Journal of Cereal Science 36 (2002) 125±133 doi:10.1006/jcrs.2002.0463, available online at http://www.idealibrary.com on 1 Protein Nutritional Quality of Infant Cereals during Processing D.PeÂrez-Conesa*, G. Ros and M. J. Periago Department of Food Science and Human Nutrition, Faculty of Veterinary, University of Murcia, Spain Received 1 May 2001 ABSTRACT The most common food for weaning at the age of 4±6 months is cereal since is that it is a good source of high quality protein. However, processing may affect this quality. The aim of the present study was ascertain the changes that take place during four processing stages of infant cereals (in the raw materials, after roasting, after enzymatic treatment and drum drying, and in the commercial product), the following protein nutritional parameters: crude and true protein (CP and TP, respectively), in vitro protein digestibility (IVPD), free amino acids (FAA), calculated protein ef®ciency ratio (C-PER) and total amino acids pro®le. Of the infant cereals studied two contained gluten (`Multicereal' and `Wheat') and two were gluten-free (`Growth' and `Rice and carrot'). All the parameters studied were affected by the different processing stages, but none showed a clear trend. The CP and TP content decreased after heat treatment (roasting) with a consequent increase in FAA content due to protein hydrolysis and the release of amino acids. IVPD remained stable during the processing stages in all the infant cereals, except in `Wheat', while C-PER increased signi®cantly. Infant cereals containing gluten showed higher CP and TP contents, and also higher IVPD than gluten free cereals, in which a digestibility value higher than 75% was reached. The overall content of essential amino acids, including sulphur amino acids, was acceptable (equal to or higher than FAO/WHO recommendations), although lysine (Lys) was the limiting amino acid in all the infant cereals. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: infant cereals, protein quality, protein digestibility, essential and non-essential amino acids. INTRODUCTION Good nutrition is essential during the critical period of infancy to promote optimal growth and develop- ment 1 . At 4 months, the body's homeostatic mechanisms are mature and capable of using a wide range of foods with a higher concentration of nutrients than in mature human milk 2 . Weaning usually starts with granulated foods of small particles that do not need be chewed, or have a thicker texture (bigger particles) to stimulate infant mastication before swallowing 3,4 . Cereals, incorporated as ¯ours, are the commonest food recommended by paedia- tricians to start weaning at this age because of their high energetic load, based on their carbohydrate and protein contents (77±78% and 12±13%, respec- tively). However, the nutritional quality of these nutrients is low in the raw materials, and they have to be processed to improve nutritional quality and to make them more acceptable to infants. The main goal of technological treatment, which includes roasting and enzymatic treatment, is to improve the organoleptic characteristics and to increase ¯our solubility. However, processing will also cause 0733±5210/02/050125  09 $35.00/0 # 2002 Elsevier Science Ltd. All rights reserved. ABBREVIATIONS USED: CP  crude protein; TP  true protein; IVPD  in vitro protein digestibility; FAA  free amino acids; DW  dry weight; g  gram; mg  milli- gram; N  nitrogen;  C  degree celsius; P  probability; S statistical difference.  Corresponding author. D. Pe Ârez-Conesa, Unidad Docente de Bromatologõ Âa e Inspeccio Ân de Alimentos, Facultad de Veterinaria. Universidad de Murcia. Campus de Espinardo, Espinardo 30071- Murcia (Spain). Tel: +34 968364794/34 968364798; Fax: 34 968364798; E-mail: dario@um.es