# A Clean Lab Result Does Not Mean Your Maize Is Safe: Why Maize Millers Must Control Aflatoxin at the Gate and in the Silo

*By Isaac Muthui, CEO, Tamalaki Business Network Ltd. Originally published at* [*factoraerp.com*](https://factoraerp.com/en/blog/aflatoxin-control-checklist-maize-millers-kenya)*.*

Most maize millers can show you an aflatoxin certificate. Far fewer can show you which trucks went into the silo that fed Tuesday's flour, what their moisture was on arrival, and whether anyone tested them before they were mixed with good grain.

That gap matters because aflatoxin does not behave like most quality problems. You cannot see it, smell it or taste it at the levels that break the standard. It is made by moulds that grow on grain that is too wet or damaged, and it survives milling. A small quantity of badly contaminated grain mixed into a large clean lot can push the whole lot over the limit. And when a brand fails in the market, the cost is not one batch: it is a suspended permit, a recall and a brand that customers remember for the wrong reason.

This aflatoxin control checklist is written for maize millers and grain processors in Kenya and East Africa. It does not replace your HACCP plan, your laboratory or KEBS. It sets out eight practical checks that turn aflatoxin from a test result into a controlled process, from the truck at the gate to the flour bag in the warehouse.

## What the standards actually say

**The product limit.** [EAS 44:2011, the East African Standard for milled maize (corn) products](https://law.resource.org/pub/eac/ibr/eas.44.2011.pdf), sets a maximum of **10 ppb total aflatoxin** (B1, B2, G1 and G2 together) and **5 ppb aflatoxin B1**, tested by ISO 16050, with a fumonisin limit of 2 ppm and a moisture maximum of 13% for milled maize products. Clause 7 says milled maize products shall comply with the Codex maximum mycotoxin limits for the commodity, and clause 9 says sampling shall be done in accordance with ISO 13690. Hygiene is to follow EAS 39.

**The code of practice.** [Codex CXC 51-2003, the Code of Practice for the Prevention and Reduction of Mycotoxin Contamination in Cereals](https://qualfood.com/files_ensino/CAC_RCP_51-2003.pdf), is blunt about what is achievable. Complete prevention "is not practically achievable", so "the intermittent presence of certain mycotoxins in cereal grains... is to be expected", and "diligent monitoring" during storage is "imperative" (para 5). It asks processors to use validated methods and sampling plans, to train the people who run them, and to have procedures to handle suspect grain "through segregation, reconditioning, recall or diversion" (para 9b). It says a maximum of 15% moisture is "generally considered" low enough for safe storage (para 30), that a temperature rise of 2-3°C in stored grain may indicate microbial growth or insects (para 39), and that grain removed from storage for transport should be tested at loading or unloading before it goes into storage at the processing plant, "especially when the risk of mycotoxin contamination is high" (para 48).

**Why it matters in Kenya.** Kenya has lived through the worst version of this problem. In 2004, an outbreak of aflatoxin poisoning in Eastern and Central Provinces had reached 317 reported cases and 125 deaths by July, according to the [CDC's investigation report](https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5334a4.htm). It was traced to locally grown maize stored under damp conditions, and 182 of 342 maize samples from markets in the affected districts had more than 20 ppb aflatoxin, the limit Kenyan authorities used at the time. Today's standard for milled maize is half that.

For millers, the regulatory risk is also real. In November 2019, KEBS suspended the permits of five maize flour brands whose aflatoxin levels were above the maximum limit, following market surveillance and reports from the public, and required the manufacturers to recall the products and take corrective action before the suspension could be lifted, the [Daily Nation reported](https://nation.africa/kenya/news/kebs-bans-5-maize-flour-brands-over-high-aflatoxin-levels-221572). A few days earlier, KEBS had suspended seven peanut butter brands. Groundnuts and other nuts carry the same risk; check the standard for your product.

## Why a lab certificate is not enough

A lab result describes a sample. If the sample was taken from the top of one bag, it describes the top of one bag. Aflatoxin is not spread evenly through a lot; it is concentrated in a small number of mouldy or damaged kernels. That is why EAS 44 points to a sampling standard, and why Codex keeps repeating that the sampling plan matters as much as the test.

A certificate from a supplier also describes grain at a moment in the past. Grain that was safe at 13% moisture in the supplier's store can pick up moisture on an uncovered truck in the long rains and keep growing mould in your silo. The control is not the paper. It is what you do with every lot, every day, from intake to dispatch.

## The 8-step aflatoxin control checklist

### 1\. Approve suppliers and agree an intake specification

- Keep an approved supplier list for grain, including aggregators and traders, not only large farms. Record who supplied each lot, from which area and season.
- Agree in writing the intake specification you will apply: maximum moisture, maximum aflatoxin on your rapid test, limits for mouldy, discoloured, broken and insect-damaged kernels, and what happens to a rejected load.
- Ask for the supplier's own test results where they exist, but treat them as information, not as release. Our [supplier intake checklist](https://factoraerp.com/en/blog/supplier-intake-checklist-food-manufacturers-kenya) covers the wider approval routine.

### 2\. Inspect every truck before it is tipped

- Check the vehicle before unloading: dry, covered, free of old grain, dust, visible mould, musty smell and insects, as Codex expects of transport containers (para 44).
- Look at the grain: mouldy, discoloured or shrivelled kernels, wet patches, caking and heating are reasons to stop and sample before anything is tipped into a silo or onto a heap.
- Give each truck a lot number at the gate, before it is mixed with anything. Once it is in the silo, it can no longer be rejected on its own.

### 3\. Sample properly, not conveniently

- Take incremental samples from many points of the load, top, middle and bottom, or from the moving stream, according to your documented sampling plan based on ISO 13690. A single handful from the tailgate is not a sample.
- Combine, mix and reduce the sample in a consistent way, and keep part of it, labelled with the lot number, as a retained sample.
- Train and assess the people who sample. Codex says sampling plans and tests need "adequate resources and training" to give accurate results.

### 4\. Test moisture and aflatoxin at intake, and record both

- Measure moisture on every lot with a meter that is checked and calibrated, as Codex expects of moisture equipment (para 23). See our [calibration checklist](https://factoraerp.com/en/blog/calibration-checklist-food-factories-kenya).
- Run a validated rapid aflatoxin test on each lot, or on the lots your risk assessment flags, such as wet-season deliveries or new suppliers. Confirm a planned share of lots, and any doubtful result, with an accredited laboratory using a reference method.
- Record the reading, the method, the kit lot, the tester and the time against the truck's lot number. A result that is not tied to a lot cannot protect you later.

### 5\. Segregate, hold or reject before mixing

- Decide the outcome before the grain moves: accept, accept for drying and cleaning, hold pending lab confirmation, or reject. Write down who can make each decision.
- Keep held lots physically separate and clearly marked. Codex warns that small quantities of highly contaminated grain "can greatly increase mycotoxin levels" in otherwise good grain (para 39), so never blend a failed lot down to meet the limit.
- Treat a hold as a real stock status, as in our [QA hold checklist](https://factoraerp.com/en/blog/qa-hold-checklist-before-batch-leaves-warehouse-kenya), so held grain cannot be issued to production by mistake.

### 6\. Dry, clean and sort before storage and milling

- Grain above your storage moisture limit should be dried promptly, not piled or left in bags for days. Codex says high-moisture grain should not be heaped for more than a few hours before drying (para 28).
- Clean and sort to remove broken, immature, mouldy and discoloured kernels, dust and foreign matter. Codex calls sorting and cleaning "effective processes" to reduce mycotoxin content (para 47), and our [foreign body control checklist](https://factoraerp.com/en/blog/foreign-body-control-checklist-food-factories-kenya) covers the screens and magnets on the same line.
- Remember that the cleanings, hulls and bran carry more aflatoxin than the endosperm (Codex para 49 and 50). Control where screenings and bran go, and test them if they are sold as food or feed.

### 7\. Monitor storage every week

- Store grain in dry, ventilated, rain-proof structures, with bags clean, dry and stacked on pallets off the floor (Codex para 34 to 36).
- Record grain temperature and moisture on a schedule. A rise of 2-3°C may be the first sign of mould or insects (para 39). Look for condensation, leaks, wet spots and insect activity, and act on what you find.
- Clean silos and stores before refilling, rotate stock first in, first out, and keep rodents and insects out with a proper [pest control programme](https://factoraerp.com/en/blog/pest-control-checklist-food-factories-kenya). Milled products stored for long periods can also grow mould (para 51), so the same discipline applies to flour in the warehouse.

### 8\. Test the finished product and link it to its grain

- Test finished flour against EAS 44 on a defined frequency, and more often in high-risk seasons or after a new supplier, with the result recorded against the production batch.
- Keep the link from flour batch back to silo, intake lots and suppliers. If a market sample fails, you need to know within hours which batches share the same grain, which customers received them, and which lots are still in store. That is a traceability exercise, and a [mock recall](https://factoraerp.com/en/blog/how-to-run-a-mock-recall-food-traceability-kenya) is the way to prove you can do it.
- Keep retained samples of each batch for at least the shelf life, so a complaint can be checked against what actually left the plant. Our [customer complaint handling checklist](https://factoraerp.com/en/blog/customer-complaint-handling-checklist-food-factories-kenya) covers what to do when one comes in.

## The daily aflatoxin record

At the end of each day, a miller should be able to answer five questions from records, not memory:

1. Which grain lots were received, from whom, and what were their moisture and aflatoxin results?
2. Which lots were rejected, held, dried or cleaned, and who decided?
3. Which silo or store does each accepted lot sit in, and what are its latest temperature and moisture readings?
4. Which intake lots went into each flour batch?
5. Which finished batches were tested, with what result, and where have they been dispatched?

If any answer depends on one person's notebook, that is the gap to close first.

## Habits that make aflatoxin control stick

- **Make rejection safe.** The intake clerk who turns away a wet truck from an important supplier needs management support, written criteria and a clear escalation path.
- **Watch the season.** Codex notes that contamination varies widely from year to year with the weather. Increase testing frequency during and after the long and short rains and when grain comes from areas with a poor harvest.
- **Trend the results.** Plot aflatoxin and moisture by supplier and by month. A supplier who is always just under the limit deserves more attention than one who failed once.
- **Close the loop with suppliers.** Share results and rejection reasons, and help good suppliers dry and store better. Codex places much of the prevention on farm and in storage, long before grain reaches the mill.

Aflatoxin control connects to the rest of your quality system: [stock count reconciliation](https://factoraerp.com/en/blog/stock-count-reconciliation-checklist-food-factories-kenya) keeps silo and warehouse balances honest, [FEFO and expiry tracking](https://factoraerp.com/en/blog/reduce-expiry-spoilage-losses-fefo-batch-expiry-tracking) keeps old flour from sitting too long, [cleaning and sanitation](https://factoraerp.com/en/blog/cleaning-sanitation-checklist-food-factories-kenya) removes the dust and residues that harbour mould spores, and [batch costing and yield tracking](https://factoraerp.com/en/blog/batch-costing-yield-tracking-agro-processors-kenya) shows what rejected and downgraded grain really costs you.

## Where an ERP helps

A small mill can run this on paper and a well-kept register. It gets harder with many suppliers, several silos and two shifts, because the question after a failed market sample is "which flour batches used grain from these trucks, and where did they go?", and the answer is spread across the gate book, the lab sheet, the silo log and the dispatch notes.

FactoraERP tracks production batches and lots, stock status including QA holds, and non-conformance records with owners and closing dates. A failed intake result or a heating silo can be logged as a non-conformance with an owner and a corrective action, the affected lots placed on hold so they cannot be issued, and the batches that used them traced for a recall decision. That puts the aflatoxin record next to the stock and production record instead of in a separate file. See [factoraerp.com](https://factoraerp.com).

## Free download: eTIMS readiness checklist for factories

Kenyan manufacturers increasingly need their operational records, stock records and invoices to tell one consistent story. If you want a free **eTIMS readiness checklist for factories**, sign up for the FactoraERP Insights newsletter at <https://isaacmuthui.substack.com>. You will get practical operations notes for food and agro manufacturers. No spam; unsubscribe anytime. For background, see our guide to [eTIMS for food and agro manufacturers](https://factoraerp.com/en/blog/etims-for-food-agro-manufacturers-kenya).

## FAQ

**What should an aflatoxin control checklist for a maize mill include?**\
Supplier approval and an intake specification, inspection of every truck, a documented sampling plan, moisture and aflatoxin testing at intake recorded against each lot, segregation and holds before mixing, drying, cleaning and sorting, weekly storage monitoring, and finished product testing linked back to grain lots.

**What is the aflatoxin limit for maize flour in East Africa?**\
EAS 44:2011 for milled maize products sets a maximum of 10 ppb total aflatoxin (B1, B2, G1 and G2) and 5 ppb aflatoxin B1, tested by ISO 16050. Always check the current version of the standard and any KEBS requirements that apply to your product.

**What moisture level is safe for storing maize?**\
Codex CXC 51-2003 says a maximum of 15% moisture is generally considered low enough to prevent further fungal growth in storage, while EAS 44 sets 13% as the maximum for milled maize products. Many plants set a stricter intake limit; base yours on your grain, storage period and conditions.

**Can cleaning and sorting remove aflatoxin?**\
They reduce it by removing mouldy, damaged and broken kernels, dust and foreign matter, but Codex notes that kernels with symptomless infections cannot be removed by standard cleaning. Cleanings and bran fractions carry higher levels and must be controlled.

**Can a contaminated lot be blended with clean maize to meet the limit?**\
Do not do it. Codex warns that small quantities of highly contaminated grain can greatly increase levels in otherwise good grain. Hold the lot and decide on rejection, reconditioning or diversion under a documented procedure, with your regulator's requirements in mind.

**Are rapid aflatoxin test kits enough?**\
Validated rapid tests are useful for intake decisions, but they depend on a good sample and a trained tester. Confirm a planned share of lots and any doubtful result with an accredited laboratory using a reference method.

---

*Isaac Muthui, CEO, Tamalaki Business Network Ltd*