Lactic acid bacteria inoculation timing

When the diastase of the malt has had time to act the mash is inoculated with a smaller special mash of rye and malt in which a pure culture of lactic acid bacteria (Bacillus delbruckii) is growing. The mash is now incubated for about sixteen hours at the proper temperature (ca. 50° C., 1220 F.). During this time the proteins of the grains are partially hydrolyzed and some lactic acid is formed. The liquor now contains largely sugars, resulting from the action of malt diastase on the starch, lactic acid, amino acids, and other hydrolysis products of the proteins, all in a highly assimilable form for the yeasts, and the cellulose residues from the cereals. 

Next the mash is cooled to about 55° and acidified by inoculation with pure cultures of lactic acid bacteria. The purpose of this acidification is to protect the mash from the action of putrefactive bacteria and at the same time to create a condition in the mash which hastens peptonization of the proteins. When the acidification of the mash has reached about 1.6% acid it is sterilized, filtered, cooled and passed into the yeast fermentation tank. 

Although species diversity in a must can increase shortly after crush, viable cell number normally remains relatively low (<10 to 10 CFU/mL) for some period of time (Lonvaud-Funel et al., 1991). Even if inoculated prior to alcoholic fermentation, most lactic acid bacteria experience a rapid die-off during alcoholic fermentation, commonly to populations below lOOCFU/mL. As an example, Edwards et al. (1990) observed the population of O. oeni decrease from 10 CFU/mL to less than 30CFU/mL, resulting in a delayed malolactic fermentation. Sometime after completion of alcoholic fermentation, the population of Oenococcus oeni may increase... 

Malt wine is made from fermented malt extract (the hot water extract of whole meal malt). Mal-ton wine is made in the same way, except that sucrose is added at 1.8-times the amount of malt in order to increase the sugar and alcohol content of the wine. The wort is then soured by the action of lactic acid bacteria (0.6-0.8% lactic acid, final concentration). The acid fermentation is stopped by heating the wort to 78 °C and, after inoculation with a pure yeast culture, the wort is fermented to an alcohol content of 10-13%. The beverage thus formed has the character of a dessert wine, but is different because of its high content of lactic acid and its malt extract flavor. Mead is an alcoholic liquor made of fermented honey, malt and spices, or just of honey and water (not more than 21 water per kg of honey). Since early times, mead has been widely consumed in Europe and, even today, it is enjoyed the most of all the wine beverages in eastern and northern Europe. 

When yeasts and lactic acid bacteria are inoculated in approximately equal concentrations (7 x 10 UFC/ml), lactobacilli are completely eliminated after 8 days. O. oeni disappears more slowly and subsists at a very low concentration. If the same must is inoculated with 10-100 times more bacteria, they remain viable for a longer period but evenmaUy disappear—with the exception of O. oeni. This species is better adapted than the others to winemaking. 

The growth of malo-lactic bacteria in wines is favored by moderate temperatures, low acidity, very low levels of S02, and the presence of small amounts of sugar undergoing fermentation by yeast. It is frequently possible to inoculate a wine with a pure culture of a desirable strain of bacteria and obtain the malo-lactic fermentation under controlled conditions. The pure-culture multiplication of the selected strain of bacteria is difficult, however. It is also difficult to control the time of the malo-lactic fermentation—sometimes it occurs when not wanted, and at other times will not go when very much desired. For the home winemaker it is probably most satisfactory to accept the malo-lactic fermentation if it occurs immediately following the alcoholic fermentation. The wines should then be siphoned away from deposits, stored in completely filled containers at cool temperatures, and have added to them about 50 ppm S02. If the malo-lactic fermentation does not take place spontaneously and the wine is reasonably tart, the above described regime of preservation will likely prevent its occurrence. When the malo-lactic transformation takes place in wines in bottles, the results are nearly always bad. The wine becomes slightly carbonated, and the spoiled sauerkraut flavors are emphasized. 

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