QUANTIFYING THE EFFECTS OF POSTHARVEST STORAGE AND SOAKING PRETREATMENTS ON THE COOKING QUALITY OF COMMON BEANS (PHASEOLUS VULGARIS) PETER K. KINYANJUI 1 , DANIEL M. NJOROGE 2 , ANSELIMO O. MAKOKHA 1 , STEFANIE CHRISTIAENS 2 , DANIEL N. SILA 1 and MARC HENDRICKX 2,3 1 Department of Food Science and Technology, Faculty of Agriculture, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya 2 Laboratory of Food Technology, Leuven Food Science Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M 2 S), KU Leuven, Kasteelpark Arenberg 22 Box 2457, 3001 Heverlee, Belgium 3 Corresponding author. TEL: 132 16 321572; FAX: 132 16 321960; EMAIL: Marc.Hendrickx@biw.kuleuven.be Received for Publication June 1, 2015 Accepted for Publication March 15, 2016 doi:10.1111/jfpp.13036 ABSTRACT Cooking quality of common beans greatly influences acceptability. The objective of this study was to quantify the effect of bean type, storage time, temperature and relative humidity (RH) on the cooking time of four bean types grown in Kenya. Beans were stored under different temperature (25, 35 and 45C) and RH (75 and 83%). After sampling, they were pre-soaked or not and cooked to gener- ate cooking curves which were subjected to nonlinear regression. Significance of the different variables was evaluated using mixed model regression. Higher stor- age temperatures (35 and 45C), higher RH (83%) and extended time significantly increased lag phase and cooking time. Soaking pretreatments reduced cooking time. Canadian wonder and Pinto beans took long thus hard-to-cook while Rose coco and Red haricot took short cooking time, thus, easy-to-cook. This work demonstrated the critical nature of bean type, storage and pretreatment condi- tions in influencing bean cooking quality. PRACTICAL APPLICATIONS The hard-to-cook (HTC) problem in common beans is one of the main problems leading to low consumption of beans. This manuscript provides information on the easy to cook and HTC bean varieties grown in Kenya. The roles of storage temperature and relative humidity on predisposing beans to the HTC problem is discussed including the optimal storage conditions. Finally, the effect of pre- treatment conditions and cooking on overall cooking time is highlighted. Soaking in distilled water and Na 2 CO 3 significantly reduced the cooking time of the beans. It is hoped that this information can be translated to practical guidelines for bean breeders, stockists, processors and consumers. INTRODUCTION Common beans (Phaseolus vulgaris), also referred to as dry beans or edible beans, and represents a nutritious food pro- viding essential nutrients such as proteins, iron, calcium, vitamins, carbohydrate and fiber. They constitute an essen- tial part of the diet for over 700 million people in the world (Leterme and Munoz 2002). Their consumption in Eastern and Southern Africa exceeds 50 kg/person/year (Wortman et al. 1998). Common bean genetic breeding programs have produced cultivars with high bean yields, tolerance to pests and diseases, different sizes, colors, shapes and sheen. In addition, beans have different cooking characteristics in terms of cooking time, palatability and broth characteristics (Perina et al. 2014). Previous studies have shown that the per capita consumption of beans in many places has gone down mainly due to the reduced time available to prepare 1 Journal of Food Processing and Preservation 00 (2016) 00–00 VC 2016 Wiley Periodicals, Inc. Journal of Food Processing and Preservation ISSN 1745-4549