in many beer styles.

In short, I see many advantages to using your new gadget for brewing. As someone who enjoys malt-forward beers, I find it easy to imagine dried stone-fruit flavors pairing beautifully with caramel malts, Vienna and Munich malts, honey malt, and worts produced using extended boil times.

Before concluding, I want to revisit fruit processing and discuss one thing dehydration does not necessarily accomplish: Microbial kill.

Although dehydration is extremely effective at preventing microbial growth by reducing water activity, it does not reliably kill microorganisms. While microbial populations generally decline during drying, especially when heat is involved, the surfaces of dried fruits often remain populated with viable yeast and bacteria.

Two common methods used to reduce these microbial populations are sulfur treatment and pasteurization. Sulfur dioxide, produced by burning elemental sulfur, can be applied during drying as an antimicrobial treatment. This same approach has long been used to sanitize wooden barrels before being stored dry. A related method involves dipping fruit in a potassium metabisulfite solution before dehydration. Both treatments suppress yeast and spoilage bacteria while helping preserve fruit color.

Steam pasteurization is another effective option. At first glance, using steam on dried fruit may seem counterintuitive because the goal of drying is to remove water. However, steam is a highly effective sanitizing medium because moist heat transfers energy more efficiently than dry heat, and condensing steam delivers substantial thermal energy to microbial cells. In practice, dried fruit can be steam pasteurized near the end of the drying process, and the residual heat in the fruit helps remove surface moisture so that the treatment causes only a minimal increase in overall moisture content.

These treatments significantly reduce microbial populations, but they do not guarantee sterility. Fortunately, spoilage bacteria are generally easier to kill than yeast, and the relatively low populations of surviving wild yeast usually have little impact when fruit is added to finished beer. When fruit is added during active fermentation, the brewing yeast will generally out-compete any remaining wild microorganisms.