13,591
edits
Changes
m
no edit summary
An in-house experiment at Bell's Brewery by Timothy Lozen demonstrated similar flavor differences in wort soured with a selection of different strains: ''L. brevis'' from Bell's Brewery, ''L. casei'' (White Labs), ''L. buchneri'' (White Labs), ''L. delbruekii'' subsp. ''bulgarius'' (ATCC #11842), ''L. plantarum'' (Goodbelly), and ''L. rossiae'' (White Labs). The wort soured with ''L. bucherni'' was the most preferred with a score of 5.9, followed closely by ''L. casei'' which scored 5.3, ''L. brevis'' wich scored 4.9, ''L. plantarum'' which scored 4.6, and ''L. rossiae'' which scored 4.3. The ''L. delbruekii'' subsp. ''bulgarius'' scored lowest on preference with a score of 1.6, and was characterized as "cheesy/pukey and funky". ''L. casei'' was characterized as the most sour, while ''L. buchneri'' was characterized as the most citrusy and ''L. plantarum'' was characterized as the most fruity. The different strains also produced a range of titratable acidity and diacetyl with ''L. casei'' producing the most and ''L. delbruekii'' subsp. ''bulgarius'' the lowest titratable acidity and the most diacetyl. ''L buchneri'' produced the most alcohol at 0.64% ABV <ref name="lozen_2017">[https://www.mbaa.com/meetings/archive/2017/proceedings/Pages/92.aspx Timothy Lozen. "A comparison of selected lactic acid bacteria for use in the production of sour wort and beer." Presentation by Bell's Brewery for the 2017 Master Brewers Conference. 2017.]</ref>. See also [https://www.masterbrewerspodcast.com/085 MBAA podcast #85 with Tim Lozen].
Another study showed that ''L. plantarum'' produced significantly more diacetyl, acetoin (yogurt-like flavor), and acetaldehyde than ''L. reuteri'' and ''L. brevis''. These three compounds were associated with dairy-related notes of "buttery", "lactic", and "yogurt" flavors identified during sensory testing <ref name="Peyer"></ref>. Some LAB can release these compounds through the catabolism of citric acid, which is found in wort. Ester production is generally insignificant, although significant ester formation has been found during malolactic fermentation in red wines, and ethyl acetate has been found to be produced in malt based beverages <ref name="peyer_review">[http://www.sciencedirect.com/science/article/pii/S0924224415300625 Lactic Acid Bacteria as Sensory Biomodulators for Fermented Cereal-Based Beverages. Lorenzo C. Peyer , Emanuele Zannini , Elke K. Arendt. 2016.]</ref><ref name="Tenhovirta_masters" />. Acetaldehyde produced from ''L. plantarum'' helps to produce pyranoanthocyanins that stabilize wine's red color <ref>[https://www.sciencedirect.com/science/article/pii/S0963996918302084 Acetaldehyde released by Lactobacillus plantarum enhances accumulation of pyranoanthocyanins in wine during malolactic fermentation. Shaoyang Wanga, Siyu Lic, Hongfei Zhaoa, Pan Gua, Yuqi Chena, Bolin Zhanga, Baoqing Zhu. 2018. https://doi.org/10.1016/j.foodres.2018.03.032]</ref>. Some strains may also produce fusel alcohols and other off-flavors. For example the referenced study found an accumulation of the fusel alcohol n-Porponal in the sample of ''L. reuteri'', and a small decrease of isovaleric acid coupled with a small increase of [https://en.wikipedia.org/wiki/Hexanoic_acid hexanoic acid] by ''L. brevis'', ''L. plantarum'', and ''L. reuteri'' (only 0.25-0.32 mg/L was found, and the flavor threshold of hexanoic acid is 5.4 mg/L <ref>[http://www.leffingwell.com/odorthre.htm Leffingwell & Associates website. Odor Thresholds. Retrieved 12/30/2015.]</ref>) <ref name="Peyer"></ref>. Heterofermentative species can also produce [[Tetrahydropyridine|tetrahydropyridines (THP)]], which is the cause of "mousy" off-flavors <ref name="Costello">[http://pubs.acs.org/doi/abs/10.1021/jf020341r Mousy Off-Flavor of Wine: Precursors and Biosynthesis of the Causative N-Heterocycles 2-Ethyltetrahydropyridine, 2-Acetyltetrahydropyridine, and 2-Acetyl-1-pyrroline by Lactobacillus hilgardii DSM 20176. Peter J. Costello and Paul A. Henschke. 2002.]</ref>. Aldehydes (2-methyl-1-propanal, 2-methyl-1-butanal, 3-methyl-1-butanal) and their associated non-fusel alcohols (2-methyl-1-propanol, 2-methyl-1-butanol, and 3-methyl-1-butanol) can be produced from amino acids such as leucine, isoleucine, and valine to form fruity flavors <ref name="peyer_review"></ref>. A few species, especially most strains of ''L. fermentum'', and some strains of ''L. delbrueckii '' subsp. ''bulgaricus'', can produce ropiness in the form of exopolysaccharides, similar to [[Pediococcus]] <ref name="peyer_review"></ref>.
[http://www.sciencedirect.com/science/article/pii/S0308814617302911#t0005 Dongmo et al. (2017)] found 56 volatile flavor compounds, including various esters, alcohols, ketones, aldehydes, acids, ethers compounds, sulfur compounds, heterocyclic compounds, phenols (including guaiacol and 4-vinylguaiacol), terpenes, lactones, and several unidentified compounds. Key compounds produced by ''Lactobacillus'' include acetaldehyde (thought to be a major flavor contributor to kettle soured beers <ref name="Peyer_2017" />), β-Damascenone, furaneol, phenylacetic acid, 2-phenylethanol, 4-vinylguaiacol, sotolon, methional, vanillin, acetic acid, nor-furaneol, guaiacol and ethyl 2-methylbutanoate. Acetaldehyde was the most impactful aroma compound found followed by propan-1-ol and γ-dodecalactone. Acetaldehyde was generally produced in much higher amounts (~23-64 µg/L) by the select strains of ''L. plantarum'', while ''L. amylolyticus'' and ''L. brevis'' produced only 1.5-3 µg/L. In fact, the levels of all of these compounds differed significantly based on the species and strain. The selected strains of ''L. brevis'' were associated as having worse aromas that were dominated by methional (cooked potatoes), acetic acid (vinegar), and nor-furaneol (caramel-like). The ''L. plantarum'' strains selected were identified as producing more positive aromas from compounds such as β-damascenone (apple/fruit juice), furaneol (strawberry), 2-phenylethanol (rose/caramel) and ethyl 2-methylbutanoate (citrus). Small but significant amounts of linalool and geraniol were also found, which are normally terpenes found in [[Hops|hops]]. Vanillan is formed from ferulic acid by some ''Lactobacillus'' species as well as ''Oenococcus oeni'' <ref name="Dongmo">[http://www.sciencedirect.com/science/article/pii/S0308814617302911 Key volatile aroma compounds of lactic acid fermented malt-based beverages – impact of lactic acid bacteria strains. Sorelle Nsogning Dongmo, Bertram Sacher, Hubert Kollmannsberger, Thomas Becker. 2017. doi:http://dx.doi.org/10.1016/j.foodchem.2017.02.091.]</ref>. Some strains of ''Lactobacillus'' can break down chlorogenic acids, which are esters found in plants, into their phenolic derivatives. For example, some strains of ''L. fermentum'', ''L. helveticus'', and ''L. reuteri'' were found to hydrolize chlorogenic acids into caffeic acid, which can then be converted into other phenols such as 4-vinylcatechol and 4-ethylcatechol by ''[[Brettanomyces#Phenol_Production|Brettanomyces]]'' <ref>[https://www.sciencedirect.com/science/article/pii/S0963996918303363 Site-specific hydrolysis of chlorogenic acids by selected Lactobacillus species. Elsa Anaheim Aguirre Santos, Andreas Schieber, Fabian Weber. 2018. DOI: https://doi.org/10.1016/j.foodres.2018.04.052.]</ref>.