Microgreens were sealed in a standard zip bag, placed in the fridge, and labelled with a 10-day shelf life. On day five, a customer reports yellowing and an off smell. The problem is not the fridge and not the label — CO₂ and ethylene from cellular respiration accumulated inside the bag, moisture condensed as droplets on the product and triggered bacterial growth. Proper packaging is not a storage container — it is an active component that manages the atmosphere inside.
Quick Glossary
- Cold Chain — a continuous system for maintaining low temperatures from harvest to the consumer; any break irreversibly accelerates product degradation
- MAP (Modified Atmosphere Packaging) — packaging with a controlled gas composition (reduced O₂, elevated CO₂) that slows cellular respiration and microbial growth
- Perforated film — film with micro-perforations that allows gas exchange and maintains humidity without condensate accumulation; suitable for actively respiring products
Why Standard Packaging Is Not Enough
A living leaf continues to respire after cutting: it consumes oxygen and releases CO₂ and water vapour. In a sealed package without gas exchange, oxygen is rapidly depleted, CO₂ accumulates, and the product shifts to anaerobic respiration — it begins to ferment and an off odour develops.
Water vapour released during respiration condenses on the cold package walls and returns as droplets onto the product. Droplets on leaves at even +4°C create an environment for bacterial growth and accelerated senescence.
A hermetically sealed package without MAP can temporarily maintain appearance — but internal degradation processes continue without visible symptoms until the problem becomes obvious.
Perforated Film vs MAP: When to Use Each
Perforated film is a simple and inexpensive option for short shelf lives and direct sales. Micro-perforations allow gas exchange and prevent condensate accumulation. The downside: it does not actively control the atmosphere — it simply prevents conditions from becoming critical. For product with a 3–5 day shelf life and direct delivery to the consumer, this is sufficient.
MAP — active atmosphere management: the package is sealed after introducing a gas mixture (typically 3–5% O₂, 10–15% CO₂, balance N₂). Reduced oxygen slows cellular respiration and aerobic bacterial growth. Elevated CO₂ suppresses most pathogens and slows senescence. Nitrogen is an inert filler that displaces air.
MAP genuinely extends shelf life — but only with an unbroken cold chain. MAP at +2°C and a hermetically sealed bag at +8°C will yield roughly the same result. MAP is a tool that amplifies the effect of the cold chain, not a substitute for it.
Gas composition must be calibrated for each specific crop: different plants have different sensitivity to CO₂ and O₂. Too high CO₂ for some crops causes "gas burn" — brown spots on leaves. MAP must be developed through testing, not from generic tables.
Temperature: Where Losses Occur and How Much
Storage at +2–4°C is the standard for microgreens. At +6°C the degradation rate doubles; at +10°C it is four times higher than at +2°C. A retail refrigerator typically holds +4–8°C — this is a built-in shelf life loss that must be factored into labelling.
The critical moment is not stationary storage but the transition stages: harvest, sorting, packing at room temperature, loading into the vehicle, unloading at the store. Every transition above +4°C is a thermal load on the product.
Solutions: a packaging area cooled to +10–14°C, or a maximally shortened packing process. Insulated boxes with ice packs for transport. Pre-cooling the product immediately after cutting before packing, where technically feasible.
Container or Bag: Not Just an Aesthetic Question
A rigid container protects the product from mechanical damage during transport — and every cell damage triggers an ethylene burst and accelerates senescence. A soft bag is more economical but when stacked, the product at the bottom is compressed.
A rigid container with a sealable film lid suitable for MAP is the standard for retail supply. A soft perforated bag is suitable for farmers' markets and direct sales.
Important: packaging must be food-grade with appropriate material markings. For HACCP — retain the packaging material specification as a document confirming food contact suitability.
Three Mistakes That Cost the Most
Packing warm product. Cut microgreens that have not been pre-cooled and are packed at room temperature are already beginning to degrade inside the package before the fridge is reached. Product temperature at packing matters more than the fridge temperature itself.
Setting shelf life without accounting for the real distribution chain. If the shelf life test was conducted in your own fridge at +2°C — that is not the real chain. Test under conditions that reproduce the full journey: +2°C after packing, +8°C as in a retail fridge, and evaluate at the end of the declared shelf life.
Ignoring crop differences when selecting packaging. Basil is sensitive to both cold and CO₂ — a MAP that works for radish may cause burn in basil. For each crop, run a separate test when introducing MAP.
Signs That Packaging and Storage Are Set Up Correctly
- Product at the end of its declared shelf life under real retail storage conditions is green, turgid, and odour-free
- No condensate inside the packaging
- Product temperature at retail acceptance does not exceed +4°C
- Packaging material specification is on file in the documentation