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.
Detergents and Disinfectants
Detergents are a blend of chemicals, added together to solubilise soil and remove it from the surface. This ensures that it does not re-deposit itself back onto the cleaned surface. Disinfectants are formulated to kill microbes and bring the microorganism load to an acceptable level.
Soil removal by detergents
Soil is removed from surfaces in the following sequence:
- The cleaning solution is transported to the soil and penetrates into it, causing wetting.
- Chemical and physical solubilisation occurs between the water ions, soil, and cleaning agent, which breaks up the soil into particles.
- The soil is removed and transferred into the cleaning solution via dispersion and emulsification.
- The soil is removed from the area being cleaned in the cleaning solution. It is prevented from re-depositing by stabilising agents in the cleaning solution itself.
Disinfectants
Disinfectants are intended to be used on already clean surfaces, reducing the microorganism load to levels that are acceptable to the brewer. This is done by creating the conditions of temperature, pH, chemical or surface activity that will kill microorganisms. The efficacy of the disinfectant depends on the microbial load, accessibility, physical conditions, disinfectant concentration, and contact time. Disinfectants are in an acidic medium when peracetic acid or hydrogen peroxide are used, and in an alkaline medium when halogens such as chlorine are used.
Detergents
Detergents are used to clean brewing surfaces and are formulated from a baseline of acids or alkalis. Typical acids are nitric and phosphoric, which are effective at removing inorganic soil. Alkaline detergents incorporate sodium hydroxide (caustic soda) and occasionally potassium hydroxide, which are good at removing organic soil.
The requirements for an ideal detergent can be listed as follows:
- Completely soluble in water
- Adequate wetting properties
- Able to disperse and suspend particles
- Able to emulsify fats
- High sequestering activity, which we will define shortly
- Low foaming
- Non-corrosive
- High rinsability
- Biodegradable
- Non-toxic
The baseline acids and alkalis do not satisfy these properties on their own, so commercial detergents are usually formulated by the addition of complementary agents.