Kinetic models for water adsorption and cooking time in chickpea soaked and treated by high pressure A. Ibarz a, * , C. Gonz alez b , G.V. Barbosa-C anovas c a Department of Food Technology (UdL-UPV CeRTA), Universitat de Lleida, Escola Te `cnica Superior d’ Enginyeria Agraria, Av. Alcalde Rovira Roure, 191, Lleida 25198, Spain b Department of Chemical Engineering and Metallurgy, Universidad de Barcelona, Mart  ı i Franqu es, 1 08028 Barcelona, Spain c Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA Received 11 April 2003; accepted 13 September 2003 Abstract In this work, the hydration and cooking of common chickpeas (Cicer arietinum) for different hydration degrees were studied. Kinetic models for both cases were developed to describe the evolution of the hydration and the sigmoid-shaped curve of the cooking process. The different cooking times of soaked samples were compared; this included cooking times of unsoaked samples treated with high pressure in the range 275–690 MPa. From the results, it was observed that lower cooking time corresponded to the soaked samples and that the cooking time decreased as soaking time increased. Improvement in the cooking process was not ob- served with high-pressure treatment, in which the observed cooking times were high and corresponded to values analogous to samples soaked for 90 min. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Kinetic model; Water adsorption; Cooking time; Chickpea; High pressure 1. Introduction Legumes play a very important role in the contribu- tion of proteins worldwide, especially among groups of people living under low economic conditions. Depend- ing on the continent or country, the preferences in consumption of the different types of vegetables vary greatly (Aguilera & Stanley, 1985). The vegetables comprise a significant part of the denominated Medi- terranean diet. Traditionally, the vegetables are soaked prior to cooking to hydrate, making them easier to cook. Normally, hydration takes between 12 and 16 h. Among the vegetables, beans (all in its different va- rieties) have been studied the most in the search for possible relations between cooking and hydration times. For dry beans, Rockland and Metzler (1967) studied the effect of the hydration rate on the quality of the product. For different types of dry vegetables, Quast and Da Silva (1977a, 1977b) studied the effects of temperature and hydration in the cooking rate. Burr, Kon, and Morris (1968) studied the effect of water content and the tem- perature and time of storage on the cooking rate of dry beans. Hsieh, Pomeranz, and Swanson (1992) studied the cooking times of azuki and common beans at dif- ferent degrees of ripening, as well as the effect of hy- dration on the times of cooking. Vegetables are not always cooked following harvest; sometimes they are stored for long periods of time which influencing the quality of vegetables. A previous stage of hydration is necessary prior to being cooked (Burr et al., 1968; Hentges, Weaver, & Nielsen, 1991). Aguilera and Stanley (1985) carried out a revision of the kinetics of hydration and cooked vegetables. In the case of cooked beans, it has been postulated that at least two periods exist: (1) an initial period characterized by the breakage of middle lamella and the cellular separa- tion that follows a kinetic type of the first order, and (2) a second period in which the predominant phenomena is the jellification of starch grains of the interior of the cells. High hydrostatic pressure is an emergent technology that provides foods of better quality. The application of high pressure to food destroys the microorgan- isms,modifies the texture, and increases the commercial life of food (Ashie & Simpson, 1996; Cheftel, 1995; Pothakamury, Barbosa-C anovas, Swanson, & Meyer, Journal of Food Engineering 63 (2004) 467–472 www.elsevier.com/locate/jfoodeng * Corresponding author. Tel.: +973-70-2521; fax: +973-23-8264. E-mail address: aibarz@tecal.udl.es (A. Ibarz). 0260-8774/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2003.09.008