The use of batch pans is now obsolescent, although still in use in some factories,and sometimes considered to produce the highest quality crumb. The basic process is the same in most modern variants, differences lying in the substitution of continuous processes for batch pans. A typical process of this type involves use of a continuous vacuum concentrator in which concentrated milk from the evaporators is mixed with sugar and cocoa liquor in metered quantities. More water is removed and the resulting paste passes to a continuous mixer/kneader where sucrose crystallizes. The paste is then dried, under vacuum, in a rotating drum dryer. In some cases final drying and additional caramelization take place as the crumb falls down a columm against an counter-flow of hot air.