Study of the effect of using different levels of tahinah (sesame butter) on the protein digestibility-corrected amino acid score (PDCAAS) of chickpea dip † Moez Al-Islam E Faris and Hamed R Takruri* Department of Nutrition and Food Technology, Faculty of Agriculture, University of Jordan, Amman, Jordan Abstract: This study was conducted to investigate the effect of using different proportions of tahinah (0–25%) on the protein digestibility-corrected amino acid score (PDCAAS) of chickpea dip and to evaluate this parameter when chickpea dip is consumed with wheat bread. Protein quality was evaluated using the methods of amino acid score and true protein digestibility in weanling Sprague– Dawley rats. The levels of tahinah that provided the best true protein digestibility and protein digestibility-corrected amino acid score were 20 and 25%. Values of true protein digestibility were significantly higher (P 4 0.05) than for the other types of chickpea dip (0.87 and 0.88 respectively). The consumption of wheat bread with chickpea dip led to a marked improvement in the true protein digestibility of the protein mixture (0.90); however, the protein digestibility-corrected amino acid score did not change in the same manner owing to the relatively low amino acid score. It can be concluded that the addition of tahinah to chickpea led to an increase in the protein digestibility- corrected amino acid score of chickpea dip (based on laboratory rat requirements for essential amino acids) and that the consumption of chickpea dip with bread led to an improvement in the protein digestibility of chickpea dip but not in the protein digestibility-corrected amino acid score. # 2002 Society of Chemical Industry Keywords: chickpea dip; tahinah (sesame butter); true protein digestibility (TD); protein digestibility-corrected amino acid score (PDCAAS) INTRODUCTION Chickpea (Cicer arietinum L) is a member of the Leguminosae and is the fifth most important legume in the world. 1 It is classified among the high-protein seed crops, with a mean value of 22.2%. 2,3 Chickpea dip, which is prepared from chickpea, tahinah (sesame butter) and lemon juice or citric acid, 4 is a very popular dish in South Asian as well as Mediterranean countries, including Jordan. However, the deficiency of legumes, including chickpea, in sulphur-containing amino acids and the deficiency of sesame protein in lysine are well known. 3,5–8 There are many methods to evaluate the protein quality of food mixtures, including protein digesti- bility, chemical score and protein digestibility- corrected amino acid score (PDCAAS). 9 Digestibility of a protein is defined as the fraction of ingested nitrogen which is absorbed. 10 It can be used as a biological indicator of protein quality and can be measured by rat bioassay as ‘true digestibility (TD)’, in which allowance is made for faecal nitrogen loss on a protein-free diet. 9,11 Chickpea and sesame seeds have been reported to contain different types of antinutritional factors, the most important of which are trypsin inhibitors. 12,13 Such substances have the ability to inhibit the proteolytic activity of the digestive enzymes trypsin and chymotrypsin, thus hindering protein digestibility. The protease inhibitors that have been isolated from soybeans and other legumes are the so-called Kunitz and Bowman–Birk inhibitors. 14 Chemical score is the most theoretically sound and commonly used chemical method. 9,11 However, this method does not take into account the bioavailability of amino acids or protein digestibility. PDCAAS is adopted as a current concept in protein quality evaluation methodology since it is more relevant to human requirements. 15 Therefore, and since varying proportions of tahinah are used in the preparation of chickpea dip, the objective of this work was to study the effect of using different proportions of tahinah in improving the protein digestibility and PDCAAS of chickpea dip. Because chickpea dip is usually consumed in East (Received 19 February 2001; revised version received 19 June 2002; accepted 20 September 2002) * Correspondence to: Hamed R Takruri, Department of Nutrition and Food Technology, Faculty of Agriculture, University of Jordan, Amman, Jordan E-mail: htakruri@agr.ju.edu.jo † This paper was presented at the First Jordanian Conference for Food and Nutrition, Amman, Jordan, 11–12 July 2001 # 2002 Society of Chemical Industry. J Sci Food Agric 0022–5142/2002/$30.00 7 Journal of the Science of Food and Agriculture J Sci Food Agric 83:7–12 (online: 2002) DOI: 10.1002/jsfa.1273