Unlike British and French breweries that were by the mid 19th century using wort chillers, Belgians were still cooling all their beer in large pans known as "coolships." Lacambre emphasized that a "viscous fermentation" came when the temperatures were too high.
“The cooling of the containers must be prompt, the condition is most essential, especially in summer because that is very likely to alter it in the hot season. The taste and smell, which are spread by contact with the greatest ease...from a profound alteration suffered by some of the wort often on the end of cooling.”He relates an experience he had as a brewer when during a summer storm, a batch of cooling beer "became disturbed"--I think by crashing thunder, but it's not clear--and had become bubbly. He tried to save the beer, but it was putrid. He didn't understand the mechanism, but he knew the result of contamination was highly contagious worth that would spoil other wort it came into contact with. This is what he concluded:
“The result was strongly affected the taste and the more or less nauseating odor which is the true character of this kind of alteration. The smell is so characteristic that an experienced man can easily...recognize this kind of alteration simply smelling beer that has received the slightest breach of versoemer or taste of summer.... This kind of alteration, which always produces the bad alcoholic fermentation which many brewers have given the name of wild fermentation, because it still offers the symptoms unrelated to a good fermentation.”Lacambre was convinced beer, or at least wheat beer, needed to rest in coolships to "release nitrogenous material"--whatever that meant. He classified different types of fermentation based on their qualities: "the alcoholic fermentation of glucose, lactic acid, acetic acid, viscous and putrid." He was so close to having figured it out himself. In just six years, Pasteur identified the mechanism:
"In 1856, a man named Bigo sought Pasteur's help because he was having problems at his distillery, which produced alcohol from sugar beetroot fermentation. The contents of his fermentation containers were embittered, and instead of alcohol he was obtaining a substance similar to sour milk. Pasteur analyzed the chemical contents of the sour substance and found that it contained a substantial amount of lactic acid instead of alcohol. When he compared the sediments from different containers under the microscope, he noticed that large amounts of yeast were visible in samples from the containers in which alcoholic fermentation had occurred. In contrast, in the polluted containers, the ones containing lactic acid, he observed "much smaller cells than the yeast." Pasteur's finding showed that there are two types of fermentation: alcoholic and lactic acid. Alcoholic fermentation occurs by the action of yeast; lactic acid fermentation, by the action of bacteria."The "taste of summer" was buggies, allowed more time to infect a more slowly-cooling wort. Less poetic, but a revolution in understanding how beer ferments.