Ground Cherry Pale Sour Recipe

Here's a sour beer I've wanted to brew for the past three or so years. It harkens back to a time where I was more enamored with the idea of brewing sour beer with fruit and especially fruit that didn't come from generic supermarket varieties. That's a problem because I'm a terrible gardener and to procure enough fruit for beer requires a bush or tree that would require years of development. I went on the hunt for fruit that would survive Texas summers without too much coddling and wouldn't require years of development before I could even get close to fruit.

What I found was something called a ground cherry.

WTF is a ground cherry?

Ground cherry is a small fruiting plant similar to a tomatillo. It grows like a tomatillo plant and develops small fruit that grow in husks, like a tomatillo. There are a few varieties around the world but the two most common are Aunt Molly (which have a citrus-y flavor) and Cossack Pineapple (you can figure that out). It's most similar to a gooseberry in both appearance and flavor, although it is less acidic (and not actually a gooseberry).

Picture of the plants--not mine

It grows across a wide range of environments. With some watering it survives into the triple digits during summer and hangs on until temperatures drop to 40F like tomatillos and tomatoes. The plant gains its name from the way the fruit grows and drops. Midway through maturity the stem supporting the husked fruit gives and the fruit drops to the ground. It takes an additional few weeks for the fruit inside to reach maturity. The green half-mature fruit is full of solanine, which is the poisonous compound in tomato plants and other related plants. This goes away as the fruit matures into a brighter color, orange for Aunt Molly and goldenrod yellow for Cossack Pineapple.

The fruit is interesting for sure. I opted for the Cossack Pineapple, which at full ripeness has a pineapple and vanilla flavor with a hint of tomatillo. When it's still a little green the vanilla is less present with more of a pineapple-tomatillo-green tomato flavor. Culinary applications range from use like tomatoes or tomatillos in salsas or salads to berry-like applications like pies and tarts.

The fruit grow to between green pea and marble size; that means to procure a decent volume of fruit you need a lot. The good news is that this plant has a high yield of fruit, even with moderate growth. The challenge is that it grows and drops fruit the entire growing season which means collecting fruit and probably freezing to get a decent yield. It's taken two years to collect one pound but that is one plant the first year and two plants the second year, minus the volume I ate instead of setting aside for beer. To obtain enough in a single year for a five gallon batch I would need several healthy plants and keep from eating too many. 

The inside of the fruit contains a lot of seeds which may be an issue for beer. I'm slightly concerned that the seeds risk bleeding excessive tannins into the beer. I could try pureeing the fruit but I'm concerned that will tear up the seeds and straining them out would be an absolute PITA. Instead I plan on giving the fruit some pulsed chops in the food processor to break them apart and then plan to avoid long contact time with the sour beer.

Ground Cherry Sour Beer Recipe Design

Nothing to exciting about the recipe design. I wanted to keep the beer pale and fairly neutral to let the fruit flavors shine. While some fruit play nicely with darker sour beers, the flavors of these ground cherries are more compatible with the flavor profile of a pale sour beer with little to no specialty malt. 

I am also still trying to use ingredients on hand so the grain bill was mostly built out of a "what can I sling together to get in the vicinity of what I need to brew" than trying to craft the perfect recipe. I have a clump of white wheat malt which will make up the bulk of the grain bill. Of all the beers I've had with a strong pineapple flavor, they all seem to have a large portion of wheat so I felt this was a good fit. The rest of the recipe is designed to keep on the path of a lighter beer with low IBUs and only a little munich malt to add a little maltiness around the pineapple and vanilla flavors.

Ground Cherry Pale Sour Beer Recipe

Details
Batch Size: 1 gallon
Est. ABV: 5.3%
Est. IBU: 15
Est. OG: 1.052
Est. FG: 1.011
Est. SRM: 4.7
Expected Efficiency: 72%
Grain Bill	Pounds		Ounces		SRM		Pct. Grist
Pilsner malt			14		2		46.80%
White wheat malt			12		2		39.90%
Munich malt			4		9		13.30%
Water Profile	ppm
Bru'n Water Yellow balanced Profile
PH: 5.5
Calcium	50
Magnesium	7
Sodium	5
Sulfate	75
Chloride	62
Bicarbonate	1
Water Additions					Mash		Sparge
Gypsum					0.2g		0.3g
Epsom Salt					0.2g	0	0.2g
Canning Salt
Baking Soda
Calcium Chloride					0.2g		0.4g
Chalk
Pickling Lime
Lactic Acid
Mash Schedule	Step Temp.				Step Time
Single infusion mash
Mash volume: 0.58 gal
Sparge volume: 0.9 gal
Infuse 0.58 gallons at 167F	150F				75
Sparge 0.9 gal at 190F
Boil Schedule	Volume		Unit		Time		IBU
60 minute boil
Belma [12%]	0.06		oz		60		14.9
Fermentation Schedule	# Days		Temp.
Yeast: Oregon Special
Pitch 100ml slurry
Pitch at 70F	?		Ambient
Add 1lb ground cherries
Bottle to 4 vol CO2 with 1 oz table sugar

Brewday and Fermentation Notes

Brewed on 3.26.17.

All that wheat turned into a stuck mash. Not fun.

Preboil volume: 1.4g
Preboil gravity: 1.035
Mash efficiency: 79%

Postboil volume: 1.00 gal
Postboil gravity: 1.043
Brewhouse efficiency: 60%

Yikes to that efficiency. I'm not terribly worried about this batch having too low of gravity because it's mostly a vessel to test out the ground cherries, otherwise I would have hit it with some DME at the end of the boil.

6.13.17: Tasted beer, already pretty sour and flavorful so time for some fruit. I had the fruit frozen so I gently warmed in a pan before transferring to the food processor to puree. That turned one pound of tasty whole ground cherries into this puree.

Not the best looking puree but it tastes pretty good. They held up well to freezing. I could only fit about 12 oz. of the puree into the fermentation vessel. I'll let it ride for a few weeks and then taste. If it needs more fruit I'll have to rack over to another gallon jug with the remainder. Not my preferred course of action though.