Safe storage guidelines for rye and canola
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Canada produces 0.32 million tonnes of rye and 6.9 million tonnes of canola annually. Moisture content and storage temperature are the two major physical factors that influence the deterioration of grain after harvest. The objectives of this work were to determine the rate of deterioration of rye and canola (sometimes referred to as grains) at various moisture and temperature conditions; and to develop safe storage guidelines. Rye and canola with different initial moisture contents (10.0, 12.5, 15.0, and 17.5% (wet basis, wb) for rye and 7.5, 10.0, 12.5 and 15.0% (wb) for canola) were stored at four different temperatures (10, 20, 30 and 40oC) for 16 weeks. Germination, moisture content and appearance of visible mould were measured every week; fatty acid values were measured once every two weeks; and invisible moulds were identified once every four weeks. Moisture content, temperature and storage period had significant effects on germination rate of both the grains (a=0.05). Germination rate of the 17.5% moisture content rye samples and 15.0% moisture content canola samples stored at 40oC reached 0% during the 5th and 4th week, respectively. But it remained above 80% for the lowest moisture samples (10.0% for rye and 7.5% for canola) stored at 10oC even after the 16th week. Moisture content of the samples stored at 10oC increased slightly over time and there were no significant changes in the moisture contents of the samples stored at 20oC. But that of the samples stored at 30oC reached 10.0-13.0% (rye) and 5.0-7.0% (canola); and at 40oC, it decreased to 5.0-6.0% (rye) and 2.0-4.0% (canola) by the 16th week of the study. High moisture samples lost moisture rapidly with increased storage temperature and time. The visible mould stafted appearing during the first week of storage in the high moisture samples (15 and 17.5% for rye; and 12.5 and 15% for canola) stored at 40oC. Appearance of visible mould increased with increasing moisture content and storage temperature. All the samples stored at 40oC showed visible mould irrespective of the moisture content, similarly all the highest moisture samples (17.5% for rye and 15.0% for canola) also showed visible mould regardless of the storage temperature. Aspergillus and Penicillium species occurred predominantly in both the grains throughout the study. Initially, the fatty acid values (FAV) of rye and canola samples were 14.74 +- 1.3 and 22.05 +- 1.5 mg KOH/100 g of dry grain, respectively. The values increased with increasing temperature and time. At the end, the FAV of the 17.5% moisture content rye samples stored at 40oC, had increased to the maximum of 42 mg KOH/100 g of dry grain and that of the 15.0% moisture content canola samples stored at 30oC was 590 mg KOH/100 g of dry grain by the 4th week. Moisture content, storage temperature and time had significant effects on the FAV of both the grains. Rye with <15% moisture content and canola with <10% moisture content can be stored at <-20oC for more than 15 weeks without any considerable quality loss, whereas rye with 17.5% moisture content and canola with 15% moisture content stored at 40oC would have only less than week for post harvest treatments. The available time for the post harvest treatments decreases with increased moisture content and storage temperature.