Protein Quality of Conventional and High Protein Rice and Digestibility of Glutinous and Non-Glutinous Rice by Preschool Children

Abstract

The bulkiness of cooked rice imposes limits on the quantities that can be consumed, especially by infants and small children. Rices of higher protein content should offer a nutritional advantage if protein quality does not suffer. Protein quality of a high protein rice (IR480-5-9, 11.4% protein) was compared isonitrogenously with that of a rice of lower protein content (IR32, 7.1% protein) and with casein by nitrogen balance studies in eight children 12 to 18 months of age. Diets provided 100 to 125 kcal and 240 to 300 mg N/kg body weight/day constant for each child. Non-protein energy was supplied by sucrose and a blend (80:20) of soybean:cottonseed oil. Two 7-day rice dietary periods (alternating IR32 and IR480-5-9) were preceded and followed by 9-day casein control periods. Apparent N absorption from rice (65.7 ± 6.7%) was significantly less than from casein (84.9 ± 4.2%). Apparent N retention from IR480-5-9 was 23.0 ± 2.5%, that from IR32 28.6 ± 9.4% (initial casein period: 35.2 ± 5.9%). Digestibility of these two non-glutinous rices was compared with that of a glutinous variety, IR29, in further studies in which equal quantities of rice (13.2 or 16.5 g/kg body weight/day) were consumed. Fecal wet weight tended to be lower during rice consumption than during consumption of the control diet, significantly so only for IR29. Fecal dry weight, fecal energy and calculated fecal carbohydrate did not differ between rice and control periods. There were significant linear correlations of fecal wet and dry weight with fecal energy for both the rice and control diets. Although several factors suggested that the protein quality of IR480-5-9 was inferior to that of IR32, this would more than be offset by the increased protein content of the former when equal quantities of rice were consumed. Overall digestibility of rice by children appeared to be excellent and should not limit consumption by this age group.