Mustard is considered to be dry at 9.5 per cent seed moisture. For safe, long-term storage the seed should be at nine per cent moisture. If the moisture of the grain is between 9.5 and 15 per cent, drying is recommended to ensure safe, long-term seed storage. When moisture is greater than 15 per cent, the drying should occur in two stages. The grain should be first dried down to 13 per cent moisture and allowed to cool to the outside temperatures. The grain can then be dried down to nine per cent and allowed to cool before being placed in the bin. Drying should not exceed 65˚C (150˚F) air temperature or 45˚C seed temperature. It is important to remember that mustard seed is denser than cereal seed and that it will require two to three times more static pressure to force the air through the crop.

Aeration is used to change the temperature of the grain in storage and reduce moisture levels. Aeration should begin when the grain first enters the bin and continue until the grain is near the temperature of the outside air. When the outside temperature has cooled by 5 to 10˚C, the mustard should be cooled again. Mustard should be stored below 18˚C and, for safe storage, should be kept as cool as possible.

When first placed in the bin, the seed will still have a relatively high respiration rate for up to six weeks. Heat and moisture, byproducts of respiration, will increase the risk of spoilage. Hot spots can spread rapidly throughout the bin making frequent monitoring very important – especially in those first six weeks. The grain at the bottom of the bin will dry first and will have a slightly lower moisture content. For safe storage, it is important to not only monitor stored mustard frequently but also to check different areas of the bin for temperature and moisture conditions. If possible, turn at least 1/3 of the bulk in the bin to minimize risk of spoilage from initiating.

The amount of dockage will also influence the risk of spoilage. Dockage can raise the moisture content of the grain to result in heating & moulding; if possible, it should be removed prior to long term storage. Additional tips and research about monitoring grain temperature and preventing spoilage can be found on the Canadian Grain Commission’s website.

Storage insects

As an oilseed, mustard does not have frequent problems with insect pests in storage. Most commonly, insects observed in stored mustard are related to poor storage conditions and fungal growth associated with moist conditions.

Pscocids (a.k.a. book lice) are an example of fungus-feeding insects. Although not damaging to the commodity itself, they are an indication of fungal growth. Cooling and bringing down the moisture level in the storage bin will stop the fungal growth and in turn eliminate the fungal-feeding insects.

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