GB1101560A - Improvements in or relating to processes and apparatus for the production of vinegar by a submerged fermentation of alcohol-containing mashes - Google Patents

Abstract

<PICT:1101560/C6-C7/1> In a process for the production of vinegar by the submerged fermentation of alcohol-containing mashes in successive fermentation cycles, in each of which cycles part of the finished vinegar is removed from the fermentation vat and replaced by fresh mash; a starting mash containing 6-9 grams acetic acid per 100 millilitres and 4-7% by volume alcohol is prepared by either (a) mixing an alcohol-containing mash containing 0-2 grams acetic acid per 100 millilitres and 10-14% by volume alcohol to untreated vinegar which has been produced by submerged fermentation and has been stored with access of air to the still liquid level, the vinegar containing 10-13 grams acetic acid per 100 millilitres and 0.5-1.5% by volume alcohol and consequently containing viable vinegar bacteria, the amount of mash being controlled to provide the above-mentioned concentrations of acetic acid and alcohol, or (b) mixing an alcohol-containing mash containing 0-2 grams acetic acid per 100 millilitres and 10-14% by volume alcohol to vinegar which is virtually free of bacteria and contains 10-12 grams acetic acid per 100 millilitres and 0-0.5% by volume alcohol, the amount of mash being controlled to provide the above-mentioned concentrations of acetic acid and alcohol, and inoculating this mixture with an aerated substrate which has been taken directly from a submerged culture and contains propagating vinegar bacteria; the starting mash is uniformly and finely aerated, the aeration beginning before the addition of the alcohol-containing mash in case (a) and before the inoculation in case (b) and is continued without interruption in both cases (a) and (b); and when an alcohol concentration close to zero is reached, part of the finished vinegar is rapidly removed from the fermenting vat and fresh mash containing 0-2 grams acetic acid per 100 millilitres and 10-14% by volume alcohol is slowly added so as to maintain the temperature constant and effect an immediate, intimate mixing and in such an amount that the concentrations of acetic acid and alcohol correspond to those of the starting mash when the supply has been terminated and the full fermenting volume has been restored. The aeration is effected at a rate of 2.5-6 cubic metres per hour per cubic metre of the entire fermenting volume, regardless of the temporary change of the fermenting volume during the transition between cycles, and a large part of the air, about 80-95%, is recycled during the aeration of the starting mash, until the increase in acidity begins, in order to avoid losses of alcohol and acetic acid. The total concentration of the alcohol - containing mash, which equals the acetic acid concentration in grams per 100 millilitres plus the alcohol concentration in per cent by volume, should not be changed by more than \sB 0.3% in successive fermentation cycles. Nutrient media for the fermentation of Acetobacter are disclosed. The fermenting vat 1, Fig.1, has a charging conduit 3 and pump 2,a discharging conduit 5 which extends from the fermenting vat through a pump 7 and from the top into a vinegar tank (not shown), an air duct 11 incorporating a device 12 for maintaining constant air rate, a regulating valve 13 to a gyroscopic flowmeter 14, a rotor 4, a mechanical scum destroyer 19 connected to an exhaust gas conduit 17 and provided with a conduit 20 for recycling and discharging liquid and scum, a line for recycling air from the conduit 17, a cooling coil 22, which is controlled by a switching thermometer 24 and a controller for controlling the discharge of vinegar and the charging of mash. The motor 18 of the scum destroyer is energized in response to a signal given by two vertically adjustable electrodes 34. The controller comprises a step-by-step switch which has three control positions corresponding to the fermentation stages "current cycle", "discharge" and "charge". The step-by-step switch is stepped to the "discharge" position (pump 7 in operation) by an adjustable time-limit relay, into the "charge" position (pump 2 in operation) by a switch 29 at the low level of the fermenting mash actuated by a magnetic float 27, and into the "current cycle" position (cooling coil 22 in operation) by a switch 28 at the upper level also actuated by the magnetic float 27. During the charging magnetic float 27 actuates a switch 30 whereby the continuing operation of the charging pump 2 is reponsive to the temperature of the fermenting mash as determined by the switching thermometer 24. The time-limit relay which closes its contact to initiate the rotation of the step-by-step switch to the "discharge" position, can be replaced (with the aid of a manually operable change-over switch) by an adjustable contact of a line recorder associated with a device for a continuous, automatic analysis of the alcohol content in the fermenting vat and responsive to a residual alcohol content of between 0.5% and 0.05% based on a comparison of the boiling points of the fermenting liquid and of fermenting liquid from which the alcohol has been removed. A dot recorder associated with a device for an automatic periodic titration of the acetic acid content in the fermentation vat and responsive to a titration valve equivalent to the above-mentioned residual alcohol content, may be used instead.