Protein soil
A soil class rather than a stain. Alkali removes it, heat welds it on, and almost every household mistake with it is a temperature mistake.
In detail
Protein soil is the class that milk, egg, blood, gravy, meat juices and skin all belong to, and classifying it that way is more useful than treating each as its own problem. A public-health cleaning guideline for dairy plants sets out the removal chemistry plainly: protein is removed by alkaline solutions, and it is described as difficult to clean once heated. Two practical rules follow and they are the opposite of instinct. Hot water is the wrong first move, because heat denatures protein and binds it to the surface — the same industrial protocol runs its PRE-RINSE at a modest temperature specifically to 'prevent protein adherence' before any chemistry is applied. And alkali is the tool, which is why laundry products carry protease and why washing-up liquid alone struggles with baked egg. The household version of the plant's rule is simply this: get protein off cold, before anything hot touches it.
What works
Sodium carbonate is effective against Protein soil Supported
Alkali is the tool for protein. Not heat, and not a stronger surfactant.
Detergent is effective against Protein soil Established practitioner practice
Why
- Protein soil is explained by Heat-set stains
- Protein soil is explained by Protein denaturation
Sources for this page
Sources
Dairy Processing Plants: Guidelines for the Cleaning of Dairy Plant Processing Equipment
British Columbia Centre for Disease Control (BCCDC), Canada · Government or regulator
Relied on for: That Table 3 classifies milk soil into lactose removed by water, fat removed by surface active solutions, protein removed by alkaline solutions and mineral salts removed by acid solutions, and that every one of the four becomes more difficult to clean after heating. (states this directly)
Verification: a person has read the passage relied on.
Read on — Part II: 'Cleaning Steps' (Table 1), 'Factors Affecting Cleaning', 'Soil Characteristics' (Table 3) and 'Water Impurities' (Table 4). Supports the claim as stated. Supplies a soil classification by removal chemistry, the first numeric water-impurity thresholds in the register, and a professional cleaning protocol with a temperature for every step.
Last reviewed by a person on .