Are you asking yourself the question what is the limit of detection needed. People ask me how low is low enough. When you are cleaning to remove allergens you need to know when you are done cleaning. The answer like many in food safety is, it depends. A thorough review of the risks is an important starting point.
You are trying to ensure that you do not have enough allergen left on your equipment that would carry over to a new production run of a product that does not have that allergen. This could cause an allergic response in an unwary consumer.
The method of confirming the cleaning is adequate varies. Some document on a checklist that the surfaces were visually clean. Some swab cleaned surfaces on some frequency and test the swab. Others capture part of the following production run or a rinse solution and test that material. The tests are done using various test methods to determine if the target allergen is present either directly through antibody/dna testing or indirectly through general protein or ATP testing.
So how low is low enough will depend on what your risk is of a allergen cross-contact causing a consumer to have a response. There is work by the FDA and WHO on creating guidance to help as well as some other industry guidelines that may be specific to the products you make.
