Texture and interlinked post-process microstructures determine the in vitro starch digestibility of Bambara groundnuts with distinct hard-to-cook levels

Abstract

Particular storage conditions are described to promote the development of the hard-to-cook (HTC) phenomenon for most legumes. However, it is not clearly established whether the HTC phenomenon influences starch digestion kinetics. Therefore, this study explored how the HTC phenomenon influences in vitro starch digestion of Bambara groundnuts, taking into account three distinct HTC levels. Stored Bambara groundnuts required prolonged cooking times. Increasing storage time led to a decrease in the rate constant of texture degradation, signifying the development of the HTC phenomenon. For cooking times of 60 min and 120 min, high HTC level samples exhibited higher rate constants and extents of starch digestion compared to the fresh sample. The higher rate of digestion was attributed to the high hardness that resulted in greater cell rupture and faster access of amylase to starch. Adapting cooking times of Bambara groundnuts with distinct HTC levels to obtain equivalent hardness values and microstructures resulted in comparable starch digestion kinetics. Spectrophotometric analysis overestimated the amount of digested starch, in contrast to the more accurate HPLC analysis, which further provided more insight by quantifying multiple digestion products. This work demonstrates that it is the hardness and interlinked pattern of cell failure (microstructure) that determines starch digestion of Bambara groundnuts with distinct HTC levels.

Bambara Groundnut: An Underutilized Leguminous Crop for Global Food Security and Nutrition

“…The HTC feature is associated with legume cotyledon resistance to softening during cooking, resulting in a prolonged cooking time to attain a desirable texture. Development of the phenomenon can be hereditary (114), and it can also be induced by extended storage under elevated temperature (>25 • C) and humidity (>65%), that is, the ambient storage conditions in humid tropic areas (115). The pectin-cation-phytate model is the most widely accepted postulated mechanism for the development of HTC (114,116): Pectin is present in the middle lamella where it acts as intercellular cement.…”

“…Prolonged cooking of aged seeds also reduced the levels of minerals [Mg, Fe, and Zn; (45)] and protein quality (122). The level of HTC and degree of cooking also influenced starch digestibility of HTC Bambara groundnut (115). Additionally, hardening of beans not only reduces the eating quality but also increases fuel and water consumption during cooking (14).…”

“…This becomes a major problem especially for areas where firewood is used for fuel or water resources are limited. Consequently, the HTC phenomenon is not only inconvenient, it increases the cooking cost and also poses challenges for sustainability, which may limit its potential uptake on a larger scale (115).…”

Effects of Hydrothermal Processing Duration on the Texture, Starch and Protein In Vitro Digestibility of Cowpeas, Chickpeas and Kidney Beans

“…There is an emerging interest in utilising a kinetic approach in describing the starch and protein digestibility of foods [ 18 , 19 , 20 , 21 ]. This is because it allows for the approximation of the nutrient release and/or absorption within the gastrointestinal system as a function of time in response to pH changes and the presence of a wide of range of digestive enzymes.…”

Evaluation of fermented African yam bean flour composition and influence of substitution levels on properties of wheat bread

“…AYB seeds, like most legumes, have been associated with several factors that limit their utilization in food products. These include their hard-to-mill and hard-to-cook attributes as well as long cooking time, which negatively affect their utilization and limit their consumption (Gwala et al, 2019). Aside these afore-mentioned factors, the presence of α-galactosides, soluble fiber (Oboh et al, 2000), and antinutritional factors (ANFs) decreases protein digestibility and nutrient bioavailability (Ene-Obong, 1995).…”