Yellow bean (Phaseolus vulgaris L.) germplasm with less dietary fiber have shorter cooking times and more bioavailable iron

Abstract

Some yellow-colored market classes of dry bean (Phaseolus vulgaris L.) are valued by consumers as an easy-to-digest, fast cooking alternative to darker colored red and black beans, which in comparison generally have longer cooking times and reduced iron bioavailability. There is evidence that the cooking time of yellow beans is linked to the dietary fiber content and may also contribute to nutrient digestibility and bioavailability. Therefore, 52 fast-, moderate-, and slow-cooking yellow beans with diverse iron bioavailability from five market classes (Amarillo, Canario, Green-yellow, Manteca, and Mayocoba) were selected for total dietary fiber (TDF) analysis. TDF was measured as insoluble (IDF) + soluble (SDF) + oligosaccharides (OLIGO) using method AOAC2011.25. Wide variations in the concentrations of IDF (16.0-23.1%), SDF (1.6-7.7%), OLIGO (1.5-3.4%), and TDF (20.6-31.3%) were detected among the yellow beans with various cooking times. Lower concentrations of IDF in yellow beans were associated with shorter cooking times and higher iron bioavailability. The larger sized Andean yellow beans had more SDF than Middle American. One Mayocoba breeding line from Puerto Rico, PR1146-124, had 42% less OLIGOs than average, and may be useful for breeding low-flatulence beans for consumer acceptability. Fast cooking yellow beans provide the same SDF and OLIGO concentrations as yellow beans with longer cooking times but have the added benefit of shorter cooking times (convenience) and provide more bioavailable iron after cooking.

Keywords: AOAC 2011.25; Dietary fiber; Iron bioavailability; Oligosaccharides; Pulse crops; Yellow beans.

Graphical abstract

Fig. 1

Dot plots illustrating (A) the iron concentrations and (B) the iron bioavailability of 52 yellow bean entries from major yellow market classes, as well as eight non-yellow field control genotypes. Each dot represents the combined means of two field replicates, each measured in duplicate. Iron concentrations are measured as micrograms per gram of soaked, cooked, lyophilized and milled whole beans (dry weight). Iron bioavailability is measured as Caco-2 cell ferritin formation after exposure to an in vitro digestion of soaked, cooked, lyophilized, and milled whole beans. Values are expressed as the percentage of Caco-2 cell ferritin formation (ng ferritin/mg total cell protein) relative to a white kidney bean reference standard that is run with each assay (cv: Snowdon). ∗Significantly (α = 0.05) higher iron bioavailability when compared to the other yellow and non-yellow bean market classes.

Fig. 2

The estimated marginal mean values (emmeans) of dietary fiber (AOAC2011.25) components for each cooking class of the 52 yellow bean accessions. Standard errors for the emmeans are shown as error bars. Mean differences in IDF and Total Dietary Fiber (IDF + SDF + OLIGO) between the cooking classes are shown with alphabets. SDF and OLIGO were not statistically different among the cooking classes (α = 0.05). IDF: insoluble dietary fiber; SDF: soluble dietary fiber; OLIGO: total oligosaccharides (raffinose + stachyose + verbascose).