LWT 41 (2008) 771–778 Effect of pre-dehulling treatments on some nutritional and physical properties of navy and pinto beans (Phaseolus vulgaris L.) Alex A. Anton à , Kelly A. Ross, Trust Beta, R. Gary Fulcher, Susan D. Arntfield Department of Food Science, University of Manitoba, R3 T 2N2 Winnipeg, MB, Canada Received 14 March 2007; received in revised form 7 May 2007; accepted 10 May 2007 Abstract The effect of pre-dehulling treatments using low and high temperatures on some nutritional and physical properties of navy and pinto beans was investigated. Beans were exposed to water (14%, 28% and soaking 1:5, w/v for 6 h, 16 and 16 h, respectively) to facilitate seed coat detachment prior to freeze drying (FD) for 48 h or heat drying (HT) for 20 or 60 min. Exposure to the highest moisture levels produced the largest seed coat yields (17.38–20.91%) and was independent of the drying conditions. The total phenolic content was positively correlated to the 1,1-diphenyl-2-picrylhydrazyl (DPPH) antioxidant activity and increased as the exposure time to HT increased, but it was unaffected by the FD. The nutritional properties of the bean varieties differed significantly, phytic acid was unaffected, and the highest antioxidant activity was observed on the seed coats of HT pinto beans (69.24–84.46% of DPPH discoloration). Significant physical changes were observed for the HT seeds, with the highest yellowness and the lowest peak viscosity detected in the soaked and HT (60 min) beans. r 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. Keywords: Dehulling beans; Pinto beans; Navy beans; Phytic acid; Antioxidant activity; Flour viscosity 1. Introduction Common bean (Phaseolus vulgaris L.) is a traditional food in the human diet, as it is low in fat and rich in proteins, vitamins, complex carbohydrates, and minerals. In addition to contributing nutritional requirements, consumption of dry beans has been linked to reduced risk of heart disease (Anderson et al., 1984), obesity (Geil & Anderson, 1994) and cancer (Azevedo et al., 2003; Garcia- Gasca, Salazar-Olivo, Meniola-Olaya, & Blanco-Labra, 2002). Economically, beans are an important crop in North America, since their production and export has increased significantly in recent years. In Canada, navy and pinto beans are among the most produced and consumed pulses (Agriculture and Agri-Food Canada, 2006). However, widespread use of beans as a primary staple food has been limited by the presence of antinutritional factors, which might produce adverse effects for human and animal nutrition. Some of these compounds include enzyme inhibitors, lectins, phytates, cyanoglycosides, and phenolics (Martin-Cabrejas et al., 2004). Some publications on P. vulgaris have focused on antinutritional aspects of seed coat polyphenols (Barampama & Simard, 1993; Elı´ as, Ferna´ndez, & Bressani, 1979). However, polyphenols have contradicting positive effects on human health and it has been reported that they have anticarcinogenic and anti- oxidant properties (Gamez et al., 1998). It is generally believed that antioxidants scavenge free radicals and reactive oxygen species and can be extremely important in inhibiting oxidative mechanisms that lead to degenera- tive diseases (Madhujith & Shahidi, 2005). Recently, antioxidant activity was reported in extracts, condensed tannins, and pure flavonoids from colored genotypes of common bean seed coats (Beninger & Hosfield, 2003; Madhujith & Shahidi, 2005; Gutierrez-Uribe, Serna- Saldivar, Moreno-Cuevas, Hernandez-Brenes, & Uajardo- Touche, 2005). Because of their nutritional and health-promoting properties, the development of value-added bean-based products for new market opportunities in the functional ARTICLE IN PRESS www.elsevier.com/locate/lwt 0023-6438/$34.00 r 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.lwt.2007.05.014 à Corresponding author. Tel.: +1 204 474 9866; fax: +1 204 474 7630. E-mail address: umanton@cc.umanitoba.ca (A.A. Anton).