Excessive Foam Formation during CIP of Dairy Plant

Caustic soda is the most widely used chemical for cleaning in place. During operation, caustic soda reacts with fats and proteins. This splits them into smaller molecules and creating foaming compounds (saponification process). Foaming compounds reduce the surface tension of water, increasing the cleansing ability.

Basic (general) Facts about Foam Formation:

1) The pure liquid caustic solution do not foam

2) Presence of surface active agent (also called surfactant) is needed to produce foam

3) Surfactants are amphi-polar, composed of a non-polar hydrophobic tail and a polar hydrophilic head. They reduce water surface tension and thereby emulsify the fats

4) Foam is created when air is mixed in water with its surface tension is reduced, producing bubbles. Many substances, besides soap and detergents, will reduce surface tension

5) Foams are essentially unstable and tend to collapse, separating air and liquid

High organic loads during the caustic phase of the CIP cleaning causes the saponification conditions that then result in excessive foaming. Thus excessive foaming is often associated with product contamination though other factors such as air entrainment via leaking pump seals or the use of totally softened water should also be checked as possibilities.

Foam, if not held under control will decrease cleaning performance, as it is difficult to rinse, causes cavitation in pumps as a result of air introduction into the lines, reduces the efficiency of the cleaning agent. Foaming also causes carry-over and can be very dangerous because hot and concentrated solution are used. It will cause the tank (if the CIP liquid is recovered) or drain pipe (if drained to wastewater treatment) to overfill / overflow

 

So, how do we avoid such a situation ? My recommendations are as follows:

1) Completely drain out the product inside the lines and equipment - recover and use up all the product inside the pipelines and tanks prior to cleaning. Any leftover product forms the soiling on the system whose fats and protein content cause the foaming reaction. Pipe pigging may be considered to empty out long lengths of pipelines. Savings from the product recovered and reduction in waste water load can justify its investment
2) Ensure correct CIP operation during the pre-rinse phase - the right turbulence / velocity must be flowing through all parts of the system being cleaned with sufficient time to remove the majority of the soil. This also saves on the chemical consumption for the succeeding phases
3) Review equipment and pipelines installation design for proper drainage slopes - no liquid should be left stagnant on the lines when the equipment stops
4) Defoamers - added to cleaning solutions. Non-ionic surface active agents become effective defoamers at temperatures where they are no longer soluble in water. Silicones although are good defoamers, are typically avoided, as most have a tendency to adhere to surfaces
5) Use of other cleaning agents - may substantially increase the cost as other chemicals are much more expensive than caustic