Asked this on HomeBrew too, but hoping to see all the different takes on this.. Making a Gose with a buddy. Have a 1L starter going with Lacto Delbrueckii. Doing a mash, boiling for 15min to sanitize the wort, then pitching lacto starter. After a week or so when we do the second boil to add hops and kill the lacto, how much DME should we use to replace the sugar that was eaten from the first lacto fermentation? Our starting OG is going to be 1.045 and want to finish at 4.7%. Thanks
Average wort sugar composition: L. delbrueckii subspecies are the number and types of substrates it can metabolize. As noted, such properties are restricted to enzyme expression within its genome. L. delbrueckii subsp. bulgaricus and subsp. indicus can metabolize lactose, glucose, fructose, and mannose. In addition to these, L. delbrueckii subsp. lactis catabolizes galactose, sucrose, maltose, trehalose and other modified carbohydrates. The exact answer depends on which subspecies of lacto D you are using. It also depends on the actual sugar composition of your wort which will be unknown unless you used extract or have the ability to analyse the sugar content of your wort. It also depends on how well the Lacto D performed by the time you are ready to add more DME. There may be several unknowns, but a reasonable estimate can be made.
Just make sure your second brewday OG is 1.045, don't worry about math and such. If you are pitching the Lacto pre-boil and doing a sour wort, when you re-boil the following week you are driving off any alcohol and CO2 produced by the Lacto, leaving behind only the acid and remaining sugars. At this point just adjust the sugars to get your 1.045 after the second boil and your good to go. Once converted by the Sacc strain you will have only ABV increase.
