Lager: Hops fermentation 10-12 days. After fermentation starts, it continues at a slow pace with the beer stored in cellar conditions. When fermentation is completed, the yeast and some additional substances settle out from the beer. Alcohol content would be between 3% & 4%.
Ale: Fermentation time of 6-10 hours whereupon the yeast is skimmed off the surface of the liquor. The yeast is of a different type than that employed in producing the lager beer. No hops are added and the beer is sweet with an alcohol content of 3%.
Porter: A heavy, sweet ale with an alcohol content of 5%, and contains hops.
Stout: Very similar to porter, but with a higher content of hops.
Malt: The beer is sweet and black, is made with a rapid fermentation that leaves a low alcohol content.

The principal constituents of beer are water, alcohol that is generated from the fermentation of the sugar originating in barley malt and an extract of hops that imparts to the beer its particularly bitter taste. The first stage in brewing, which does not necessarily occur in the brewery, is preparation of the barley.

The barley that serves for preparing the malt is usually of a special species that is grown specifically for this purpose. The two types of barley used for this purpose, are the six-rowed barley that grows in the western parts of the USA, Canada, Europe & Australia, and the two-rowed barley that grows in the Far East and in Europe. The malting starts with the soaking of the barley grains in water at 140F-160F; the water is changed several times, till it reaches a moisture content of 45%.

The barley grains germinate in 4-6 days and start sprouting. In the course of germination there appear in the grain enzymes that decompose the starch of the grain into individual molecules. The glucose molecules in the malted grain are now ready for conversion into alcohol and carbon dioxide by means of yeast that is naturally in the air and in the grain. This action of yeast is that which causes grain dough to become chometz =(leavened).

When the malting process is completed the grain is dried in an oven. (Mashing) The drying temperature sets the color of the beer, because high-temperature drying converts a part of the sugar molecules into a dark substance. In addition, the roasting in the oven affects the grain material, adding taste to the beer. In addition concentrated caramel imparts color to the beer, & is produced separately. The sugar molecules are converted into a dark coloring and are added to the standard malt.

The dry grain that is obtained after roasting is rather stable. It can be shipped over long distances and be stored for a year or more. It is therefore possible to have beer that was sown before the previous Passover and can avoid chodosh problems. It depends in how late the current & the previous spring was as far as planting times.

Brewing: The process of brewing beer itself starts actually with the milling of the malt in order to extract the starches and sugars that it contains. The milling is performed in a manner that would minimize damage to the endosperm & the grain's shell. After milling, the flour is crushed, kneaded & cooked in water at different temperatures in the course of which more starch molecules are converted into sugars. Enzymes naturally present in the grain cause this decomposition just as this happens during malting. The cooking causes the sugars and starch parts to dissolve in water. Insoluble parts of the barley grains remain in the water.

Upon termination of cooking the liquid is filtered and the clear part is called WORT.

Fermenting Beer With Yeast: The amount of sugar that is used in fermenting beer is less than that used by making wine. The yeast will therefore remain active after the fermentation. The alcohol content will be between 3-4%.

The beer liquor that is boiled also sterilizes it from bacteria & therefore it is possible to re-use the yeast & it is very often re-used many times over. These yeasts have to be concentrated when reusing, it can be done by centrifuge or by coagulators of gelatin or vegetable coagulators.

The beer industry employees yeast cultures whose coagulating substance is agar agar extracted from algae-a kosher substance, However, it may also contain in minute amounts peptones which are protein derivatives. The peptones may be extracted from plants and from animal proteins.

A part of the carbon dioxide gas that is generated in the course of fermentation is captured in the closed vessel & dissolves in the beer. This will cause foaming and an antifoam agent will be used which needs kosher supervision. There is also a need for additional foam stabilizes needed in the final product. A common stabilizer is propylene glycol alginate, although inherently may be of a kosher origin it may have been produced on equipment that was used for non-kosher esters.

The production of true, clear beer requires the addition of an enzyme. This enzyme may be derived from microorganisms that were grown on a culture bed containing non-kosher nutrients. The yeast within the culture gets its nutrients from the peptones, develops within the vessels that contain the beer liquor. The question what effect that has on the beer as far as kosher is concerned.