Nutrient retention in microwave cooked germinated legumes Naveeda Khatoon, Jamuna Prakash * Department of Studies in Food Science and Nutrition, University of Mysore, Manasagangotri, Mysore 570 006, India Received 17 January 2005; accepted 16 March 2005 Abstract The effects of germination on the cooking quality and nutrient retention in pressure and microwave-cooked Bengal gram, green gram and horse gram were studied. Ungerminated (UGL) and germinated legumes (GL) cooked in a microwave oven, and under pressure were analysed for moisture, protein, ash, iron, thiamin, ascorbic acid, in vitro protein digestibility (IVPD) and starch digestibility (IVSD) and bioavailable iron. Results revealed that microwave cooking required more water and time than did pressure cooking. The range of analysed constituents on dry weight basis in UGL and GL legumes, respectively, were as follows: protein, 18.2–23.5 and 19.4–25.7 g, ash, 2.1–2.9 and 2.2–2.9 g, iron, 5.4–7.3 and 7.3–10.3 mg, thiamin, 0.10–0.34 and 0.54–1.83 mg, ascorbic acid, 2.4–3.9 and 3.1–25.6 mg/100 g. The effect of germination and method of cooking on nutrient retention varied, depending on nutrient and severity of heat treatment. Microwave cooking caused 36–57% reduction of ascorbic acid while pressure cooking caused 10–30% loss. The IVSD in raw samples ranged from 18.4% to 22.1% in UGL and 33.6% to 43.6% in GL. Cooking of UGL and GL, by both methods, increased the starch digestibility threefold. The IVPD of raw UGL ranged from 64.6% to 66.2% and that of GL was 72.4–73.9%. In cooked UGL the IVPD ranged from 70.9% to 82.3% and, in GL, from 78.4% to 84.2%, showing a significant difference in cooking methods only in UGL. The iron bioavailability ranged from 11.5% to 18.7% in raw UGL while it was 18.3–20.6% in GL. GL had a higher content of thiamin and ascorbic acid, higher protein and starch digestibility and bioavailable iron, even after cooking. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Ungerminated legumes; Germinated legumes; Pressure cooking; Thiamin; Ascorbic acid; Protein and starch digestibility; Bioavailable iron 1. Introduction Legumes, consumed after processing and germina- tion, are most economical food (Jaya & Ventkataraman, 1980). This process is also an appropriate low cost low technology option for household processing in lesser developed countries (Wang, Lewis, Brennan, & Westby, 1997). It causes important changes in the biochemical, nutritional and sensory characteristics in legumes. It is known to enhance the nutritional value of legumes, by increasing essential amino acids, protein digestibility, amino acid availability and certain vitamins, including thiamin, riboflavin, niacin and ascorbic acid (Fernandez & Berry, 1988). A decrease in CHO content of legumes, ranging from 35% to 40% on germination, has also been reported by many workers (Chavan, Kadam, & Salun- khe, 1987; Fernandez & Berry, 1988; Giami, 1993; Jaya & Ventkataraman, 1980; Subbulakshmi, Kumar, & Venkataraman, 1976). The decrease in total CHO and reducing sugar contents was attributed to their con- sumption, as a source of energy, during the germination process (Khalil & Mansour, 1995). An increase in the digestibility of starch/CHO, due to metabolic and struc- tural changes, hydrolytic breakdown and increased amy- lolytic activity has been reported (Adsule, Kadam, & Salunkhe, 1987; Chavan et al., 1987). Germinated legumes can be consumed as such or processed further 0308-8146/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2005.03.007 * Corresponding author. Tel.: +91 821 2515525x67. E-mail address: jampr55@hotmail.com (J. Prakash). www.elsevier.com/locate/foodchem Food Chemistry 97 (2006) 115–121 Food Chemistry