EFFECT OF FOOD-PROCESSING ON IRON AVAILABILITY OF AFRICAN PEARL-MILLET WEANING FOODS

The effects of different cereal precooking process (roasting and extru sion cooking) on iron availability and protein digestibility of four A frican weaning foods were investigated using in vitro methods. In two weaning foods based on pearl miller, cowpea and peanut, the cereal was extruded (A) or roasted (B), In two other weaning foods having a simi lar composition, a low proportion of milk powder was added and the cer eal extruded (C) or roasted (D). The mean +/- SD iron values (mg/100 g ) were: A, 5.56 +/- 0.18; B, 9.12 +/- 0.93; C, 5.89 +/- 0.23; D, 9.04 +/- 0.85. When the pearl millet was roasted, the iron content was high er than in the extruded weaning foods (P < 0.01). However, the percent of available iron of the roasted weaning foods was very low (B, 1.64 +/- 0.01; D, 0.91 +/- 0.02). The iron availability of the extruded wea ning foods, A and C, was 3.5 times and 6.5 times higher than the corre sponding roasted weaning foods, B and D, respectively. This represente d 332.4 +/- 4.4 and 375.1 +/-: 5.8 mu g of available iron/100 g for A and C, respectively versus 149.5 +/- 0.9 and 82.2 +/- 1.8 mu g of avai lable iron/100 g for B and D, respectively. No significant differences in polyphenol contents were found according to the precooking process of the cereal. The extruded weaning foods showed a higher protein dig estibility of approximately 10% than the roasted ones (P < 0.05). A po sitive correlation was found between in vitro iron availability and pr otein digestibility (r = 0.976, P < 0.02). Despite a high content of i ron, the iron availability of roasted pearl miller weaning foods was q uite low. Extrusion cooking of the cereal improved the protein digesti bility and iron availability of pearl miller weaning foods; however, t he amount of available iron remained insufficient to meet the iron req uirements of infants whatever the cereal processing.