CONICET | Buscador de Institutos y Recursos Humanos

Salvia hispanica L., whose common name is chia, is native to southern Mexico and northern Guatemala. Chia seeds have long been used by the Aztec tribes, being important not only for food, but also for medicines and paints. Today, chia is grown commercially in Mexico, Bolivia, Argentina, Ecuador, and Guatemala. Engineering properties of the seed and their dependence on moisture content are necessary in the design of equipment for transporting, storage and/or processing. The knowledge of the morphology and size distribution of chia seeds is essential for the adequate design of the equipment for cleaning, grading and separation. Gravimetric properties are useful for the design of equipment related to aeration, drying, storage and transport. Bulk density determines the capacity of storage and transport systems while true density is useful for separation equipment; porosity of the mass of seeds determines the resistance to airflow during the aeration and drying. The frictional properties, such as the angle of repose and the coefficient of external friction, are important for the design of grains bins and other storage structures whose operation is influenced by the compressibility and flow behaviour of materials. The engineering properties of chia seeds were evaluated as a function of the moisture content, in the range of 4,6 to 17,7% b.s. and their behavior was compared with that of other grains (soybean, cotton, quinoa, amaranth and fenugreek, rapeseed, safflower, sunflower and cumin). The engineering properties showed an important dependence of the seed moisture content. The principal dimensions of seed (length, width and thickness), geometric diameter, specific surface area, volume, equivalent diameter, weigh of a thousand seeds and static coefficient of friction on galvanized sheet and on aluminium increased linearly as increasing the seed moisture content. The average values were: 1.972 mm, 1.287 mm and 0.837 mm, 1.285 mm, 5.20 mm2, 1.21 mm3, 1.32 mm, 0.129 g. 0.28 and 0.30, respectively. An increase in moisture content yields a decrease in bulk and true density, with mean values of 0,692 gcm-3 y 1,069 gcm-3, respectively. The porosity of the bed of grain and sphericity increased or decreased dependent of the range of moisture considered. The means values were 35,25 % y 67,0 %, respectively.