I might be the only poster on HBUK interested in this but I am writing this up for my own benefit and hopefully anyone else who fancies a go, or stumbles across this via Google. I first came across this method a few days ago on HBT here... (big thanks to RPh_Guy) ....
(And via the link he provided to his wiki page which provides more info... https://modernbrewhouse.com/wiki/Sour_beer )
"Making sour beer doesn't need to be complicated! These techniques are a good alternative to the antiquated kettle souring method.
- Make unhopped wort. Chill as normal.
- Pitch Lactobacillus plantarum and the yeast of your choice.
- Ferment as normal, at 65°F or higher.
- Optional/recommended add hops when it reaches the desired sourness. (Dry hops or hop tea)
- Package as normal.
Same as co-souring, except pitch the Lactobacillus after 1-2 days of fermentation (or 8-12 hours if using kveik and fermenting hot).
Post-souring is designed to maximize yeast flavor. It's great if you want to use an estery yeast like WLP644 (Sacc Trois) for example, which adds a nice tropical pineapple & mango profile." (elsewhere he recommends making a starter for the bacteria if you are delaying pitching it).
I previously believed that kettle souring was the quickest simplest method for making sour beers. But the method described here involves making beer as normal, but pitching Lactobacillus Plantarum in the FV with a regular saccharomyces yeast. Mash, boil, cool, then pitch yeast and lacto. The only other difference really is that you don't hop the beer at all until the wort is soured to the level you want (either test the pH or taste test). You add dry hops or a hop tea at that point, but you don't generally use much hops in a sour - they are really there just to stop the souring and protect the beer against infection thereafter. Sourness replaces bitterness.
Most brewers using Plantarum seem to buy probiotic capsules or drinks made solely with Plantarum, like Swanson's capsules and Goodbelly drinks. It turns out that Lallemand Wildbrew Sourpitch is pure Plantarum. There are probably cheaper ways to buy Plantarum, but the info is useful at least.
WildBrew™ Sour Pitch is a ready-to-use, high-performance, and high-purity lactic acid bacteria specifically selected for its ability to produce a wide range of sour beer styles. WildBrew™ Sour Pitch produces a clean and balanced citrus flavor profile typical of both traditional and modern sour beer styles. When inoculated at optimal temperature and the right conditions, it is a powerful, safe and easy way to handle bacteria for various beer souring techniques, such as a typical kettle souring process. Styles which can be brewed with WildBrew™ Sour Pitch include, but are not limited to, Berliner Weisse, Gose, lambic-style, American Wild, and Sour IPA. WildBrew™ Sour Pitch will deliver unmatched consistency, effortless application, fully assured performance and unparalleled purity for brewing the sour beer style of your choice.
- Fast pH drop that can be completed within 2 days (typically within 24 to 36 hours).
- High lactic acid versus lower acetic production.
- Aroma and flavor is citrus and tangy with a hint of fruit.
The optimal temperature range for WildBrew™ Sour Pitch when producing sour beer styles is between 30°C to 40°C (86°F to 104°F). Fermentation rate, fermentation time and pH drop are dependent on inoculation density, bacteria handling, fermentation temperature and nutritional quality of the wort.
Using a rate of 10g/hL inoculate wort with Wildbrew™ Sour Pitch. (so only 2g in 20 litres, which means a pack in theory could make 5 batches, so 7 quid or so doesn't seem bad). Lallemand says store it in the freezer..
"Please store WildBrew® Sour Pitch in the freezer until you need it next. You can easily freeze/defrost when needed. It is very different than dry yeasts."
Wikipedia says: Lactobacillus plantarum can grow in the temperature range 12 °C to 40 °C.
And: It is also present in saliva (from which it was first isolated).
And: L. plantarum are aerotolerantGram-positive bacteria that grow at 15 °C (59 °F), but not at 45 °C (113 °F)
Lallemand Flavour/Aroma wheel:
This is the Lallemand suggested method (pdf download): https://www.lallemandbrewing.com/docs/products/bp/BEST-PRACTICES_KETTLESOUR_DIGITAL.pdf