Lentil and Fava Bean With Contrasting Germination Kinetics: A Focus on Digestion of Proteins and Bioactivity of Resistant Peptides

Abstract

Germination offers advantages to improve legume protein digestibility as it disintegrates seed structure and hydrolyzes proteins and anti-nutrients. Seed permeability (related to polyphenol content of seed coats) is an important factor affecting the duration of seed germination and its impact on protein digestibility and bioactivity. The objective was to compare the effect of seed germination on protease activity, structure, and proteolysis of four selected legumes with contrasting seed coat polyphenol profiles (gray zero-tannin lentil [GZL], beluga lentil [BL], and dehulled red lentil [DL]; and zero tannin/low vicine–convicine fava bean [ZF]). Protein hydrolysis was characterized during germination and digestion with respect to proteins, peptides, and free amino acids (FAAs). In vitro antihypertensive and antioxidant activities of digests were investigated, and the peptidomic characterization [high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS)] and identification of bioactive fragments in intestinal digests were performed. Regardless of the seed type, germination increased protease activity and reduced the levels of phytic acid, trypsin inhibitors, and tannins (only in BL). A significant proteolysis of the 7S and 11S globulins and a concomitant increase of peptides and FAAs were observed in all sprouted legumes. Digestion kinetics in sprouts revealed a faster generation of FAAs and peptides than in dry seeds, with changes being more evident for DL, associated with a faster imbibition, germination, and sprout growth. In contrast, BL sprouts showed the lowest protein digestibility, likely due to a lower protease activity, seed structure disintegration, and higher anti-nutrient levels in comparison to GZL, DL, and ZF. Moreover, the digestion of sprouts resulted in a higher number of resistant peptides in DL and ZF that matched with previously reported bioactive sequences, suggesting a promising health potential of legume sprouts that was confirmed in vitro. The results suggested that the germination process improved protein digestibility and the health-promoting potential of lentil and fava bean proteins although these changes were more evident in DL due to its rapid imbibition, faster germination, and sprout development. This study will provide important information for either plant breeders to develop legume varieties with permeable seed coats or food producers that could use dehulled seeds for efficient production of sprouts as sustainable food sources of plant proteins with improved nutritional and healthy properties.

Development of Antioxidant and Nutritious Lentil (Lens culinaris) Flour Using Controlled Optimized Germination as a Bioprocess

“…Germination time caused a more pronounced impact than temperature on the content of this antinutritional compound, which decreased as germination time increased, especially at higher temperatures ( Figure 4 ). In agreement with our results, previous studies have shown reduced phytic acid content in sprouted cereals and legumes [ 18 , 36 , 42 , 52 ]. The results of the present study suggest that activation of endogenous phytases, enzymes that hydrolyze phytic acid to lower inositol phosphates and free phosphorus in sprouted lentils occurs at longer sprouting times, and reductions of 50% in the levels of this compound can be achieved at germination times of 5 days ( Figure 4 ).…”

“…The maximum protein value in sprouted lentil flour was predicted at 22 °C and 3 days ( Table 2 ). These results agree with studies performed by other authors where an enhancement in protein levels was observed during lentil germination beyond 3 days at 20–25 °C [ 36 , 37 , 38 ]. The high amino acid biosynthetic activity that takes place during germination and the synthesis of enzymes in sprouting seeds [ 38 , 39 ] may be responsible for the increased protein levels in sprouted lentil flour.…”

“…GABA is synthesized by the decarboxylation of L-glutamic acid catalyzed by (GAD). Sprouted lentils are potential dietary sources of GABA due to their high protein and L-glutamic acid concentration [ 36 ]. Germination causes the partial hydrolysis of proteins, increasing the availability of free glutamic acid, which together with the activation of GAD [ 61 ] are responsible for GABA enhancement in sprouts obtained at higher temperatures and longer germination times.…”

Adzuki bean (Vigna angularis): Chemical compositions, physicochemical properties, health benefits, and food applications

“…It is expected that more methods to accelerate germination can be developed. It was reported that the contents of certain antinutritional factors (e.g., trypsin inhibitor) of certain legumes decreased with the prolongation of the germination process (Bautista‐Expósito et al., 2021). This remains to be verified with adzuki beans.…”

Isolation of bioactive peptides and multiple nutraceuticals of antidiabetic and antioxidant functionalities through sprouting: Recent advances

“…Bautista‐Expósito et al (2021) germinated different cultivars of fava and lentil beans namely: maxim red lentil from UoS (DL), low tannin/low vicine–convicine fava bean (ZF), low tannin (gray zero‐tannin) lentil (GZL), and beluga lentil (BL) and isolated antioxidative bioactive peptides from them. Their derived flours were subsequently digested with the INFOGEST 2.0 protocol of static in vitro simulated gastrointestinal digestion and sequenced peptides whose antioxidant bioactivities were predicted from the BIOPEP‐UWM™ database include: SKPHTIFLPQFT (from GZT), SRNPIYSNKFGK and NPIYSNKFG (from BL), FLPQFTDADF (from DL), LSPGDVLVIPAGYPVAIK, and YNAAWDPSNGK (from ZF).…”