Changes

Different strains of ''Lactobacillus'' are known to have different nutrient requirements, including some metal ions. ''Lactobacillus'' requires manganese, magnesium, potassium, and sodium, with manganese and magnesium being crucial for their growth. Brewer's wort has many of these nutrients naturally, although zinc is generally deficient. One study looked at WLP672 (''L. brevis'') and found that an increase of magnesium resulted in a faster souring phase, while zinc additions slightly slowed the souring phase. This suggests that in at least the case for this strain of ''L. brevis'', zinc additions should be added after the souring phase for yeast health. Excess magnesium could lead to negative flavor contributions to beer, so magnesium additions should be limited to not exceed 30 mg/l <ref>[https://www.brunwater.com/water-knowledge "Water Knowledge." Martin Brungard. Bru'n Water website. Retrieved 12/02/2020.]</ref>. The addition of zinc also had several effects on the flavor and aroma compounds produced. Therefore, experimenting with different nutrient additions for the souring phase may result in widely different tasting beer <ref>[https://www.mdpi.com/2218-273X/10/12/1599 Chemical Composition of Sour Beer Resulting from Supplementation the Fermentation Medium with Magnesium and Zinc Ions. Aneta Ciosek, Katarzyna Fulara, Olga Hrabia, Paweł Satora, and Aleksander Poreda. 2020. DOI: https://doi.org/10.3390/biom10121599.]</ref>. See [https://www.facebook.com/groups/MilkTheFunk/permalink/4107425732618943 this MTF thread] for more commentary on this study.