Fermentation requires several things - sugar within certain concentration ranges, healthy live yeast, proper temperatures and nutrients to allow the yeast cells to increase in number and remain healthy throughout the fermentation process. A good, controlled fermentation with complete conversion of the sugars to alcohol but producing no bad or "off' flavors, requires a few more:
• Good sanitation and cleanliness
• Selection of the best yeast variety
• Using a large quantity of that yeast
• Proper fermenter geometry
• Fairly precise control and management of temperature, pH and oxygen levels
Don't despair, though - in normal hobbyist quantities, these are all fairly easy to arrange.
In many countries, home beer, mead and wine making are well established hobbies, and many stores provide a wide variety of materiel and equipment to carry out fermentation. Let's take a look at this equipment and consider how it may be used for our purposes. Later on, we'll examine the possibilities for higher volume and more intensive fermentation.
The single most common fermentation vessel in use is a glass carboy sized to contain 12 to 25 liters (3 to 6 US gallons) of fluid. In the USA, the five gallon carboy is the overwhelming favorite, because it's cheap, conveniently sized, and readily available. The advantages of the glass carboy are: it's clear (which means progress can be followed without opening it), is easy to sanitize, and has a small opening in which it's easy to fit an airlock for oxygen control. The most obvious disadvantage is that it is breakable - both by physical impact and by exposure to extremes of temperature (don't sterilize with boiling water!) The carboy also allows a single-stage fermentation to be performed when there are no solids that need to be removed part way through the process (grains, grape skins, etc).
The second most common fermentation vessel is a plastic bucket or trash container made out of food grade polyethylene or polypropylene. These range in size from 20 to 80 liters (5 to 20 US gallons), and are more commonly used in wine making than in beer or mead. The advantages of the plastic containers include the facts that they are open - materials can be easily added to or taken out of them -and that they are unbreakable. The disadvantages are: they are harder to sanitize than glass, especially if the plastic is scratched, oxygen diffusion through the plastic may limit their safe use to short fermentations, and they can also absorb bad odors or flavors and later impart these to the fermenting ambrosia.
Both plastic buckets and trash containers have reasonable geometry for unstirred fermentation - one and a half to two times taller than they are wide. This allows the fermenting fluid to circulate due to the action of the CO2 produced. Shallow, wide fermenters can be successfully used, but generally need some sort of mechanical stirring.
A fermentation started in an open container (even if fitted with a loose lid) should be finished in a second, closed container - a carboy, barrel, or stainless steel tank, to allow control of oxygen levels.
Accessory equipment needed to do a good job of managing fermentation includes accurate thermometers, hydrometers, pH test paper, airlocks, hoses for siphoning liquid from vessel to vessel, funnels, stoppers and cleaning supplies. These are the basic items and can be purchased very cheaply. For the enthusiast, more sophisticated equipment is available from hobbyist shops and specialized manufacturers. Countless resources are available, including many good books, catalogs, websites and magazines that detail how to use all of this gear to maximum advantage.
Many of the precise procedures used will depend upon the material being fermented, and the flavors desired in the final product. In this book, we're mainly concerned with the basics of fermentation and don't pretend to offer advice on how to produce fine beer, wine or mead. If your interest is sparked by that absorbing pastime, then you'll find dozens of excellent books covering these subjects in depth.
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