Long-term storage options for peas and lentils
by Trudy Kelly Forsythe
In 2016, Canada exported pulses worth over $1.1 billion to India, accounting for 27.5 per cent of Canada’s global pulse exports for that year. Changes imposed by India in 2017, including a 33 per cent tariff on lentil imports, and mandatory fumigation of pulses destined for India, have producers wondering how they can extend their long-term storage capabilities without impacting quality.
The simple answer is to keep them in the dark, in cool, dry conditions. “For red and green lentils, if they are at 13 per cent moisture content and stored at 15°C, they can be stored for up to a year,” says Dr. Joy Agnew, Project Manager with Prairie Agricultural Machinery Institute (PAMI), Agricultural Research Services. “Peas are considered dry at 16 per cent, but to extend their storage, producers should store them at about 13 to 14 per cent.”
Producers should cool the bin as much as they can in the winter, then monitor it the rest of the year. They do not want to let it get it too cold though, because seed is damaged more easily the colder it gets.
While there is currently no data on exactly how cold is too cold, Agnew says producers report few issues when temperatures are kept between -5°C and -10°C. “Colder than that and we do not know what can happen,” she says, adding producers should try not to handle the pulses if the temperature is below -10°C. “The recommendation is -20°C but I have heard of quite a bit of damage below -10°C.”
Handle With Care
If producers do need to handle pulses below -10°C, they need to do so carefully. This is because all pulses are susceptible to cracking and splitting, especially when cold. If they are really cold and producers do have to handle them, they should use a belt conveyor if available. Another option is a screw conveyor auger, run slowly at a low elevation with a bean ladder.
Agnew admits there are challenges with maintaining an even temperature. “Producers could cool pulses to 5°C or lower, but with natural heating from the sun beating on the sides of the bin, it is difficult to keep cool,” she says. “That is why we say target moisture so they do not have to maintain a specific temperature for a year.”
That said, there is some research-supported data for canola, following a two-year study that looked at the best way to maintain a bin’s lowest temperature, using three strategies: leaving it alone, turning the canola, and aerating the bin with slightly warmer air.
“The bin we left alone had an average temperature of approximately 15°C throughout summer. We were surprised the grain at the centre stayed so cool,” says Agnew. “It is pretty easy to keep the average temperature at 15°C or lower if the grain is cooled over the winter and left alone in the spring, so that is our recommendation for canola, but with pulses we do not know if we can expect the same thing.”
Another tip for extending storage time for pulses is to ensure good ventilation in the head space. Pea producers say they frequently see a crust form at the top of the bins.
“Rapidly warming and cooling from the change in temperatures during the day and night in the head space results in condensation that can create a crust,” says Agnew. “Peas at 16 per cent moisture content — that is a lot of water. You should consider installing active ventilation in the head space to prevent this crusting action.”
The concern with extending storage is that the longer pulses are in storage, the greater the risk for moisture migration and more problems in the bin. This makes monitoring the bin extremely important. “You do not know what is happening in the bin so if you are not watching, you will have no forewarning whatsoever,” says Agnew.
In-bin sensors are the most commonly used by producers these days and PAMI strongly recommends them. But, producers should watch for improved monitoring technology that is currently being developed. “There are newer technologies expected in the next year or two that will create a 3D moisture map of the bin to show the entire moisture content of an entire bin,” says Agnew. “And alternatives to the cables for monitoring temperature in the bin are being developed also.”
Up-to-date information is the best way to avoid spoilage and maximize profit. While there has been some baseline work done over the years to establish drying and wetting characteristics of pulses, it has never been validated or widely adopted.
PAMI researchers are in the second year of a project to validate equilibrium moisture content charts for peas and lentils, to assess the effect of airflow rates on natural air drying, and to determine resistance to airflow in pulses — information that will
help producers minimize the risk of overdrying. The researchers are also collecting baseline data on how repeated wetting and drying cycles affect seed quality.
“We want to give producers confidence they are making appropriate storage management decisions and reducing their risk of loss,” says Agnew.