Phytic acid is the principal storage form of phosphorus in legumes, accounting for 50–85% of their total phosphorus content. It is predominantly localized within protein body globoids in the cotyledons. Phytic acid strongly chelates essential minerals such as iron, zinc, calcium, and magnesium, forming insoluble phytate complexes that reduce mineral bioavailability in the gastrointestinal tract (Emkani et al., 2023; Kumar et al., 2021). Additionally, it impairs nutrient digestion by binding directly to digestive enzymes or by sequestering metal cofactors required for enzymatic activity, thereby inhibiting protein and lipid breakdown (Akissoé et al., 2021). As shown in Table 2, cowpeas contain approximately 836 mg/100 g of phytic acid (Abebe and Alemayehu, 2022), which is lower than the 1076.2 mg/100 g reported for soybeans. In non-ruminant animals, the absence of endogenous phytase to hydrolyze phytate further limits the nutritional utilization of legumes such as cowpeas (Simion, 2018).

Hydrolysable tannins consist of a central polyol, typically D-glucose, esterified with phenolic acids, while condensed tannins (proanthocyanidins) are polymers of flavonoids such as catechins, gallocatechins, and epicatechins (Singh et al., 2017; Salim et al., 2023). Tannins reduce nutrient utilization by forming complexes with proteins, carbohydrates, and digestive enzymes, thereby impairing protein and starch digestibility (Khattab and Arntfield, 2009). They are broadly classified into hydrolysable and condensed tannins. In cowpeas, condensed tannins predominate and are known to reduce feed palatability and nutrient absorption by inhibiting key enzymes like trypsin and amylase (Rehman and Shah, 2005). As shown in Table 1, tannin content is higher in cowpeas (390.93 mg/100 g) than in soybeans (225.50 mg/100 g).

Trypsin inhibitors are low-molecular-weight proteins that inactivate digestive enzymes such as trypsin, chymotrypsin, and elastase, thereby impairing proteolysis and reducing AA absorption (Emkani et al., 2023; Salim et al., 2023). The two principal types, Kunitz and Bowman–Birk inhibitors, are well-characterized in legumes (Pedrosa et al., 2021). Their antinutritional effects are primarily linked to growth suppression due to reduced protein digestibility in the gastrointestinal tract (Feng et al., 2007; Khattab and Arntfield, 2009). Trypsin inhibitor activity is higher in soybeans (46.00 TIU/mg) than in cowpeas (21.39 TIU/mg), indicating a greater inhibitory potential in soybeans (Table 2).

The raffinose-family oligosaccharides (RFOs) such as raffinose, stachyose, and verbascose are prominent in cowpeas and are indigestible by monogastrics due to the absence of α-galactosidase (Pedrosa et al., 2021). Their fermentation by gut microbiota leads to excess gas production and flatulence, reducing the acceptance of cowpea-based diets (Ofuya, 2006; Gautheron et al., 2024). As shown in Table 2, the concentrations of raffinose, stachyose, and verbascose in soybeans are approximately 880, 4000, and 170 mg per 100 g, respectively, compared to 119, 388, and 151 mg per 100 g in cowpeas. These values indicate that soybeans contain substantially higher levels of α-galactosides than cowpeas.

Saponins are glycosidic compounds with a triterpene or spirostane aglycone and sugar moieties. They impart a bitter taste, reduce palatability, and can irritate the gastrointestinal tract, thereby decreasing feed intake (Veer et al., 2021; Kumar et al., 2021). Saponins also interfere with nutrient and enzyme activity by forming complexes with digestive enzymes and trace elements such as zinc (Salim et al., 2023). In cowpeas, saponin levels average about 544 mg/100 g (Table 2).

Proteinaceous α-amylase inhibitors in cowpeas block starch digestion by inhibiting mammalian amylases, though they are ineffective against microbial amylases (Salim et al., 2023). This disrupts energy metabolism by reducing starch utilization, potentially impairing animal growth and performance (Shi et al., 2017; Veer et al., 2021). The α-amylase inhibitory activity of cowpeas and soybeans was reported as 1.4–89.5 and 899.30 AIU/kg, respectively. This clearly shows that soybeans have a higher α-amylase inhibitory activity compared to cowpeas (Table 2). Interestingly, the comparatively low α-amylase inhibitor activity in cowpeas may be advantageous for human consumption, as it reduces the risk of excessive inhibition of starch digestion and associated gastrointestinal discomfort.

Lectins (phytohemagglutinins) are carbohydrate-binding glycoproteins that disrupt intestinal integrity by adhering to epithelial cells, thereby facilitating the translocation of pathogens across the gut barrier (Salim et al., 2023). They also impair nutrient utilization by forming complexes with divalent cations such as calcium and iron, which can inhibit enzymatic activity and reduce protein digestibility (Kumar et al., 2021; Veer et al., 2021). As shown in Table 2, hemagglutinin activity ranges from 40 to 640 HU/g in cowpeas and is approximately 692.8 HU/g in soybeans, indicating that both legumes contain appreciable levels of lectins, with soybeans exhibiting slightly higher activity.

Despite their high protein content, cowpeas are deficient in sulfur-containing essential amino acids (EAAs), particularly methionine and cysteine (Menssen et al., 2017; Lubisi et al., 2023). While cowpeas are rich in lysine, leucine, arginine, and tryptophan, the absence of sufficient methionine and cysteine restricts their use in non-ruminant diets. Methionine plays critical roles in protein synthesis, lipid metabolism, and the regulation of antioxidant enzymes (e.g., methionine sulfoxide reductase; Martínez et al., 2017). It is also a precursor for compounds such as cysteine, creatine, and carnitine. Cysteine is central to protein structure, redox regulation via glutathione, and cellular signaling pathways (Muthuraman et al., 2021). Deficiencies in these AAs can impair growth, immune function, and physiological processes in monogastrics.

Overall, the cumulative effect of ANFs and amino acid imbalance in cowpeas limits their direct inclusion in non-ruminant diets. While ANFs disrupt gut integrity, hinder enzyme activity, and reduce nutrient digestibility, resulting in endogenous nutrient losses (Lubisi et al., 2023), a deficiency of sulfur-containing amino acids further impairs growth and physiological performance in non-ruminant animals. Therefore, effective valorization strategies are essential to enhance cowpea protein quality and mitigate antinutritional effects. Techniques such as solid-state fermentation (SSF), sprouting, soaking, roasting, boiling, dehulling, extrusion, drying, and enzymatic treatment have demonstrated efficacy in reducing ANFs and improving amino acid profiles in legume grains (Dueñas et al., 2016; Emkani et al., 2023). These valorization techniques hold promise for improving the nutritional and functional parity of cowpeas relative to soybean meal and are discussed next.

Fermentation uses selected microorganisms to break down complex compounds, improving nutrient availability, reducing ANFs, and enhancing the functional properties of legumes. It also extends shelf life and improves sensory quality, making it a promising valorization strategy for underutilized crops such as cowpeas (Emkani et al., 2023). Although cowpea-specific data remain limited, extensive evidence from lentils, marama beans, soybeans, and other pulses (Table 3) provides a strong rationale for its application. Fermentation relies on GRAS-certified lactic acid bacteria (LAB), yeasts, and fungi (e.g., Lactobacillus, Rhizopus, Aspergillus, Pleurotus). These microbes secrete enzymes, cellulases, amylases, tannases, and proteases that hydrolyze macronutrients and phytochemicals, thereby lowering phytate and tannin levels, improving mineral bioavailability, and increasing free amino acids and bioactive peptides (Verni et al., 2019; Asensio-Grau et al., 2020). Fermentation is typically carried out as solid-state (SSF), submerged (SmF), or anaerobic (AF) processes, each offering distinct advantages.

Sprouting, also referred to as germination, is a cost-effective and biologically driven valorization strategy that involves the activation of the embryonic axis in viable seeds under controlled environmental conditions, typically involving optimal moisture, temperature, and aeration (Sibian et al., 2017). This process is initiated through imbibition, whereby the seed absorbs water, triggering enzymatic and metabolic changes that culminate in visible morphological changes such as radicle protrusion and the loosening or rupture of the seed coat. When applied to legume grains intended for food or feed, these biochemical transformations can enhance nutritional quality, improve digestibility and functional properties, and concurrently reduce ANFs (Atudorei et al., 2021) as shown in Table 4. While relatively underexplored in cowpeas, available evidence from cowpeas and related legumes demonstrates consistent improvements across multiple quality indicators.

Sprouting is widely reported to increase crude protein, EAAs, and vitamin content. In cowpeas, Lubisi et al. (2023) documented an increase in crude protein from 258 g/kg to 291 g/kg post-germination. Amino acid profiling revealed improvements in most AAs, although tryptophan and serine declined. In grass pea, Arshad et al. (2023) found that protein content increased from 22.6 to 30.7%, and fiber rose from 15.1 to 19.4%, while carbohydrate content dropped from 59.1 to 46.0%, suggesting nutrient concentration due to storage reserve mobilization. Sprouting also boosts micronutrient density. El-Safy et al. (2013) reported increased iron, zinc, sodium, and magnesium levels following sprouting in lentils, chickpeas, and faba beans. Sprouted legumes were also richer in riboflavin, thiamine, choline, pantothenic acid, and vitamin C (El-Safy et al., 2013; Trugo et al., 2000). These improvements are attributed to enzyme activation (e.g., phytase, amylase, protease, lipase), which degrades storage compounds, liberates micronutrients, and supports enhanced protein digestibility (Mubarak, 2005; Arshad et al., 2023). With regards to ANFs, Nagessa et al. (2023) demonstrated that phytate levels declined by 22.6 and 34.9%, and tannins by 59.4 and 66.7% after 24 and 48 h of black bean germination. Similarly, Mubarak (2005) reported a 91% reduction in phytic acid, alongside reductions in stachyose, raffinose, trypsin inhibitors, and haemagglutinins in mung beans. In pigeon pea, trypsin inhibitors decreased from 573.1 to 308.8 UTI/g, a 46% reduction (Wisaniyasa et al., 2015). In El-Safy et al. (2013) study, prolonged germination (4 days) further reduced ANFs compared to 2-day treatments. In finger millet and kidney beans, Mbithi-Mwikya et al. (2000) noted increases in sulfur-containing AAs with only minimal lysine loss in kidney beans.

Sprouting alters several techno-functional properties, some positively and others negatively. Ghavidel and Prakash (2006) observed increases in WAC and OAC in cowpeas. Similarly, Wisaniyasa et al. (2015) reported 15.7 and 14.8% increases in WAC and OAC of pigeon peas. Benítez et al. (2013) observed a reduction in resistant starch and total fiber, improving starch availability. They also noted enhancements in gelation properties, WAC, and OAC, though emulsification and foaming capacities were reduced, likely due to proteolytic degradation affecting surface-active proteins. These changes in WHC, OAC, and gelation properties are largely driven by the enzymatic remodeling of seed macromolecules during germination (Ghavidel and Prakash, 2006). Activation of endogenous proteases and amylases partially hydrolyzes storage proteins and starch, exposing additional polar and hydrophobic sites that enhance water and oil binding (Wisaniyasa et al., 2015). Concurrent degradation of cell-wall polysaccharides and the loosening of seed microstructure further improve swelling and dispersibility, which together account for the observed improvements in texture-related properties (Benítez et al., 2013).

The reported nutritional and functional effects of sprouting are strongly influenced by species, germination time, soaking regimes, light exposure, and temperature. For instance, Trugo et al. (2000) observed divergent protein retention in black beans, lupins, and soybeans when germination was combined with heat treatment. Germination under light vs. darkness (El-Safy et al., 2013) or different soaking temperatures (Wisaniyasa et al., 2015) yielded distinct effects on swelling, digestibility, and protein solubility. Lysine loss in kidney beans but not in finger millet (Mbithi-Mwikya et al., 2000) illustrates genotype-dependent responses.

The information in Table 4 indicates that sprouting is a biologically driven valorization strategy that consistently improves the nutritional, bioactive, and functional profile of legumes, including cowpeas. It enhances protein content and digestibility, amino acid profiles, and mineral bioavailability, while significantly reducing ANFs such as phytates, tannins, and enzyme inhibitors. These effects are underpinned by the activation of endogenous enzymes and compositional remodeling during germination. Although impacts on functional properties such as WAC and emulsification are sometimes mixed, sprouting remains a potent and accessible method for improving cowpea value. However, optimization must consider species-specific and condition-dependent outcomes to ensure maximal nutritional and functional gains.

While only a few studies have directly examined sprouting in cowpea, the available evidence, such as the increases in crude protein and mineral content and the reductions in trypsin inhibitors and phytate reported by Lubisi et al. (2023), indicates clear nutritional benefits. Extrapolating from related legumes, sprouting of cowpea seeds is also likely to enhance bioactive compound release, improve amino-acid availability, and increase mineral bioaccessibility through activation of endogenous phytases and proteases. These changes could expand cowpea’s potential in both animal feed and human food applications by improving digestibility, flavor, and functional properties of cowpea-based ingredients. Future research focusing on the optimization of germination time, temperature, and light exposure for cowpea is, therefore, warranted.

The thermal processing techniques, such as dry roasting, boiling, toasting, and microwaving, have gained prominence due to their practicality and proven ability to enhance the nutritional value and shelf life of legume grains used in food and feed systems. These methods are particularly beneficial in regions with short growing seasons or limited access to advanced storage infrastructure, as they facilitate microbial inactivation, moisture reduction, and the prevention of insect infestation (Cerma and Yu, 2023; Irondi et al., 2019). In low-resource settings, thermal treatments allow seasonal legume harvests to be preserved and utilized throughout the year, particularly as animal feed. Heat treatments, however, can also compromise the bioavailability of certain heat-sensitive nutrients. For instance, Irakli et al. (2020) reported reductions in vitamin E during rice bran stabilization via infrared radiation, dry heating, and microwaving, likely due to oxidative degradation. Similarly, Asunni et al. (2024) observed a decline in total mineral content in African locust bean (Parkia biglobosa) when irradiation was combined with cooking, attributed to leaching of soluble minerals into the cooking water.

Mechanical processing involves the application of physical force or machinery to cut, separate, or reshape food components, and is widely used to improve the quality, digestibility, and functionality of legume grains (Abd El-Hady and Habiba, 2003). Among the most common mechanical processing techniques applied to legumes are dehulling and extrusion (Alonso et al., 2000). Of these, extrusion, a high-temperature, short-time processing method involving the passage of material through a die using heat, pressure, and moisture, has been extensively adopted for its capacity to enhance the nutritional and functional attributes of feed ingredients (Osen et al., 2015). Extrusion modifies legume matrices through the gelatinization of starch, denaturation of proteins, and depolymerization of structural polysaccharides such as cellulose, hemicellulose, and lignin. These transformations enhance nutrient accessibility and promote digestibility. For example, Alonso et al. (2000) demonstrated that extrusion increased the WHC and water solubility index (WSI) of peas and kidney beans, while reducing their OAC. This reduction in OAC is attributed to protein denaturation and starch gelatinization, which reduce the porosity of the extrudate and limit oil-binding sites (Kesselly et al., 2023). Extrusion has also been shown to significantly alter pasting properties, as observed by Lopes et al. (2012), due to disrupted starch granules and enhanced enzyme accessibility (Mitrus et al., 2023). Martin et al. (2021) reported that the enhanced WHC and WSI of extruded legumes are directly linked to structural modifications that increase solubility and improve functionality in feed formulations.

Another benefit of extrusion is its ability to reduce ANFs. Abd El-Hady and Habiba (2003) and Lopes et al. (2012) found that soaking followed by extrusion markedly decreased levels of trypsin inhibitors, α-amylase inhibitors, and haemagglutinins in peas, chickpeas, faba, and kidney beans. Similarly, Pasqualone et al. (2020) reported the inactivation of ANFs through starch gelatinization and protein denaturation. However, nutrient losses may occur: Jeunink and Cheftel (1979) found that lysine residues in soybeans and field peas became chemically unavailable post-extrusion, potentially compromising protein quality.

Extrusion also influences protein conformation. Jiang et al. (2024) and Osen et al. (2015) noted that extrusion enhances protein solubility by disrupting structural bonds. However, under high-moisture extrusion, solubility may decrease due to protein aggregation, disulfide bond formation, and non-covalent interactions. This was supported by Osen et al. (2015), who observed reduced solubility in pea protein isolates subjected to high-moisture conditions. Additionally, Gall et al. (2005) reported that heat-induced extrusion increased the hydrolysates of legumin and convicilin, while reducing albumin, possibly due to protein aggregation and cross-linking via disulfide bridges. Importantly, extrusion outcomes are strongly influenced by processing conditions. Alonso et al. (2000) demonstrated that the protein solubility of extruded peas and kidney beans increased when treated with chemical buffers such as mercaptoethanol (2-ME) or sodium dodecyl sulfate (SDS). In contrast, solubility declined in samples not treated with these buffers, underscoring the impact of extrusion-induced protein aggregation and the need for post-processing modification.

In summary, extrusion presents a promising mechanical valorization strategy for cowpeas by reducing ANFs, improving digestibility, and enhancing functional properties such as water solubility capacity and WHC. These improvements stem from thermo-mechanical disruption of cellular structures and macromolecules. However, extrusion conditions, particularly moisture, temperature, and residence time, must be carefully optimized to maximize nutritional benefits while minimizing undesirable changes, such as reduced amino acid availability or protein insolubility. As such, extrusion can be effectively integrated into cowpea-based feed processing systems if formulation and processing parameters are tailored to preserve nutrient integrity and functional value.

Enzymatic hydrolysis has emerged as a targeted and adaptable approach to valorize legume proteins, with demonstrated improvements in protein recovery, functional properties, and bioactivity as shown in Table 5. For instance, Perović et al. (2022) achieved ~90% protein recovery from defatted chickpeas using arabinofuranosidase and cellulase+xylanase, outperforming conventional alkaline extraction by >25%. This was attributed to cell wall polysaccharide degradation, which also improved WHC, OAC, emulsifying activity, foaming capacity, and antioxidant activity. Protease-assisted hydrolysis using enzymes such as pepsin, trypsin, alcalase, and flavourzyme has further enhanced protein solubility and emulsification in faba beans, cowpeas, lentils, and pigeon peas (Eckert et al., 2019; Segura-Campos et al., 2012; Xu et al., 2021). Alcalase hydrolysates, for example, exhibited superior antioxidant and oxygen radical absorbance capacity, while bromelain-treated samples showed improved DPPH and NO radical scavenging. Sequential enzyme systems have demonstrated synergistic benefits. For example, pepsin–pancreatin hydrolysates of lima beans yielded low-molecular-weight peptides with ACE inhibitory activity and enhanced functional attributes (Polanco-Lugo et al., 2014). Similarly, Betancur-Ancona et al. (2014) reported that alcalase–flavourzyme combinations improved nitrogen solubility and foaming/emulsifying properties in French beans.

However, limitations remain, for example, enzyme–substrate specificity can lead to reduced solubility, as seen in chickpea hydrolysates (Dent et al., 2023), and hydrolysis beyond 5% DH may compromise IVPD and essential amino acid profiles (Goertzen et al., 2020). Furthermore, inhibitory effects on pancreatic lipase (Moreno et al., 2020) raise caution regarding unintended bioactivity. Overall, enzymatic valorization offers a potent avenue to enhance cowpea utilization by improving protein yield, techno-functionality, and health-related properties. Yet, outcomes are highly enzyme- and genotype-dependent, necessitating optimized and potentially combined processing strategies for broader feed and food applications.

The evidence presented in this section suggests that no single valorization method is universally superior for cowpea; the optimal approach depends on the intended application. Fermentation, particularly solid-state for protein enrichment or anaerobic for methionine enhancement, offers the most comprehensive reduction of antinutritional factors and is well-suited for high-protein feed or functional food ingredients. Sprouting is inexpensive and biologically driven, making it attractive for small-scale or household applications where improved mineral bioavailability and moderate protein gains are desired. Thermal treatments such as roasting or boiling provide rapid antinutrient inactivation and are practical for both feed manufacturing and human food preparation, although careful control is needed to avoid losses of heat-sensitive amino acids. Mechanical methods like extrusion excel when improved texture, solubility, and shelf life are priorities for feed pellets or protein concentrates, while enzymatic treatments allow precise modification of protein functionality and bioactive peptide release for specialized food or nutraceutical products. Because cowpea is used across diverse feed and food systems, tailoring the method, or combining complementary techniques, to match the target product will yield the greatest nutritional and economic benefits.

Valorization methods, including fermentation, sprouting, thermal and mechanical treatments, and enzymatic hydrolysis, consistently enhance the functional quality of cowpeas while reducing antinutritional factors. Fermentation, particularly solid-state and anaerobic approaches, improves protein digestibility, enriches sulfur-containing amino acids such as methionine, and increases water-holding and oil-absorption capacities, making fermented cowpea flours suitable for high-protein feed and functional foods. Sprouting offers a low-cost route to higher protein content, greater mineral bioavailability, and better gelation and binding, desirable for bakery and snack applications. Thermal processes such as roasting or microwave heating effectively inactivate trypsin inhibitors and lectins and improve texture and shelf life, though excessive heat can diminish heat-labile amino acids. Mechanical methods like extrusion enhance dispersibility, solubility, and shelf stability for pelleted feeds and protein concentrates, while enzymatic hydrolysis precisely tailors protein solubility and generates bioactive peptides for nutraceutical or premium food ingredients.

The optimal technique depends on the intended product. Solid-state fermentation or dry roasting is well-suited to animal-feed formulations that require maximum antinutrient reduction, whereas sprouting or controlled enzymatic hydrolysis better preserves delicate nutrients and texture for human foods. Combinations, such as sprouting followed by extrusion, can further improve nutritional quality and techno-functional performance. Among these options, enzymatic hydrolysis and extrusion show particular promise for narrowing the functional gap between cowpea and soybean meal, enhancing solubility, emulsification, foaming, and hydration properties that enable broader use in industrial feed and food systems. However, variability across cowpea genotypes, enzyme systems, and processing conditions complicates standardization and scalability. In vivo feeding trials and economic assessments, especially for enzyme-based methods, remain limited, restricting confident translation from laboratory findings to practical applications.

In summary, functional parity between valorized cowpeas and conventional protein sources appears achievable through optimized processing. Future research should prioritize genotype-specific protocols, a deeper understanding of protein structure–function relationships, validation through animal feeding trials, and integration of enzymatic, thermal, and bioprocessing strategies to maximize synergistic benefits for sustainable feed and food development.

Further studies are needed to optimize valorization protocols and assess their efficacy across diverse cowpea cultivars and non-ruminant species. In particular, controlled feeding trials should be conducted to evaluate the effects of valorized cowpeas on growth performance, nutrient utilization, gut health, and product quality in broilers, pigs, and other monogastrics. The development of multi-enzyme blends specifically targeted at cowpea ANFs, along with investigations into synergistic processing combinations (e.g., soaking followed by fermentation or enzyme treatment), should be prioritized. Additionally, the bio-efficacy of cowpea-derived bioactive compounds in promoting animal health and productivity deserves greater research attention.

To support the mainstreaming of cowpeas in animal nutrition, public and private stakeholders should invest in the development and dissemination of low-cost, scalable valorization technologies suited to rural and peri-urban feed processing contexts. Breeding programs should prioritize cowpea varieties with improved protein content, reduced ANFs, and higher digestibility. National extension services and feed industry stakeholders should promote awareness and knowledge transfer to enable smallholder farmers and feed manufacturers to adopt cowpea-inclusive diets. Moreover, policy frameworks should incentivize the use of locally produced feed ingredients to reduce import dependency and enhance feed sovereignty.

Cowpea valorization aligns with broader goals of building climate-smart, nutrition-sensitive, and economically resilient food systems. Efforts to integrate cowpeas into animal feeding strategies should be embedded within national food security and agricultural sustainability agendas. Interdisciplinary collaboration among crop scientists, animal nutritionists, food technologists, and policymakers will be essential to realize the full potential of cowpeas as a strategic feed resource. With targeted investment, innovation, and coordinated action, cowpea valorization could play a transformative role in enhancing protein self-sufficiency and strengthening sustainable livestock production in the Global South.