Focusing on Modern Food Industry (FMFI) Volume 2 Issue 4, November 2013 www.fmfi-journal.org 161 Modeling the Water Absorption Characteristics of Various Local Pearl Millet Grains and Hungry Rice (Digitaria exilis) During Soaking Using Peleg’s Equation Helen O. Agu 1* , Mamudu H. Badau 2 , Usman M. Abubakar 3 1 Department of Food Science and Technology Federal Polytechnic Bauchi P.M.B. 0231 Bauchi, Nigeria 2,3 Department of Food Science and Technology University of Maiduguri. P.M.B. 1069 Maiduguri, Nigeria * 1 agu2001ng@yahoo.com; 2 mamudu_badau@yahoo.com; 3 usmandc@gmail.com Abstract Three local pearl millet grains and two hungry rice cultivars were evaluated for physical properties and chemical composition. Water absorption characteristics of these grains were also determined using Peleg’s equation to fit the experimental data within the linear segment of the curves. Results indicated wide variations in thousand–kernel weight (0.500–9.408 g) and volume (0.0–10.0 g), percent floaters (0.0– 11.433%, in addition to considerable variations in moisture (7.10–8.50%), protein (3.84–7.77%), ash (0.75–1.77%), fat (2.36–3.87%), crude fibre (1.68–2.39) and carbohydrate (76.63–82.98%). The water absorption characteristics of the pearl millet grains and hungry rice studied indicated an initial (0-2 h) higher rate of water absorption of 244.8-406.2, 334.8–540.4, 354.5–620.5, 517.3–872.2 and 566.7–926.7 gH20/100g dry solid for dauro, gero, gayamba, white acha and brown acha respectively followed by slower absorption of 363.8-463.1, 466.5–625.2, 535.5–655.2, 859.9–955.6 and 923.3– 1012.0 gH20/100g dry solid for dauro, gero, gayamba, white acha and brown acha respectively in the later stages. Peleg’s equation gave a reasonable fit to experimental data. The coefficient of determination R 2 varied from 0.9901 to 0.9997. Peleg constant K1 was obtained for the grains studied. The constant K2 decreased (5.4 x 10 -3 - 2.2 x 10 -3 ) with increase in temperature for most of the grains studied. Keywords Modeling; Local Pearl Millet; Hungry Rice; Peleg’s Equation Introduction Pearl millet is an important component in the diet of the poor and a major source of calories and a vital component of food security in the semi arid areas of the developing world (FAO and ICRISAT, 1996). Although hungry rice, (also known as acha, fundi, fairo) (Jideani and Akingbala, 1993) being indigenous to most West African countries (Dendy and Dobraszezyk, 2001) is classified as millet (Rachie, 1974), unlike other millets it is low in protein (Onyenuga, 1968, Miller 1970). However, the protein in acha is unique in that it has greater methionine and cysteine content than other cereal protein (Carbiener et al., 1960). Studies have shown that acha contain high water absorption capacity (Fuanbial, 1998, Lasekan, 1994), a property that could be linked to appreciable amount of pentosans. The grains could be used to produce variety of dishes that require preliminary preparations such as soaking in water, dehulling, fermentation, germination, drying and milling to produce fine flour and grits. The treatment used depends on the product to be produced. Soaking is the most common preliminary process applied to millet grain during the production of various millet based food product (ndaleyi, kunu, masa), as well an important operation in rice parboiling (Engels et al. 1986), thin porridge pap (ogi) (Apena et al. 2006), masa (Ayo et al. 2008), alcoholic beverage (burukutu) (Igyor et al. 2006), and non- alcoholic beverages such as kunun-zaki (Gaffa and Jideani 2001, Ayo and Obeya, 2004, Gaffa et al. 2004) and many others. Peleg (1988) proposed an empirical equation to model water-absorption characteristics of food materials. The equation which is simple compared with other equation based on Fick’s law of diffusion (Crank, 1975) has been applied to various food materials by other researchers (Sopade and Obekpa, 1990, Sopade et al. 1992, 1994, Sopade and Okonmah, 1993, Badau et al. 2005) and was found suitable. Peleg’s Equation Peleg (1988) proposed that: