This article appeared in the Fall 2013 issue of Pulse Crop News.

Neil Whatley, Alberta Agriculture and Rural Development

Following a few storage and handling guidelines will ensure pulse crops retain their quality and maximize their marketability. Downgrading of pulse crops can occur when cracked seed coats or split seeds are present in the sample, or if a significant amount of seeds are heated or have a musty odor.

Monitoring stored pulses begins shortly after harvest, with grain spoilage risk increasing if the crop was harvested after an early frost or wet weather. To avoid heating in the bin, green seeds and dockage material should be cleaned out prior to storage.

To achieve optimal grades, long-term storage of pulse crops requires seeds to contain a moisture content of 14 per cent or less and be cooled to 15 degrees Celsius or less. Pulses having a temperature of 10 degrees C will store much longer. Lentil growers need to be aware that some buyers prefer red lentil to have a moisture content of 13 per cent to improve their dehulling and splitting processes.

The following table indicates the number of weeks recommended for safe storage of field pea at various grain moisture contents and storage temperatures. Other pulse crops are similar.

Source: Sokhansanj, 1995

Even if moisture content is low, field pea seeds should be cooled soon after binning if the seed is warm. Pulses with large seeds (field pea and chickpea) continue to breathe or respire after being harvested as moisture equalizes throughout these large seeds. This causes them to go through a sweat period for several weeks after harvest, which raises the temperature and moisture content of the stored grain, producing favourable conditions for mould growth.

Usage of aeration bins is the most effective method to control this situation. When monitoring, one should not rely on readings of average moisture content throughout the bin because there may be hot spots in isolated locations where moisture is high and mould can occur. To avoid spoilage when this respiration occurs, bins should be routinely monitored via probing, and aeration applied as required.

While aeration fans can cool pulses in a matter of days, drying via aeration can take three to four weeks and requires adequate power to provide air flow through the grain. If a grain dryer is required for supplemental heat, air temperatures should not exceed 45 degrees C to prevent seed germination problems with seed destined to be re-planted, or to prevent quality losses due to hardening or cracking of seed destined for food use. Additionally, the sample should not be dried more than four to five percentage points per pass through the drier. For feed pea, dryer temperatures up to 70 degrees C can be applied.

When moving pulse crops, grain augers operated full and at low speeds reduce seed coat cracking and seed splitting. Pulse seeds at 12 per cent moisture content and lower are more susceptible to chipping and peeling when handled.