Nitrogen storage and aflatoxin control in hazelnuts

The storage service we use for in-shell hazelnuts includes a nitrogen atmosphere. Explaining its role requires discussing both its benefits and its limits. Storage helps preserve the result of harvesting and drying; it does not erase a product's history. This article complements our guides to aflatoxin formation and harvesting and drying from the perspective of storage and procurement.

Nitrogen changes the storage atmosphere

Nitrogen displaces oxygen-containing air and reduces oxygen in the storage atmosphere. FAO's controlled-atmosphere guidance identifies gas containment and maintaining conditions for the required period as essential. Saying that nitrogen is used therefore describes the starting point; how performance is monitored requires separate consideration. (FAO: Controlled atmospheres)

Storage-pest control also depends on more than the name of the gas. FAO explains that results in dried products relate to temperature, relative humidity, exposure duration and insect life stage. This framework shows why validated operating conditions matter; it cannot establish universal settings for every warehouse. (FAO: Pest control)

Nitrogen atmospheres also have a quality-preservation role. A hazelnut study reported favourable lipid-oxidation results under modified atmosphere combined with refrigeration. Product form and temperature also differed in that experiment. Its results cannot be turned into a performance guarantee for a commercial in-shell hazelnut silo. (University of Turin: Original research)

Preserving quality and removing toxins are different outcomes

Nitrogen storage is not a treatment for removing aflatoxins already present. Controlling mould does not establish toxin absence; prevention and removal are different outcomes. (EFSA)

Nitrogen should therefore complement appropriate drying, monitoring and laboratory analysis based on representative sampling. For example, assessing oxidation as a quality indicator does not directly answer a question about aflatoxin concentration. Different controls for the same lot answer different questions.

The published workflow for the in-shell hazelnut storage service we use starts with admission checks for moisture, foreign material and physical defects. Cleaned nuts are weighed, and product movements are tracked through lot identification and barcodes. Classification includes yield assessment and cut checks to evaluate product quality. The nuts are stored under nitrogen in steel silos; barcode records support tracking during dispatch. This explains identification and classification from admission to shipment. Classification checks do not replace chemical aflatoxin analysis. Buyers should separately request analysis based on a sample representing the lot.

Monitor conditions from admission to dispatch

The Hazelnut Research Institute highlights assessing moisture and quality before extended storage, alongside moisture and temperature management during storage. The product's condition at admission should be assessed together with the storage method. (Hazelnut Research Institute)

A sealed system still requires monitoring. FAO's storage guidance discusses moisture movement and condensation in closed systems. This physical mechanism also highlights the importance of maintaining storage conditions for hazelnuts. (FAO: Storage management)

Buyers can organize information requests around admission date, lot identity, monitoring of storage conditions and assessment of any deviations. Codex also emphasizes identifiable lots and matching documentation. An analytical report should therefore remain connected to the product's movement through the supply chain. (Codex)

Representative sampling comes before analysis

Aflatoxins may be distributed unevenly within a lot. The Ministry's laboratory guidance emphasizes combining samples from different positions and grinding and homogenizing the laboratory sample before analysis. A result from a handful of nuts should not be assigned to the whole lot without an explained sampling plan. (Mersin Food Control Laboratory)

A reported “<LOQ” result does not establish absolute absence; it indicates a result below the method's validated limit of quantification. The European Union's sampling and analysis framework defines this limit. Results should be assessed alongside applicable destination-market rules and the intended use of the product. (EU sampling and analysis regulation)

A buyer's documentation request can cover:

• Product form, lot identifier and represented quantity.
• Sampling plan, sampler or organization, and relevant dates.
• B1 and total aflatoxin results, units and quantification limits.
• The laboratory's current accreditation scope for the product and method.
• Storage information and matching of the report to the quotation and shipment.

The value of nitrogen storage belongs within this wider assessment: storage conditions and analytical compliance require different evidence. Define your product form and documentation needs when discussing hazelnut supply, and share your request through our contact page.

Sources

FAO: Controlled atmospheres, FAO: Pest control, University of Turin research, EFSA, Hazelnut Research Institute, FAO: Storage management, Codex, Mersin Food Control Laboratory, EU regulation.