ORIGINAL ARTICLE Hydration kinetics of Carioca beans at different pHs Samouel Olugbenga Oladele 1,3 | Oluwatooyin F. Osundahunsi 2 | Leo A. S. Agbetoye 1 | Pedro E. D. Augusto 3 1 Department of Agricultural and Environmental Engineering, Federal University of Technology, Akure, Ondo State, Nigeria 2 Department of Food Science and Technology, Federal University of Technology, Akure, Ondo State, Nigeria 3 Department of Agri-food Industry, Food and Nutrition, Luiz de Queiroz College of Agriculture (ESALQ), University of São Paulo (USP), Piracicaba, São Paulo, Brazil Correspondence Pedro E. D. Augusto, Avenida Pádua Dias, 11— Piracicaba, SP 13418-900, Brazil. Email: pedro.ed.augusto@usp.br Funding information National Council for Scientific and Technological Development (CNPq, Brazil), Grant/Award Number: 401004/2014-7; São Paulo Research Foundation (FAPESP, Brazil) , Grant/Award Number: 2016/18052-5; Tertiary Education Trust Fund (TETFUND, Nigeria), Grant/Award Number: FUTA/VCPU/ TETFund/155/2014AST&D; TETfund; National Council for Scientific and Technological Development; São Paulo Research Foundation Abstract This work investigated the effect of pH of the soaking solutions on the water uptake of Carioca bean (Phaseolus vulgaris) at 25  C. Four soaking solutions at pH levels of 3.1, 6.0 (natural value), 9.1, and 12.1 were prepared using dilute HCl or NaOH. The moisture content over the soaking time exhibited sigmoidal shapes, which were adequately modeled. The solutions with pH 3.1 and 9.1 converged to ~6.0 during the process, which were attributed to the solids leakage and ions diffusion through the grains. The equilibrium moisture and the hydration rate increased by changing the pH from 6.0 to 12.1, while the lag phase showed the opposite behavior. The pH of the soaking solutions affected the mass transfer behavior in both seed coat and cotyledon, dem- onstrating changes on both proteins and polysaccharides. This work demonstrated a simple approach for enhancing the hydration process of grains. Practical applications In the industries where grains are utilized, hydration process is an important process prior to several other steps like germination, cooking, components extraction, and fermentation. The process requires improvement because of slowness, discontinuity, and energy consumption. Our results showed that the water uptake characteristics of Carioca beans were greatly influ- enced by the pH of hydration solution, which could be a simple approach for enhancing the pro- cess. This work contributes to the explanation of the grain hydration behavior and possibly enhancing focusing on its optimization. 1 | INTRODUCTION Pulses are members of Fabaceae or Leguminosae family, and world’s third largest plant group in production. They have been an essential part of human diet for centuries as they play crucial roles in healthy diets, sustainable food production, and food security. Pulses are con- sumed across the globe in various forms, directly or in stews, flours, purées, accompaniments, snacks, and desserts. Their consumption offers humans health and nutritional benefits. They are also used for animal feed and other food processing (such as extractions of oils, proteins, etc.). The seed structure and grain composition are rich in the supply of protein, essential amino acids—a complement to cereals, carbohydrates, micronutrients, and high quality dietary fiber (Foyer et al., 2016; Javaloyes, 2016). Prior to the consumption, utilization and further processing in wide varieties, the dried grains need to be rehydrated. Hydration is a complex food moisture restoring process, where food is restored to its first characteristics. The need for deep insight into hydration pro- cess become so important considering abundant variety of dehydrated products, demand for processing, concerns for attaining quality, nutri- tion and health requirements, and conserving energy. The degree of grains’ imbibition is influenced by the seed coat composition, preced- ing drying process, permeability of seed coat and hilum, and water availability. The process is characterized with time-consumption, energy utilization, and discontinuity (Kaptso et al., 2008; Miano & Augusto, 2015; Stanley & Aguilera, 1985). Several approaches have been explored to enhance the hydration process using high temperature, high hydrostatic pressure (Ibarz, Gon- zález, & Barbosa-Cánovas, 2004), cyclical pressure changes (Naviglio, Formato, Pucillo, & Gallo, 2013), and ultrasound (Ibarz et al., 2004; Miano, Pereira, et al., 2016; Ulloa et al., 2015). However, although higher temperatures enhance the hydration rate, yet this approach Received: 6 December 2017 Revised: 18 April 2018 Accepted: 28 April 2018 DOI: 10.1111/jfpe.12908 J Food Process Eng. 2018;e12908. wileyonlinelibrary.com/journal/jfpe © 2018 Wiley Periodicals, Inc. 1 of 7 https://doi.org/10.1111/jfpe.12908