The effect of seed moisture and temperature on grinding characteristics of quinoa (Chenopodium quinoa Willd.)

Quinoa (Chenopodium quinoa Willd) is a native food plant of the Andean region of South America. Quinoa seeds have remarkable nutritional properties, not only from its high protein content, but also from its good amino acid balance. The aim of the study was evaluate the influence of quinoa seed moisture content (10, 12, 14, 16 and 18%) and temperature (-20, 3, 20 and 40 degrees C, with the initial grain moisture content of 10.5%) on grinding process. Especially the particle size distributions and grinding energy indices were determined. The results showed that the increase of seed moisture content from 10 to 16% caused an increase the specific grinding energy from 6.9 to 8.3 kJ.kg(-1), beside of this as the moisture increased the average particle also increased. The highest changes were observed in the fraction of coarse particles (above 1.0 mm). Interestingly, the mass fraction of fine particles (below 0.2 mm also increased). Other grinding indices also confirmed an increase the grinding energy requirements with the increase seed moisture content. The temperature of seed has little influence on quinoa grinding process. The highest grinding energy requirements were observed when the frozen seeds were ground.