Fermentation rooms

Fermentation. The term fermentation arose from the misconception that black tea production is a microbial process (73). The conversion of green leaf to black tea was recognized as an oxidative process initiated by tea—enzyme catalysis circa 1901 (74). The process, which starts at the onset of maceration, is allowed to continue under ambient conditions. Leaf temperature is maintained at less than 25—30°C as lower (15—25°C) temperatures improve flavor (75). Temperature control and air diffusion are faciUtated by distributing macerated leaf in layers 5—8 cm deep on the factory floor, but more often on racked trays in a fermentation room maintained at a high rh and at the lowest feasible temperature. Depending on the nature of the leaf, the maceration techniques, the ambient temperature, and the style of tea desired, the fermentation time can vary from 45 min to 3 h. More highly controlled systems depend on the timed conveyance of macerated leaf on mesh belts for forced-air circulation. If the system is enclosed, humidity and temperature control are improved (76). 

Treatment of the Wort. The hot wort produced in the brewhouse cannot be transferred directly to the fermenting room. If natural hops are used they must be separated by a hop strainer as shown in Figure 8. During boiling, protein—tannin complexes are precipitated in the form of warm sludge. 

GUr-probe, /. fermentation sample or t t. -produkt, n. fermentation product, -prozess, m. fermentation (process), -raum, m. fermenting room. 

The oxidative process actually starts with the onset of maceration of withered leaf. At the end of the rolling process leaf is allowed to oxidize in 5 to 8 cm beds on trays in another fermentation room. It is desirable to keep temperatures below 30°C. Oxidation at 15 to 20°C is said to improve flavor.79 High humidity prevents surface drying and consequent retardation of oxidation. 

A small diameter pipe 32 m long runs from the fermentation room of a winery to the bottle filling cellar. Sometimes red wine is pumped through the pipe, sometimes white, and whenever the switch is made from one to the other a small amount of house blend rose is produced (8 bottles). Because of some construction in the winery the pipeline length will have to be increased to 50 m. For the same flow rate of wine, how many bottles of rose may we now expect to get each time we switch the flow ... 

Fermentation Curves. Fermentation curves are an index of the general well being of the fermentation processes taking place in the fermentation room. Abnormal yeast populations or improper temperature control often can be seen first in the plotted data of sugar content vs. time during fermentation. 

For white wine production, the grapes usually were not stemmed. The crushed grapes were left for six to ten hours before the free-run (separated) juice was drawn off. The pomace was then pressed and the pressed pomace was washed as with red pomace. The fermentation of white musts was done in 2/3-full oak casks. The fermentation was watched daily. The yeast foam was removed. By the sixth day, the fermentation had slowed down sufficiently to then use a fermenting bung. The Italians often use a bag of sand, which they place over the bung-hole. He recommended fermenting room temperatures of 21°-27° C and cellar temperatures of 15.6°-21° C, preferring 15.6° C after the first year. 

Carbon dioxide evolution is not dangerous in enclosed vessels (except for those who enter them) whereas it can be a continual hazard in those fermentation rooms having both open vessels and poor air circulation. About 4 % of carbon dioxide in air by volume can be a danger, even for short periods and legislation may limit levels in some countries to below 0-5 %. 

---