Allergen Cross-Contamination and Bread Trays: Prevention Protocols

The allergen control for trays that leaves the least to chance is a dedicated, clearly marked set for each allergen profile, so trays never cross from one to another; Codex and FDA guidance both recommend dedication where possible, which makes it published best practice, not a legal requirement. Where trays have to be shared, validate the tray cleaning procedure with an allergen-specific test under defined worst-case conditions, then verify at every changeover that the validated procedure was actually followed. Dedicated trays still go through the normal wash; dedication removes changeovers between allergen profiles, not cleaning. A color means one thing in your plant, and that meaning is written down.

How do trays carry allergens from one run to the next?

Through residue that survives a wash and through the stack itself. Crumbs, oil and dough fragments lodge in corners, seams, perforation edges and any worn or scratched patch of the food surface. Flour dust settles on trays waiting in staging. And when empty trays are nested, the bottom of each tray sits on the food surface of the tray below, so a tray that came off an allergen line can transfer residue to one that did not.

The stakes show up in recall data. FDA reports that from September 2009 to September 2014, “about one-third of foods reported to the FDA through the RFR as serious health risks involved undeclared allergens,” and it lists bakery products among the top five food types in allergen-related recalls (FDA, Food Allergies).

For plants under FDA’s preventive controls rule, the requirement is explicit: food allergen controls must include procedures for the “protection of food from allergen cross-contact, including during storage, handling, and use” (21 CFR 117.135). Trays are storage, handling and use in one object.

Should allergen trays be dedicated?

Where you can, yes. The international Codex code of practice on allergen management says containers and utensils used for allergen-containing foods “should, where possible, be dedicated to holding a specific allergen and be marked, tagged, or colour-coded to identify the allergen” (Codex CXC 80-2020, section 5.2.1.1). FDA’s guidance for plants under the preventive controls rule, which is non-binding, says the same for U.S. facilities: “Use dedicated color coded equipment, tools, employee apparel, and utensils for handling allergen-containing ingredients or finished products, when possible” (FDA, Appendix 9: Allergen Cross-Contact Prevention, 2019).

Sources for the table: approach follows Codex CXC 80-2020 section 5.2.1.1 on dedication and scheduling.

Scheduling does part of the work when trays are shared. The same Codex section suggests that “production schedules could be established in some cases whereby products that do not contain allergens are handled at the beginning of the schedule.” Running the allergen-free product first means the shared trays start the day clean for it.

Dedication has a cost, and it is worth stating plainly: more trays in total, more storage, and a sorting step on the return dock. What it buys is fewer allergen changeovers on shared trays, each of which depends on a validated procedure and leaves a verification record. It does not buy an exemption from cleaning: dedicated trays still get their routine wash and its records.

How should color coding work?

Color is fast to read on a busy floor, which is its value. Three rules keep it reliable.

1. One color, one meaning. If purple means “contains milk,” it means that on every tray, dolly, rack, scoop and apron in the building, and it never also means “freezer tray” or “Route 12.” A color reused for a second purpose stops carrying either message. If your trays are also color coded by route for returns (see setting up a tray return and rotation system), route and allergen colors must come from separate, non-overlapping sets, or routes must be marked another way.
2. The scheme is written down. The rules quoted on this page do not assign particular colors to particular allergens; the Codex text asks for trays to be “marked, tagged, or colour-coded,” not for a palette. What matters is that your allergen control plan records which color means what, and that every employee, including temporary staff, learns it before handling trays.
3. Color plus words. Add the allergen name on a label or a molded or stamped mark. Color alone fails in poor light and for staff with color vision deficiency; a printed or molded word gives them a second way to read the tray.

A tray whose color has faded until it no longer reads clearly leaves the allergen program, even if it is otherwise sound.

How do you prove shared trays are clean enough?

With two different activities that are easy to confuse: validation, done at the start and repeated when the conditions it covered change, and verification, done at every changeover.

Validation shows that your written cleaning procedure actually removes the allergen from your trays, under conditions harder than a normal day. It uses a test specific to that allergen. Writing in Food Safety Magazine, Joseph Baumert and Steve Taylor note that qualitative ELISAs, which test for a specific allergen, have “become the most popular test methods within the food industry for use in monitoring allergen controls” (Food Safety Magazine, 2013). The same article sets out how to design the study:

• Worst-case product. “For allergen validation, the focus should be placed upon the component with the highest allergenic load.”
• Hardest spots. “Do not swab only flat, smooth areas. It is important to swab other food contact surfaces, such as crevices, joints, etc., which likely are harder to get clean of all allergen residue.” On a tray, that means inside corners, seams, perforation edges and any worn patch.
• Repetition. “If no allergen residues are detectable during two successive cycles, then in our expert opinion, you have effectively validated the SSOP for this line and this formulation.”

This guide suggests writing three more conditions into the study before you run it: the worst soil the trays meet (residue left for your longest hold before washing, for example), the test kit and its detection limit, and what counts as a pass with that kit. Ask the kit maker how well its swab picks up the allergen from plastic, because a swab that recovers little can pass a dirty tray.

Verification shows that the validated procedure was followed this time. Here the same authors write: “Visual inspections, ATP testing or general protein testing can be used for verification purposes.” Once a procedure is validated for a formulation on a line, they add, further allergen testing “is not needed on each subsequent occasion.” ATP and protein swabs measure general residue; they are not allergen tests, which is why they verify rather than validate. The Codex code adds that cleaning should be verified “through visual observation” and, “where feasible and appropriate, through an analytical testing programme” (section 6.2.1).

Validate again whenever something changes that the original study did not cover. The authors write that the procedure “should be validated again when anything changes,” and their list runs from ingredients, ingredient supplier and formulation to equipment, processing conditions, the cleaning procedure’s own parameters and even the allergen test kit; for trays, a new tray model and a new detergent belong on that list. They also suggest revalidating on a schedule, “perhaps every 6 months” for a formulation made regularly. For everyday washing, see the wash sequence and sanitizer limits for trays.

Which allergens does the plan have to cover?

All nine major food allergens under U.S. law: “milk, eggs, fish, Crustacean shellfish, tree nuts, peanuts, wheat, soybeans, and sesame.” Sesame became the ninth under the FASTER Act, effective January 1, 2023 (FDA).

In a bread plant, two of these shape tray decisions more than the others. Where wheat is in most of what you make, controlling it means protecting the few products that must be free of it, which is the case for dedication. Sesame appears as a topping on some breads and buns, so trays that carry seeded products are a natural candidate for their own set.

Residue type decides the cleaning chemistry. Fat-rich residues, such as those from nut or seed products, need a detergent that removes fat, not only a rinse; your validation study is where you prove the chosen detergent does the job on your trays.

What should you have ready for an audit?

This guide suggests having these ready, whatever scheme you are audited against:

• The allergen control plan, with the tray allocation: which trays serve which lines and how they are marked.
• The written color scheme.
• The tray cleaning procedure for allergen changeovers, with the validation results for each allergen and tray type.
• Verification records from recent changeovers.
• Training records showing that the people who handle trays learned the scheme.
• Any cross-contact event involving trays, and what was done about it.

Walk the floor before the auditor does. If a tray of the wrong color is sitting on a dedicated line, or staff cannot say what a color means, the paperwork will not carry the audit. How allergen tray controls fit into the wider audit is covered in preparing trays for a bakery audit, and where they sit in the food safety plan in placing tray controls in a HACCP plan.

What if you have no allergen tray controls today?

If you have no allergen tray controls today, start from your hazard analysis, not from a ranking of allergens by severity, which this guide does not attempt. Start with the product or line the analysis shows has the most exposure to cross-contact through shared trays, or the strongest need for separation, such as a product labeled free of an allergen the rest of the plant uses, and give it a dedicated, marked set of trays. Then write the color scheme, one color to one meaning, and run a validation study for the cleaning procedure of every tray that still has to be shared.