NUTRITION RESEARCH, Vol. 3, pp. 195-202, 1983 0271-5317/83/020195-08503.00/0 Printed in the USA. Copyright (c) 1983 Pergamon Press Ltd. All rights reserved. PROTEIN QUALITY COMPARISON OF A NEW ISOLATED SOY PROTEIN AND MILK IN CHILEAN PRESCHOOL CHILDREN Juan I. Egaga 1, ~.V.M., M. Sc~, Angel Fuentes 1, M.D., Fred H. Steinke 2, Ph.D. and Ricardo Uauy-, M.D., Ph.. I Institute of Nutrition and_Food Technology (INTA), Clinical Research Center University of Chile and ZCentral Research Ralston Purina Co. ABSTRACT The protein quality of a newly developed soybean protein isolate (SPF-200) and milk were compared using apparent N digestibility (AND), N balance (ANB) and serum biochemical response to graded levels of N intake (NI). Seven healthy well nourished children aged 35 to 62 months, were given for 8 day periods 1.5, 1.25, 1.0 and 0.75 g protein/kg/day of SPF and milk in decreasing order at a constant energy intake of 100 Kcal/kg/day and a vitamin mineral supplement. AND for SPF ranged from 86 to 70% and for milk 83 to 75%, corresponding to highest and lowest NI, ANB for SPF ranged from 63 to 0 mg/kg/day and for milk from 90 to 28 mg/kg/day. Mean individual regressions of daily ANB and NI were ANB = 0.49 NI- 54 for SPF and ANB = 0.51NI -34 milk. The slopes were not signifi- cantly different. Non significant decreases in serum albumin and urea were observed. A significant increase in transaminases was noted at the lowest NI for both proteins. Daily protein allowan- ces to retain 39 mg N/kg/day were 1.27 and 0.91 g protein/kg/day for SPF a~d milk respectively. KEY WORDS: Soy, protein, requirements, children, milk. INTRODUCTION Soy has been one of the most widely used of all vegetable protein sources due to its high biological value together with its technological versatility. Over the last ten years soybean technology has been able to create products with high protein content such as soybean concentrates and isolates. These are used as simulators of animal food and in the manufacturing of hypoallergenic i~ fant formula. Recent interest in isolated soybean protein has increased becau- se its nutritive and technological attributes allow them to be used in wide ra~ ge of alternatives in today's food system. In the present study the protein quality of a newly developed filament li ke isolated soybean protein (SPF-200) Ralston Purina Co., St. Louis, Missouri was evaluated and compared to milk as a reference protein source. The study al so examined the protein and energy requirements of Chilean preschool children used as experimental subjects in the study. PROCEDURES AND METHODS The physical, chemical and nutritional properties of SPF-200 are shown in Table 1. 195