- In particular, for plants that produce several products on the same line, allergenic protein residues may remain on equipment surfaces after production and cleaning. If they are not detected in time, the risk of allergen cross-contamination can affect product quality and consumer safety.

- So which locations should be prioritised for allergen sampling? Below are the 5 important areas that the QA/QC department should include in the surface allergen testing.

1. Surfaces in direct contact with food

- This is the group of locations that should be given top priority when building an allergen sampling plan. Surfaces in direct contact with product during production may retain allergenic protein if the cleaning process does not completely remove residues. Some locations that often need to be tested are:

  • Conveyors in direct contact with food.
  • Raw material chutes.
  • Feed hoppers.
  • Mixing tanks.
  • Agitator blades.
  • Moulds and trays in contact with product.
  • Knives, cutting tools or processing equipment.
  • Interior surfaces of processing equipment.

- For example, if a plant has just produced a product containing milk, egg, soy or peanut, then switches to a product that does not contain these ingredients, verifying cleaning effectiveness with allergen testing can help detect the risk of residues before the next production run starts.

Why is this location important?

- Testing surfaces after cleaning helps the business answer an important question: “Has the line really been allergen-free before running the next product?”

- This is also one of the important applications of surface allergen testing in the plant sanitation programme.

2. Hard-to-clean points on the production line

- Not every location on the equipment is equally easy to clean. Areas with complex structures, narrow gaps or hidden corners often risk retaining raw material residues after production.

- Locations that should be included in the sampling programme are:

  • Joints between equipment parts.
  • Gaskets and seals.
  • Valves and pipes.
  • Hidden corners inside the machine.
  • Conveyor belt joints.
  • Areas underneath or behind the equipment.
  • Dead legs in the CIP system.

- These are locations that can be regarded as “worst-case locations” in a sanitation validation programme. Instead of sampling only easily accessible surfaces, QA/QC should identify the locations most likely to have allergen residues for testing.

3. Tools and equipment shared between multiple products

- Another source of risk that is often overlooked is the tools used for multiple product lines. For example:

  • Raw material scoops.
  • Containers.
  • Trays.
  • Spoons, measuring scoops.
  • Knives and cutting tools.
  • Tongs or gripping tools.
  • Weighing equipment and areas in contact with raw material.

- If a tool that has been in contact with allergen-containing raw material is reused for another product without being cleaned properly, cross-contamination can occur.

- Therefore, allergen sampling on shared tools is a useful step to evaluate how effective the cleaning process actually is.

4. Transition areas between production steps

- Transition points between the raw material, processing and packaging areas also need attention when setting up an allergen monitoring plan. For example:

Raw material store → weighing area → blending area → processing → packaging

- In these areas, allergens can be spread through:

  • Spilled raw material.
  • Raw material dust.
  • Transport equipment.
  • Carts.
  • Gloves.
  • Footwear or protective clothing.
  • Packaging and items used in production.

- Not all locations need to be sampled at the same frequency. The plant should base its sampling programme on allergen cross-contamination risk assessment.

5. Surfaces after the cleaning process is completed

- This is a particularly important time to carry out surface allergen testing. After an allergen-containing production run ends and the cleaning process is complete, QA/QC can sample at previously identified locations to evaluate cleaning effectiveness.

- A basic procedure can be set up as follows:

Produce allergen-containing product → clean the line → take surface samples → test for allergens → evaluate results → allow production of the next product

- If the results show that allergen residues are still present, the business can take appropriate actions such as:

  • Re-clean the area.
  • Identify the cause of the residues.
  • Re-check the cleaning process.
  • Increase the testing frequency.
  • Re-evaluate the sampling points.
  • Retrain staff if necessary.

- As a result, the test results are not only “pass/fail” but also become data to improve the line sanitation programme.

How many locations are enough for allergen sampling?

- There is no fixed number that applies to every plant. The number and sampling locations should be determined based on the risk level, for example:

  • The type of allergen used.
  • The type of product produced.
  • The line design.
  • The degree of contact between raw material and equipment.
  • The cleanability of the equipment.
  • The frequency of product changeover.
  • The history of test results.
  • The plant's cleaning/CIP process.

- A practical approach is to build an allergen sampling point map for each production line. For example:

- This approach helps QA/QC focus resources on high-risk locations instead of sampling everywhere.

What does rapid allergen testing bring to the plant?

- One of the challenges of an allergen control programme is that the business needs to know the effectiveness of cleaning at the time of testing, rather than relying only on visual inspection. Rapid allergen test methods can support on-site testing of surfaces after cleaning.

- The process can usually be implemented as follows:

Take surface samples → perform the test → read the results → decide to re-clean or allow production

- The advantage of on-site testing is that the QA/QC department can quickly identify failures and deal with them before the line switches to producing the next product.

- In particular, this method is suitable for establishing line sanitation monitoring by production shift or at control points identified on the basis of risk assessment.

5 locations to prioritise in the allergen sampling programme

In summary, when building an allergen control programme in a food plant, QA/QC should prioritise:

1. Surfaces in direct contact with food → Direct risk of allergen residues on the line.

2. Gaps, gaskets, hidden corners and hard-to-clean points → Can retain residues after the cleaning process.

3. Shared tools → Risk of carrying allergens from one product to another.

4. Transition points between process steps → Cross-contamination can occur through raw material, tools or people.

5. Surfaces after cleaning is completed → Helps confirm the effectiveness of the cleaning process before running the next product.

Conclusion

- Allergen sampling should not be done at random but should be based on risk assessment and the practical characteristics of each production line.

- Correctly identifying high-risk locations, combined with surface allergen testing and a line sanitation monitoring programme, helps the business proactively detect the risk of allergen residues and improve the cross-contamination control process.

- For plants producing multiple products on the same line, building a sampling point map and using rapid on-site allergen testing can become a useful tool in the sanitation validation and food safety control programme.

- Are you looking to build an allergen sampling programme for a food plant? First identify the allergens in use, the production lines and the hard-to-clean points so that you can choose suitable sampling locations.

- Refer to the rapid allergy test kits we supply here.