Crafting Fruit Beers: Fermentation Techniques

The short answer: add fruit once the most vigorous part of fermentation is over for the brightest flavour; boiling fruit dulls its aroma and can set a pectin haze. Use about 0.5–1 lb per gallon (60–120 g/L) for a noticeable fruit character and 1–2 lb per gallon (120–240 g/L) for fruit-forward beers. Frozen fruit and aseptic purées are easiest: freezing breaks the cell walls, and aseptic purée is sterile. Fruit adds sugar, so let fermentation finish completely before packaging, or bottles can gush.

When to add	Effect
Boil	Safest from infection; least fruit aroma; can set a pectin haze
Whirlpool, below about 170°F (77°C)	Pasteurizes the fruit without boiling it; some aroma still lost in fermentation
Early in primary	Active fermentation carries off some aroma
After high krausen or in secondary	Brightest, freshest fruit flavour
In the keg	Quickest; use purée or extract, keep it cold and drink it fresh

How much fruit to use

For a 5 gal (19 L) batch, 0.5–1 lb per gallon works out to about 2.5–5 lb (1.1–2.3 kg) of fruit, and 1–2 lb per gallon to 5–10 lb (2.3–4.5 kg). Where you land depends on the fruit and the beer: mild fruit needs more, and a dark or hoppy beer hides fruit that would shine in a light wheat beer.

Fruit	Strength in beer	Tips
Raspberry, blackberry	Strong	Start at the low end of the range
Passion fruit, mango	Strong	Purée is easiest; passion fruit goes a long way
Cherry	Medium	Tart cherries give more flavour than sweet ones; use purée or pitted fruit
Peach, apricot	Mild	Purée; top of the range
Strawberry, blueberry	Mild	Top of the range; the aroma fades quickly, so drink it fresh
Orange, lemon, grapefruit	Strong (zest)	Use the zest without the bitter white pith, late in the boil or in the whirlpool

How to add fruit to the fermenter

1. Let the main fermentation slow down. For most ales that’s after high krausen, usually three to five days in.
2. Prepare the fruit. Aseptic purée: sanitize the outside of the pouch or can and whatever opens it. Frozen fruit: thaw it in its sealed bag. Fresh fruit: wash it, remove stems and pits, then freeze it or pasteurize it (below). A dose of pectic enzyme with the fruit helps prevent haze.
3. Sanitize everything that touches it: funnel, mesh bag, port, gasket and clamp.
4. Add it and leave headspace. The fruit adds volume and the refermentation foams. Whole fruit goes in, and comes out, more easily in a sanitized mesh bag.
5. Hold the beer at its fermentation temperature. Expect fresh activity within a day or so. Refermentation makes heat like any fermentation, so leave your temperature control running.
6. Wait until it stops again, usually one to two weeks. When two gravity readings taken a few days apart match, cold crash and package.

Adding fruit to the primary saves a transfer, and every transfer is a chance to pick up oxygen. If you do rack onto fruit in a secondary, purge that vessel with CO₂ first.

Purée, whole fruit, juice or extract

Form	Good	Watch out for
Aseptic purée	Sterile, pourable, consistent	Fine pulp can clog valves and dip tubes
Frozen whole fruit	Freezing breaks the cells, so flavour comes out easily	Freezing doesn’t sanitize; bulky; stems and pits
Fresh whole fruit	Best aroma in season	Highest infection risk; freeze or pasteurize first
Juice or concentrate	Easy, no solids	Preservatives such as potassium sorbate or sodium benzoate stop yeast; concentrate can taste cooked
Extract	Dose to taste at packaging, no refermentation	Can taste artificial

Keeping it clean

Fermenting beer protects itself: alcohol, low pH and a big, active yeast population leave little room for anything else. That’s why fruit added after high krausen rarely causes infections, and why fruit in unfermented wort is riskier.

• Aseptic purée is sterile until you open it.
• Frozen fruit isn’t sanitized by freezing, but added to fermenting beer it’s usually fine.
• To pasteurize fresh fruit, heat it to about 160°F (71°C) and hold it for 20 minutes, then cool it; or add it to the whirlpool once the wort drops below about 170°F (77°C) and hold it there for 15–20 minutes. Don’t boil it.

More in our guide to cleaning and sanitizing a fermenter.

Troubleshooting

Problem	Likely cause	Fix
Krausen out of the airlock	Not enough headspace for the refermentation	Fit a blow-off tube; leave more room next time
Blocked valve or dip tube	Pulp and seeds	Bag the fruit; cold crash so solids settle before you transfer
Haze that won’t clear	Pectin	Pectic enzyme; don’t boil fruit
Gushing bottles	Packaged before the fruit sugar finished fermenting	Chill every bottle right away and open over a sink; wait for stable gravity next time
Weak fruit flavour	Too little fruit, added too early, or a mild fruit	More fruit, added later; drink fruit beers young

Frequently asked questions

Do I need a secondary fermenter for fruit?

No. Add the fruit to the primary once fermentation slows. It saves a transfer and the oxygen that comes with it.

How long should fruit stay in the beer?

Until the refermentation is finished and the gravity is stable, usually one to two weeks. Longer doesn’t add much, and fruit aroma fades with time.

Will fruit make my beer stronger?

A little. The fruit’s sugar ferments to alcohol while its water thins the beer slightly. An ABV worked out from your original gravity will read a bit low, because it doesn’t count the fruit sugar.

Which beers work best with fruit?

Light, low-bitterness beers such as wheat beers, blondes and sours, because hop bitterness clashes with fruit acidity. Cherries and raspberries also work well in stouts and porters. Our strawberry blonde ale uses 1 lb of strawberries per gallon.

Does fruit make beer sour?

Tart fruit adds some acidity, but a true sour beer gets its sourness from lactic acid bacteria. See brewing sour beers.

Related guides

Cleaning and sanitizing a fermenter, bottling homebrew, sour beers, wild fermentation, witbier recipe (orange peel and coriander).