Beer is filtered to remove yeast and other solids eg hops an

Beer is filtered to remove yeast and other solids (e.g. hops and malt particles), and make it clear. Filter aids such as diatomaceous earth are sometimes added to allow more beer to be filtered per batch and to speed the process.

(a) Explain the advantages and disadvantages of using a Vmax versus a Pmax strategy in the filtration of beer.

(b) Explain the difference in procedure between the Vmax (constant pressure) test and the Pmax (constant flow rate) tests. What experimental set-up would you need to preform each test? What would you measure?

Solution

(a) Vmax refers to the maximum volume of beer that can pass through the mesh without plugging in a unit of time. This strategy is useful in determining the size of filter, which is very important in determining the efficiency of method. It provides filtration by passage of fluid at desired flow rate with minimum area.

Vax is used for surface filters whereas P max is used for in depth filters. Due to indepth structure Pmax filters provide much more surface area required for dirt loading, dirt carrying and still filtering.

(b) The basic procedure for the filtration requires a number of cartridges in sequence through which the filtrate passes on. Each filter makes the liquid less thick for next filter. Selection of appropriate filter cartridge increases life of the next cartridges in sequence and reduces total filtration cost. Because many types of substrates and filters are there, the selection of filter is very important. Hence there are Vmax (that applies constant pressure) and Pmax (that maintains constant flow) techniques.

In substrates like beer where the particle size is medium to large, plugging profiling is done for the particles passing with load. Sometimes Vmax constant pressure technique is done to select the size of filters. Vmax is fast reliable and versatile to design complete cartridge train in very short time. A basic model is developed to predict the execution of large scale model. Though Vmax is generally adopted, the Pmax ( a constant flow technique) provides faster and more accurate results in selecting and sizing depth filters.