Genetic variability of cooking time in dry beans (Phaseolus vulgaris L.) related to seed coat thickness and the cotyledon cell wall

Authors: BASSETT, AMBER - Michigan State University; HOOPER, SHARON - Michigan State University; Cichy, Karen

Submitted to: Food Research International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2020
Publication Date: 3/1/2021
Citation: Bassett, A., Hooper, S.D., Cichy, K.A. 2021. Genetic variability of cooking time in dry beans (Phaseolus vulgaris L.) related to seed coat thickness and the cotyledon cell wall. Food Research International. 141. Article 109886. https://doi.org/10.1016/j.foodres.2020.109886.
DOI: https://doi.org/10.1016/j.foodres.2020.109886

Interpretive Summary: Dry beans are an affordable, nutritious food found in many cuisines with versatile preparations, but beans frequently require long cooking times when prepared from dry seed. Cooking dry beans can require anywhere from under 20 minutes to several hours depending on factors such as genotype, seed type, seed age, storage and harvest conditions, and whether the seeds have been soaked prior to cooking. The goal of this study was to characterize genetic mechanisms for cooking time variability related to seed physical characteristics, and cell wall and seed coat compositional traits within fast- and slow-cooking genotypes across four seed classes: brown, cranberry, red mottled, and yellow. Soaked cooking time was related to seed weight, cotyledon/seed coat percent, cotyledon cell wall thickness, insoluble cell wall isolate, and total and insoluble fiber. These traits affect cell separation, water uptake, and water transport during cooking. Seed coat layer thickness was related to unsoaked cooking time, but is not important for soaked cooking time.

Technical Abstract: Dry beans are an affordable, nutritious food that often require long cooking times. Storage time and conditions, growing environment, and genotype influence cooking times. Little is known about factors underlying genetic variation for cooking time. Using fast and slow cooking genotypes from four different seed types (brown, cranberry, red mottled, yellow), the objectives of this study were to (1) characterize genetic variability for cooking time across multiple soaking time points; (2) determine the roles of seed coat and cotyledon cell wall physical traits in genetic variability for cooking time; and (3) identify seed coat and cotyledon cell wall compositional differences associated with genetic variability for cooking time. Genotypes were evaluated for cooking time on unsoaked beans and beans soaked for 3, 6, 12, 18, and 24 hr. Cooking times were sharply reduced after 3 hr of soaking and plateaued after 6 hr of soaking. Interestingly, the genotypes in each pair that cooked faster when soaked did not necessarily cook faster when unsoaked. Greater seed coat percentage, cotyledon cell wall thickness, total and insoluble whole seed dietary fiber, and insoluble cotyledon cell wall isolate were genotypic factors associated with longer cooking times of soaked beans. Thicker seed coat macrosclereid- and osteosclereid-layers were genotypic factors associated with longer cooking times of unsoaked beans. These findings suggest that cotyledon cell wall thickness and composition have a significant role in genetic variability for cooking time of soaked beans and seed coat layer thickness relates to the genetic variability for cooking time of unsoaked beans.