Butyric Acid Off-Flavors in Beer: Origins and Control

The Microbiology of Malting and Brewing

“…can cause excessive acidification and nitrosamine formation by reduction of nitrate to nitrite (197,198). Growth of Clostridium in the mash or in wort can produce high levels of butyric acid, giving the beer a cheese-like aroma (199). Excessive bacterial growth on malt can also retard mash filtration, probably due to production of dextrans (200), and suppression of bacterial growth has been shown to improve the filterability, extraction efficiency, and nitrogen yield during mashing (192).…”

The microbiology of alcoholic beverages

“…B. coagulans, B. stearothermophilus) and Clostridium present as contaminants of the malt and adjuncts and are capable of growth at the temperatures of mashing, leading to acidification and off-flavours in the wort through the production of lactic and butyric acids. Also, they could contribute to nitrosamine formation in beer through reduction of nitrate to nitrite (Hawthorne et al, 1991;Smith et al, 1992). Boiled wort, although containing anti-microbial factors extracted from the hops, is a nutritious medium and will support the growth of a wide range of bacterial species.…”

Brewing microbiology - bacteria of the genus Clostridium

“…Do pivovarských provozů vstupují tyto bakterie většinou se surovinami a jejich výskyt byl také potvrzen ve vegetativní formě v pivovarských meziproduktech (sladina, mladina). V těchto substrátech či meziproduktech dochází díky metabolické aktivitě bakterií Clostridium k tvorbě celé řady nežádoucích látek, které mohou být odpovědné za změnu senzorického profilu hotového piva (Hawthorne et al, 1991;Storgårds, 2000). Díky značné odolnosti endospor jsou klostridie velmi těžko odstranitelné z pivovarských provozů (Suzuki, 2015).…”

“…It has been shown that the representatives of genus Clostridium may enter the brewery with hops, malt (milled moist malt stored for a longer period of time), or malt substitutes (unmalted barley, starch extracts, syrups and concentrates; malt extracts; glucose syrups; etc.) (Back, 2005;Bokulich and Bamforth, 2013;Hawthorne et al, 1991;Storgårds, 2000). In connection with the contamination of feedstocks, the publications mention species C. acetobutylicum, C. cellulovorans and C. thermocellum, which were detected in malt (Leschine, 2005); C. tertium, which was detected in a glucose syrup storage tank (Hawthorne et al, 1991).…”

“…Bacteria of the genus Clostridium usually enter the brewing operations with raw materials and their occurrence was also confirmed in the vegetative form in intermediate brewing products (wort, boiled wort). In these substrates or intermediates, a number of undesirable substances can be produced due to the metabolic activity of Clostridium bacteria, which may be responsible for changing the sensory profile of the finished beer (Hawthorne et al, 1991;Storgårds, 2000). Thanks to the strong resistance of their endospores Clostridium bacteria are very difficult to remove from the brewing operations (Suzuki, 2015).…”