Lesson 2 - Cleaning Systems and Control

There are different types of disinfectants for use in different areas of the plant. They are formulated differently to minimise the negative effects that they might have on the finished product.

CIP sanitisers

Commonly used CIP disinfectants are peroxyacetic acid (PAA) and hydrogen peroxide based. PAA is made from the blending of acetic acid and hydrogen peroxide in the presence of a stabilising agent. When used, PAA breaks down into hydrogen peroxide and acetic acid, which will further degrade into water, oxygen and carbon dioxide. Hydrogen peroxide on its own will breakdown into water and oxygen.

Because PAA based sanitisers are oxidising, they can affect flavour stability of beer if used at too high a concentration or a large volume is left in a vessel. The implication is that if the sanitiser is rinsed out of the vessel, the rinse water should itself be sanitised (such as by using chlorine dioxide). 

Disinfectants for equipment baths

Iodophors were historically used in sanitiser baths because their presence could be detected by the brownish-red colour. Iodophors combine elemental iodine with surface-active compounds in an acidic solution. They can taint the product when not handled properly. For this reason to mitigate PAA based sanitisers are usually used today. More modern disinfectants e.g. triamine based or fatty acids in an acidic base are also used. 

Environmental sanitisers (detergents / disinfectants)

Environmental sanitisers are generally high foam producing detergents used for sanitising floors, walls, external surfaces of tanks and pipes, and the cleaning of drains. Often they are foam negative so are not used in soak baths or for beer contact surfaces.

For these sanitisers to work effectively, they must be able to cling to the surface to allow for extended contact time. When rinsed off the walls, they must be easily removed. Because they are not for beer surface cleaning, there is a wider choice of ingredients that can be used.

Quaternary ammonium compound (QAC) sanitisers work by surface action. The QAC formulations contain additional non-ionic surfactants, e.g. ethoxylated fatty alcohols, to boost foaming properties of the product. So that microorganisms do not develop a resistance to some sanitisers, different types should be used over specific periods of time.

Sanitisers for drains

The most popular sanitiser for drains is sodium hypochlorite solution that has been diluted to release about 5% available chlorine during use. These must be kept separate from stainless steel equipment; the free chlorine settles on the moist surface causing pitting corrosion under certain conditions, e.g. high chloride concentration or high temperatures. Many modern brewery installations use stainless steel drains which may suggest that chlorine could be an unsuitable sanitiser in this case.

Water disinfectants

Chlorine dioxide has gained popularity as an effective, safe to use disinfectant. It is effective at low concentration against a wide spectrum of microorganisms. At higher concentrations, it is also effective in removing biofilms. As it does not chlorinate, there is no risk of forming trihalomethanes (THM) when organic compounds are present.

Chlorine dioxide can be used for the disinfection of many areas, e.g. water disinfection, post or final rinse disinfectant, and as a biocide for cooling tower and pasteurisers.

It is corrosive to stainless steel however, and its concentration needs to be carefully controlled.

Occasionally chlorine dioxide is also used as a brewery plant sanitiser at 2 to 5 mg/L, but needs to be rinsed off with sterile water afterwards.

Hot water as a disinfectant

Hot water of 80 °C or higher is sometimes used as a disinfectant in the brewery as an alternative to PAA. For pipework cleaning a hot caustic clean of 30 minutes is followed by a hot water sanitisation of 5-20 minutes. Hot water is also used to sanitise the beer filter and packaging fillers.