THE EFFECT OF PROCESSING ON THE NUTRITIONAL VALUE OF FINGER MILLET (ELEUSINE CORACANA) SEED
The effect of processing on the proximate composition, anti-nutrient levels and mineral contents of finger millet seed (Eleusine coracana) were analyzed. Diets containing processed finger millet seed (71.4g) per 100g feed were fed to four different groups of weaner rabbit for 56 days. Animals’ fed diet containing unprocessed finger millet seed were used as negative control group and animals’ fed diet containing casein (standard protein) were used as positive control group respectively. Effect of processing methods like soaking, boiling, fermenting and roasting on the finger millet seeds significantly (p<0.05) reduced the anti-nutrient substances like tannins, saponins, phytate and oxalate when compared with their values from the unprocessed finger millet seed. Protein quality parameter’s observed in the animals fed diet containing processed finger millet seeds like True Digestibity (TD), Biological Value (BV) and Net Protein Utilization (NPU) increased in the following order; Roasted finger millet seed (98.41±0.55, 54.85±2.23 and 54.26±2.48), Boiled finger millet seed (95.57±0.93, 52.88±0.96 and 50.13±0.97), Fermented finger millet seed (95.18±0.28, 52.52±1.81 and 49.97±1.67), and Soaked finger millet seed (94.52±0.55, 50.63±0.96 and 47.99±2.46). In conclusion, the results indicated that roasting treatment is the best processing method on finger millet seed for better utilization of its protein content, while fermentation is best in reducing the anti-nutrients contents.
Finger millet (Eleusine coracana), typically a tropical crop, belongs to the group of minor cereals. It is mainly consumed in India and Africa. It is an important cereal because of the excellent storage properties of the grain and the nutritive value, which ishigher than that of rice and equal to that of wheat (Van Wyk and Gericke, 2000). It is also a good source of micronutrients like calcium, iron, phosphorus, zinc and potassium.
Due to the presence of anti-nutrients in grains such as tannins and phytates, these micronutrients are less bioaccessable (Harris and Burns 1978). Among millets, finger millet was reported to contain high amounts of tannins (Ramachandra et al., 1977), ranging from 0.04 to 3.47 per cent (cataechin equivalent).
Poor iron availability (represented by low ionizable iron) in finger millets are due to their high tannin content which adversely affect the nutritional quality of the grains (Udayasekhara Rao and Deosthale, 1988). Tannins reduced apparently digestibility of protein and energy (Jansman et al., 1993). Cyanide readily and reversibly binds to a number of enzymes and proteins containing iron including haemoglobin, myoglobin, catalase and the cytochrome system (Ahmed et al., 1996; Uvere, et al., 2000). Phytate interference with mineral absorption, especially calcium and zinc has been reported (Doherty et al., 1982). Oxalates affect calcium and magnesium metabolism (Oke, 1969), and react with protein to form complexes which have an inhibitory effect on peptic digestion (Oboh, 1986). Saponins act on the cardiovascular and nervous system as well as the digestive system (Gestener, et al., 1966). Another anti-nutritional factor that affect the availability of some nutrients is phytate, a naturally occurring phosphorus compound which significantly influences the functional and nutritional properties of foods. It is the main phosphorus store in mature seeds. Phytate has a strong binding capacity, readily forming complexes with multivalent cations and proteins.