Lesson 2 - Cleaning Systems and Control
This lesson explores the concepts of hygienic design and the Cleaning-in-Place (CIP) systems in the brewery. We examine the nature of soils, the chemicals used to remove them and how we can validate cleaning effectiveness. We also consider the optimisation of modern cleaning systems within the brewery.
Caustic Soda
Caustic soda, lye, sodium hydroxide or just caustic, is a strong alkali that decomposes proteins at room temperature. It is the detergent of choice for dissolving organic soiling. It is particularly soluble in water and can be supplied as a bulk liquid concentration of up to 50% by weight. Caustic is delivered in pre-formulated liquid form to allow it to be pumped and diluted up to a typical working strength of 1-3% w/v in brewery CIP systems.
Used on its own caustic lacks wettability and is difficult to rinse off surfaces. It is also prone to foaming in CIP sets due to saponification (soap forming) reactions with lipids in soil.
To increase effectiveness, sequestrants and chelants are added to the raw caustic by the detergent supplier.
Caustic soda is sometimes supplemented with oxidising agents such as hypochlorite and hydrogen peroxide. These can be useful to assist in the removal of burnt-on deposits in the wort kettle and organic deposits in fermentation vessels. The use of chlorinated caustic should be restricted due to the corrosive nature of these formulations, which in the case of chlorinated caustic, should not exceed 500 mg/L and 50 °C.
Caustic is used at ambient temperatures, as well as heated in brewery environments according to the equipment being cleaned. A big risk in CO2 environments is that rapid CO2 absorption and reaction with sodium hydroxide can cause large vessels to suck in or implode from the resultant vacuum. The resulting product, sodium carbonate, is only around 10% of the detergency of caustic.