Couple questions about my Lactobacillus plantarum starter

[Juno_Malone]

Quick backstory - I'm planning on brewing my first kettle-soured beer this weekend (a lime Gose). My plan is to mash on Friday afternoon, cool, pitch my L. plantarum starter, let sour for ~48 hours (I don't have a way to measure pH, so I'm just going to go with whatever level of sour I get), and then resume with boiling on Sunday afternoon.

I ordered these L. plantarum caps off Amazon, which it sounds like a lot of folks have had success with. Last night I made a 1L batch of 1.035 starter using golden DME, and emptied 6 of the capsules in to it. Using a heating pad I'm able to keep the starter slightly above 80F. My questions:

1. It's a 1L starter in a 1-gallon glass jug, meaning there's a lot of headspace. I know that oxygen isn't necessarily bad for L. plantarum, but I'm worried that it might result in the production of acetic acid or hydrogen peroxide. Is this something I should be moderately worried about? I don't really have any way to purge the headspace regardless. But I could transfer it to a smaller vessel, perhaps a mason jar or a growler.
2. I'd read mixed opinions on how long to let the starter go before pitching it in to your cooled (unhopped) wort. I decided to err on the longer side, because I wasn't sure how hot I'd be able to keep the starter so I figured the bacteria might be working a little slowly. This means that my starter will be sitting around 80-85F for 4 days prior to pitching - is this too long? Do I need to worry about the bacteria running out of sugar and starting to convert the lactic acid it's produced to acetic acid/hydrogen peroxide?

Thanks for any advice!

 

[stz]

I've done two sours with plantarum from probiotic capsules. I sparged hot (80C) to help sanitise the wort and collected extra when brewing a regular batch for the experiment. First was around 14 billion cells directly into 20L of wort which was kept in a sealed container for 5 days. I waited until the temperature dropped below 40C and kept it in a switched off chest freezer, it stayed above 30C for the first 24 hours. I added some lactic acid first to bring the pH down to a safer level and discourage competing organisms and while I had a reading from the mash, it was very much an estimate (20ml in 20L). This soured, but didn't sour very much and I ended up pitching the contents of some more capsules and waiting until day 7 to boil. The wort looked kind of gooey by day 6, but I had no sign or indication of anything yeasty or untoward going on (clean sour taste, no co2 production, slightly bread like smell).

The second was similar, but I tested pH for my lactic addition and I took better temperature readings. I pitched much more, like 40-50 billion cells. This soured to a level I found appropriate within 4 days and never looked any different by the time I proceeded to boil.

What would I change? I would make a starter like you intend to do. The cell count for plantarum is quite high compared to bruxis, like 150 billion cells for 20-25L of wort. I would try and hold temperature better, because I'm sure that and cell count is the reason why I didn't get there in 48 hours. That or I'd just use bruxis. I would stress less about acetic.

In terms of flavour? My first beer I hopped too heavily. The flavour is very much like shandy (beer and lemonade mix). It tastes too much, but not quite like beer and I think I didn't correctly utilise the sour aspect. My second beer got lemon and lime zest at whirlpool and only a few aroma hops, it tastes a little like sprite or 7up, again it is weird and I think I need to think about what I'm doing a little more.

Of course with these first attempts I'm happy to produce something which can even be consumed.

 

[Juno_Malone]

Thanks for the advice! I think I will try to pick up some pH strips...that way, if it's not low enough after 48 hours, I'll let it ride a few more days and just brew mid-week instead of Sunday.