Lambic by Jean-Xavier Guinard

Author:Jean-Xavier Guinard [Guinard, Jean-Xavier]
Language: eng
Format: epub
Tags: CKB007000 Cooking / Beverages / Beer
ISBN: 978-1-938469-34-3
Publisher: Brewers Publications
Published: 2016-04-04T16:00:00+00:00

- Lactic acid bacteria -

(3 to 4 months)

After three to four months, the main fermentation is complete. The yeast population decreases, while the bacterial population increases. Most bacterial isolates found during that period are lactic acid bacteria of the genera Pediococcus, of which the predominant species usually is P. damnosus. Some Lactobacillus isolates may also be found. The population of lactic acid bacteria reaches a maximum after seven months, which coincides with the beginning of summer. The warmer temperature in the cellar around that time of the year seems to be required for lactic acid bacteria to grow. Indeed, the same phenomenon is observed during the second year of the lambic fermentation; that is, the population of lactic acid bacteria peaks again at the onset of the second summer. We suspect that one way to speed up the lambic fermentation would be to set the casks at a warmer temperature as soon as the main, alcoholic fermentation is complete. This could simply be achieved by having temperature-controlled cellars, a luxury that few lambic breweries can afford because of their old age (the buildings usually are not very well insulated).

Tolerance to hop antiseptic is important in P. damnosus, which grows in hopped wort while other species of lactic acid bacteria are inhibited. As lactic acid bacteria, P. damnosus ferment glucose into lactic acid without emitting carbon dioxide. Their presence in the lambic fermentation coincides with the large increase in lactic acid concentration observed after a few months. Lactic acid is responsible for the sour taste of lambic beers. It is definitely one of the key components of lambic flavor. The increase in lactic acid concentration during bacterial proliferation is rather slow, however, because these bacteria are very fastidious (slow-growing, with complex nutritional requirements) and never reach a very high cell density in the lambic wort. P. damnosus strains readily produce acetoin and diacetyl which may contribute a buttery aroma to the beer. Diacetyl concentrations of greater than 200 ppb are produced by Pediococcus. However, these levels later drop to about 45 ppb (Van Oevelen et al.; 1978).

Frequently, a disorder develops at this stage of the lambic fermentation that makes the beer oily or even ropy. The ropiness may be accompanied or followed by a haze that cannot be eliminated by filtration. In 1900, Van Laer published the first account of a rope-forming bacterium in lambic worts. The bacterium, which was called Bacillus viscosus bruxellensis at the time, was thought to be responsible for the appearance of ropiness in some casks. This disorder is caused by some strains of P. damnosus (formerly P. cerevisiae), which may produce slime from glucose or maltose in the wort (Van Oevelen and Verachtert; 1979). The slime is composed of carbohydrates, nucleic acids, and proteins. Its effect is only aesthetic, and it is not harmful to the consumer. Fortunately, if slime is produced, it is usually hydrolyzed later during the lambic fermentation by growing cells of Brettanomyces yeasts.

It is also worth mentioning the occasional presence of some

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