Losses of nutrients and anti-nutritional factors during abrasive decortication of two pearl millet cultivars (Pennisetum glaucum)

Losses of nutrients such as starch, lipids, proteins, iron and zinc as well as phytase activity and of recognised anti-nutritional compounds (some insoluble fibres, iron-binding phenolic compounds and phytates) were determined following abrasive decortication of grains from two pearl millet cultivars (Gampela and IKMP-5) with different composition cultivated in Burkina Faso. In both cultivars, abrasion of the starchy endosperm started when about 12% of the dry matter had been removed from grains but lipid and protein losses followed the loss of dry matter. Zinc loss (%) was lower than that of iron; however, both were higher than dry matter losses. By contrast, phytate loss was lower than dry matter loss. Interestingly, decortication led to significant losses in fibres and iron-binding phenolic compounds with different level depending on the cultivar. Changes in phytase activity also differed in the two cultivars (42% and 11% losses of phytase activity in grains from Gampela and IKMP-5 cultivars, respectively, at 12% of abrasion). Hence, decortication of pearl millet grains does not decrease lipid and protein contents but does considerably decrease some anti-nutritional factors (part of the fibres and iron-binding phenolic compounds). However, as mineral contents and particularly iron content decreased while phytate content remains high, decortication may be insufficient to increase Fe and Zn bioavailability.