Bottles of skunked or expired beer can be used in recipes, if you follow a couple crucial rules. Brianna Soukup/Staff Photographer

I have the best friends. Really, I do. One even brought me a cooler of skunked beer.

He’d recently found it in the basement of his cottage in West Bath, but could not recall at which party or during which summer he’d originally offered up the beverages – Yuengling lager, Corona Lights, Dark Toad dark ales and a nonalcoholic variety whose label had disintegrated in the melted ice still slushing around in the orange insulated cooler.

If anyone could conjure up a culinary use for skunked beer, his money was on me, he said. Always up for a challenge, I researched the possibilities.

Christine Burns Rudalevige pours a cup of skunked beer into chocolate cake batter. Brianna Soukup/Staff Photographer

Probably the most important thing I learned from the dozen or so Maine craft brewers I tapped for information was that beer doesn’t get skunked the way I’d always thought it did. Although most of my college beer came from kegs, we’d occasionally treat ourselves to high-class Rolling Rocks in green bottles. We took care to keep them cold, as we were warned that if they become warm and we tried to cool them again, they’d likely pick up a wet cardboard taste and musty smell that even broke college kids can detect.

But I got bad information about how beer goes bad, these brewers said. Skunking is not caused by moderate changes in temperature, but when the hop-derived molecules in the beer are exposed to ultraviolet light. “Best way to skunk a beer is to get the juiciest, hoppiest IPA, put it in a clear glass and set it outside in sunlight for 10 minutes. It light-strikes the beer, and thus ‘skunks’ it,” said Matthea Daughtry, co-owner of Moderation Brewery in Brunswick.

Local brewers say they avoid light-struck beer by keeping it in the keg until it flows through a tap in their tasting room or package it in cans or dark glass bottles to protect it from damaging UV rays. But still, it can happen to any beer under the right conditions.

The internet tells me that light-struck beer is still good for all of beer’s nonculinary uses. Put a bit in a bowl a few feet away from the picnic table to keep the bees occupied while you enjoy your meal, for example. Or use it to attract and drown pesky garden slugs. You can rub some into your dull wooden table to revive its luster, rinse your hair with it to bring out the natural highlights, or soak your feet in it so the yeast will help soften the skin and the carbonation will exfoliate it.

But can you cook with it? You can, if you follow two basic rules. Don’t use it in any recipe where the liquid is going to be reduced, because the process will make the musty flavor more prevalent. You can, for example, use it to quickly steam bratwurst, but adding skunked beer to a long-simmering stew will concentrate its off flavor. The second rule is to be conscious of how a musty flavor works with other ingredients in the recipe. Pair it with the roasted flavors of coffee, chocolate or peanuts; dampen its earthy tone with spices like cinnamon, cloves and nutmeg; and add a counterpoint with something tangy, like the sauerkraut in this cake and its cream-cheese frosting.

CHRISTINE BURNS RUDALEVIGE is a food writer, recipe developer and tester and cooking teacher in Brunswick, and the author of “Green Plate Special,” a cookbook from Islandport based on these columns. She can be contacted at cburns1227@gmail.com.

Christine Burns Rudalevige frosts a chocolate cake that was made using skunked beer. Her college-student neighbors couldn’t taste a difference between it and one made with fresh beer. Brianna Soukup/Staff Photographer

Beer-Sauerkraut Chocolate Cake

This is not a cake that needs to be made with skunked beer. But it certainly can be. I tested this cake with both skunked beer and fresh beer and served both to the 12 college students who live next door. They could not tell the difference. They just declared it an excellent cake.

Makes one 9-inch layer cake

For the cake

1/2 cup (113g) unsalted butter, softened, plus extra for preparing pans

1/2 cup (46g) Dutch-processed cocoa powder, plus more for preparing pans

2 cups (240g) all-purpose flour

1/2 teaspoon cinnamon

1 1/2 cups (300g) sugar

1 teaspoon vanilla extract

1 teaspoon baking soda

1 teaspoon baking powder

1/2 teaspoon salt

3 eggs

1 cup beer

3/4 cup fresh drained and very finely chopped sauerkraut

For the frosting

3 1/2 cups (440g) confectioners sugar

1/2 cup (46g) Dutch-processed cocoa powder

4 ounces (113g) unsalted butter, softened

8 oz (226g) cream cheese, softened

1 teaspoon vanilla extract

1/4 teaspoon salt

Preheat oven to 350 degrees F. Butter the bottom and sides of two 9-inch layer cake pans. Dust each pan with a scant teaspoon of cocoa powder.

To make the cake, in a medium bowl, sift cocoa powder, flour and cinnamon together and set aside. In a large bowl, use an electric mixer to cream butter, sugar, vanilla, baking soda, baking powder and salt together until fluffy, about 3 minutes. Beat in eggs, one at a time. Alternate adding cocoa-flour mixture and beer to the batter, beating for 30 seconds after each addition. Add sauerkraut and beat for 30 seconds.

Pour batter into greased pans. Bake 20-23 minutes until a toothpick inserted into the center of the cake comes out clean. Cool cakes in their pans for 10 minutes. Turn the cakes out onto wire racks to cool completely.

To make the frosting, in a medium bowl, whisk together sugar and cocoa powder. In a large bowl, combine butter and cream cheese and use an electric mixer to beat until creamy, well-combined, and lump-free, about 2 minutes. Add vanilla and salt and mix for 30 seconds.

With mixer on low, gradually add sugar-cocoa mixture, taking time to scrape down the sides of the bowl about every 30 seconds. After the last addition, beat frosting for 1 minute. Frost cooled cake.