Fermentation of grape juice to make wine has been going on in different vats for a number of centuries. A wide range of vessels and containers can be used with differing degrees of success and tastes as required by the winemaker of the time.
Essentially a vat is a vessel used for fermentation. Historically, a fermentation vat was usually a large wooden vessel or individual barels with limited control and sophistication. Over time with the advances in technology and materials, vats developed into larger and larger vessels with greater degrees of process control as wines have been processed on an industrial scale.
Almost any vessel that can be fully cleaned or sterilised can be used for fermentation. Depending on the scale of equipment required, materials such as glass, high density polyethylene, stainless steel and commonly resin lined concrete cube cells. Many producers still use old sterilised wooden vats and quite often oak barrels to give an additional character and flavour to their wine.
The structural design shape and dimensions of the vat can also be critical to the fermentation process. The relationship between the contained ferment volume, height and diameter of the vessel all play a key role in achieving the optimum fermentation whilst finding a good balance between air adsorption during active alcoholic fermentation and the minimisation of acid production prior to racking off. This normally means a fairly cylindrical shape for stainless steel vats and wood, a cube shape for concrete and plastic and even egg shape vessels in certain cases.
Larger vats are today often equipped with in built pump over, refrigeration and temperature control systems to optimise the fermentation process. Some progress has been made over those centuries…