Effects of barley flour and barley protein isolate on chemical, functional, nutritional and biological properties of Pita bread Muhammad H. Alu’datt a, * , Taha Rababah a , Khalil Ereifej a , Inteaz Alli b , Mohammad A. Alrababah c , Ali Almajwal d , Nather Masadeh a , Mohammad N. Alhamad c a Department of Nutrition and Food Technology, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan b Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University, 21,111 Lakeshore Road, Ste Anne de Bellevue, Canada H9X 3V9 c Department of Natural Resources and Environment, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan d Department of Community Health Sciences, King Saud University, P.O. Box 10219, Riyadh 11433, Saudi Arabia article info Article history: Received 3 January 2011 Accepted 25 April 2011 Keywords: Barley proteins isolate Biological properties Nutritional properties Functional properties abstract This study was carried out to investigate the effects of fortification of wheat flour with barley flour (BF) and barley protein isolate (BPI) at three levels; 5, 10 and 15% levels on the chemical composition, nutritional evaluation and biological properties of pita bread. Proteins fractions such as globulin, prolamin, glutelin-1 and glutelin-2 as well as protein isolates were extracted from barley flour and evaluated for protein yield, chemical composition and nutritional quality. Highest yield and essential amino acids contents were obtained in barley protein isolate. SDS-PAGE gels electrophoresis indicated that fortified wheat flour with BPI and BF consists of proteins coming from wheat flour and barley proteins. The contents of essential limiting amino acids in bread were increased from 1.38 to 3.10 g/100 g for lysine and from 0.86 to 1.73 g/100 g for methionine as the ratio of fortification with BF and BPI increased from 0 to 15%. The highest content of total phenolics, antioxidant activity, and inhibitory activity for both angiotensin converting enzyme (ACE) and a-amylase were found in fortified bread with BPI at 15%. Results indicated that bread made from fortification of wheat flour with BF and BPI at 15% showed superior chemical, physico-chemical, nutritional and biological properties. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Protein isolates play an important role in functional properties of food and their products such as water holding capacity, solu- bility, emulsification, gelation and foamability properties (Kinsella, 1976). Technological advancement in the past two decades in the commercial protein production has focused on the use of plant protein sources instead of animal sources (Henry & Kettlewell, 1996). This is very significant contribution as the world pop- ulation is increasing and subsequently the cost of food especially from animal sources is increasing as well. Therefore, the continuous need to improve the nutritional and functional properties of proteins is contributing to the acceleration of plant proteins research (Henry & Kettlewell, 1996). Wheat (Triticum aestivum) is one of the world’s largest edible cereal crops (Sharma, Sekhon, & Nagi, 1999). Wheat products are the least expensive and major source of calorie intake and staple food commodity especially in developing countries including Jordan. Wheat proteins have unique functional and nutritional properties to be used in food applications (Hettiarachchy, Griffin, & Gnanasambandam, 1996). However, wheat flour proteins are defi- cient in some essential amino acids such as lysine lowering the quality and nutritional properties of foods and their products (Dhingra & Jood, 2001). Researchers have tested several blends of food proteins added to wheat flour and food products in order to enhance chemical, functional and nutritional properties of foods and their products (Rakosky, 1989). Ahmedna, Prinyawiwatkul, and Rao (1999) reported that the solubilized wheat protein was incor- porated at 5, 10, 15 and 20% into ice cream, chocolate chip cookies, banana nut muffins and hamburger patties. Barley is a seasonal crop which can grow in a wide range of environmental conditions including arid, semi-arid and wet climates. Barley is well known as an excellent choice for diet fortification in deficient protein areas (Sarac & Henry, 1998). Newman and Newman (2005) have used barley in several food industries such as the brewing industry and even animal feeding. Recently, several studies were recommended to use barley seed in the human diet compared to other seeds due to pharmaceutical and nutraceutical properties * Corresponding author. Tel.: þ962 776579511; fax: þ962 27201078. E-mail address: muhammad.aludatt@mail.mcgill.ca (M.H. Alu’datt). Contents lists available at ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd 0268-005X/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodhyd.2011.04.018 Food Hydrocolloids 26 (2012) 135e143