Naturally occurring yeast on dates?

[DerCribben]

So I found an article about the oldest beer recipe and it calls for dates, for the wild yeast that grows on it. I'll post the recipe as it appeared on byo.com after but first my question is, what strain of yeast would likely naturally occur on dates? What's the likelihood that the yeast on the dates I get would be the same as the ones from Mesopotamia all those years ago? Anyway, here's the recipe:

Ninkasi Hymn Beer Recipe

(5 gallons/19 L)
OG = 1.062 FG = 1.009 ABV = 6.9%

Ingredients

4.5 lbs. (2.0 kg) Weyermann rauchmalz (smoked malt)
3.5 lbs. (1.6 kg) bappir (“beer bread&rdquo
1.5 lbs. (0.68 kg) rice hulls
1.5 lbs. (0.68 kg) honey
1 gallon (3.8 L) date wine
Step by Step

Make the date wine (see below), then bake the bappir (see below) one or two days later. Let bappir cool overnight. The next day, add crushed malt and crumbled bread to your kettle. Mash in to 131 °F (55 °C) with 3.0 gallons (11 L) of water. Immediately begin slowly heating the mash to 156 °F (69 °C), stirring constantly, then rest at 156 °F (69 °C) for 45 minutes. Heat mash to 170 °F (77 °C) and transfer it to your lauter tun. Stir in rice hulls. Let sit for 5 minutes, then recirculate briefly and run off wort to kettle. Collect 4.0 gallons (15 L) total. Boil for 15 minutes, then cool to 70 °F
(21 °C). Remove bag of date skins from fermenter. (If you can get a friend to hold the bag, you can use two cookie sheets to gently press the pulp and yield a bit more juice.) Combine fermenting date wine with your fresh wort, then stir in honey. Add water to make
5 gallons (19 L), aerate and let ferment at 70–80 °F (21–27 °C) until fermentation subsides. Keg or bottle.

Date Wine

(1.0 gallon/3.8 L, fruit wine)
OG = 1.092

Ingredients

3.5 lbs. (1.6 kg) dates
Step by Step

Pit dates and place them in a large nylon grain bag. Put fruit bag in the bottom of a sanitized bucket fermenter and crush the fruit with a potato masher (or your feet). Add water to make 1 gallon (3.8 L). Let the wild yeast on the fruit begin to ferment the juice.

Bappir (Beer Bread)

Ingredients

3.0 lbs. (1.4 kg) Weyermann rauchmalz (smoked malt)
1.0 lb. (0.45 kg) unbleached (wheat) flour
1.25 lbs. (0.57 kg) honey
Step by Step

Grind barley malt into flour. Combine dry ingredients in a large mixing bowl. Fold in honey. Slowly add water and knead dough until it is roughly the consistency of cookie dough. Form dough into large, flat loaves about one inch (2.5 cm) thick. Bake at 350 °F (176 °C) on a pizza stone until outside browns. Remove from oven and let cool. Cut cooled bread into "logs" about 1.5 inches (3.8 cm) thick (think biscotti). Rebake at 350 °F (176 °C) until bread just hardens. Let cool overnight.

 

[david_42]

Not likely to be the "old time" yeast, but 99% chance it will be a bread/ale yeast; unless you live near a Trappist Monastery.

 

[DerCribben]

So wild fruit yeasts tend to be ale or bread yeasts?

 

[gibby15]

I made this at the beginning of summer and it was a total fail. It fermented well for about a week then it slowed down to practically nothing. I assumed it was done, however when I took a reading it still had a ton of sugar in it and was not even close to being done. I left it alone for two months hoping it would slowly ferment. Two months later there was still the same amount of sugar in there and it tasted extremely sour, a very vinegar like smell and taste. It made me want to barf. I assume it was the wild yeast on the dates that were weak and contributed to this problem. I wish it would of worked cause I bet it would have been quite different than any beer today. Using wild yeast can work, there is just more risked involved.

 

[DerCribben]

I was just reading on the wyeast site that naturally occurring yeast can take 2 years to ferment a batch of beer/lambic! The article is here: http://www.wyeastlab.com/com-lambic-brewing.cfm

 

[Tenspeed]

So wild fruit yeasts tend to be ale or bread yeasts?

Yes, it seems to me they are. I've used the exact same method to get wild yeast for bread.

The problem may be just not enough yeast in the initial culture. I know they should propagate fairly rapidly, but if there aren't enough early on they may let something else take over first, which would give you off flavors. In any event, yes, letting it sit for a year after it develops those terrible flavors would probably be the thing to do if you're the adventurous type.

Back to the recipe. I'd probably make the fruit water, set it on the counter so that I could stir it whenever I walked by, feed it fresh sugar water every 6-8 hours or so over a couple days, then pitch it when it starts foaming within a couple hours of feeding.

 

[theredben]

DerCribben - What you have experienced is exactly the reason why beer used to be consumed within a week of being made. It just did not last very long before going sour.

 

[kellzey]

I wouldn't be surprised if some of the currently produced dates have been treated somehow with something that would prohibit yeast growth.

 

[NicholasAdam]

I personally would also shoot for a beer with a lower OG. Odds are if you get any wild yeast to inoculate the beer, they won't be super strong.

 

[day_trippr]

"Naturally occurring yeast on dates?"

Not in the last ~40 years, thanks...

Cheers!