Do you mind explaining a little more why you believe kettle souring is antiquated, harder, and has more risk of contamination? Still learning here, and your point of view would be very helpful.
Sure, happy to help.
Your kettle souring process is fine, although most brewers also pre-acidify to pH 4.0-4.5 to improve head retention and prevent or reduce impact from potential contaminants.
Advantages of co-souring or post-souring (which I will refer to as "modern methods")
versus kettle souring :
Simplicity.
The modern method brew day fits into one day and is basically the same as any other brew day.
Modern methods are good with only one boil, or no boil. Kettle souring involves two separate boils ideally, and two chilling steps.
Modern methods do not require maintaining a controlled high temperature in the brew kettle. A kettle sour doesn't require heat either, but it does take longer to sour at lower temperature which increases contamination risk.
Modern methods do not require CO2 purging or pre-acidification. Arguably these aren't needed for kettle sours either but there are potential downsides to not using these additional steps when kettle souring.
Modern methods do not require an increased yeast pitching rate. It's often recommended to increase pitch rate for kettle sours under pH 3.5 to reduce yeast stress and guarantee a good attenuation.
Modern methods better tolerate low Lacto pitch rates and therefore never require a Lacto starter.
Faster.
Modern methods shave off however many days that it takes for the separate souring step.
Modern method sours ferment faster because the yeast goes through it's normal lag and growth phase without being inhibited by acidity. The acidity is slowly increased throughout fermentation so the yeast is never acid shocked.
Safer.
Wort is a microbe growth medium, especially unhopped wort without healthy yeast activity. A huge spectrum of microbes would love the opportunity to feast on the malt sugars at 95°F. Higher temps are needed for inhibition. MTF recommends 113-120°F for sour mashing. Sauergut is generally held at 118°F. However,
L. plantarum itself cannot tolerate these temperatures.
Kettle soured batches experience contamination at seemingly a much higher rate (during the souring phase) than non-sour batches. The risk is obviously high. The kettle isn't designed to be air-tight or fitted with an airlock, and it pulls in ambient air full of microbes any time it starts to cool.
Modern methods provide far less opportunity for wild microbes to gain a foothold in the wort because the wort isn't sitting unprotected. A normal yeast fermentation provides a great deal of natural protection against wild microbe activity by removing oxygen, lowering pH, producing alcohol, and removing nutrients. And CO2 production maintains positive pressure, keeping out microbes during fermentation.
L. plantarum itself will not cause contamination.
Better tasting.
Acidity greatly suppresses yeast expression. Therefore yeast add little or nothing to the flavor profile in kettle soured beer.
Bacteria add desirable flavor. Boiling removes a lot of it.
These factors tend to produce kettle sours that are rather bland and one-note. This is probably the main reason adjuncts are so frequently used.
By comparison modern methods can produce nice complex beers that are quite fruity using the variety of fruity yeast strains available. No adjuncts needed.
Modern methods boil at an "optimal" pH for the chemistry that happens during the boil, potentially reducing off-flavors and staling compounds. YMMV.
With both Co-Souring and Post-Souring, if the lacto addition is somehow tainted, I have no control over it. I also have no control over how sour it will go, and typically can't add a hop addition.
The plantarum cultures we have available aren't "tainted". Your worries are unfounded; it's been widely demonstrated that we use clean cultures.
I'm not sure how kettle souring would be any better even if they were -- the high temp and lack of yeast fermentation would encourage off-flavors.
Sourness is just as easy to control if not moreso with modern methods. Simply add hops when it reaches the desired sourness. Easy Peasy!
The souring process occurs more slowly, so it's easier to catch it near a particular pH if you want to stop it from souring further.
Also, since the beer is fermented to some degree, it's easier to taste the sourness since there's less sweetness in the beer, making it easier to judge the sourness by taste.
Advantages to kettle souring:
It might be better to kettle sour if you're making a "sour IPA" and want to use a lot of hops and add a substantial amount of bitterness? A kettle sour may or may not be easier than making a large hop tea with a complex hop schedule or making a separate batch for blending. However hop tea has been super awesome at adding hop flavor in my experience.
If you like an exceptionally clean (lager-like) and one-note sour, then kettle souring is definitely the way to go.
Hope this all makes sense. Happy souring!
