Despite the nutritional benefits of legumes discussed above, the consumption and utilization of legumes can be limited by the presence of several antinutritional compounds (ANCs), such as lectins, tannins, raffinose, phytic acid, trypsin inhibitors, and saponins (Kumar et al., 2010; Carbonaro et al., 2015; Yacout, 2016; Boukid et al., 2019). ANCs can generally be categorized in different ways, based on their physical characteristic, specific action, chemical structure, and biosynthetic origin. They include organic acids, such as phytic acid, glycosides (saponins), proteins or peptides, such as lectins and proteinase (trypsin and chymotrypsin) inhibitors, as well as polyphenols, such as tannins (Affrifah et al., 2023). Protein and non-protein origins are other categories into which these ANCs can be divided. Phytic acid, tannins, raffinose family oligosaccharides, saponins, vicine, and alkaloids are examples of non-protein origins, while enzyme (α-amylase, trypsin/chymotrypsin) inhibitors, lectins, and acrylamide are examples of typical protein origin (Carbonaro et al., 2015). As a natural constituent of plant-based food, ANCs have adverse effects on conventional nutrient intake (Soetan and Oyewole, 2009), limiting nutrient availability and resulting in the under-utilization of such nutrients (Yacout, 2016). They also interfere with nutrient absorption, like minerals and amino acids, leading to undesirable and toxic effects (Carbonaro et al., 2015). For example, phytic acid retards protein absorption, inhibits important digestive enzymes like trypsin, amylase, and pepsin, and obstructs the absorption of elements like calcium, iron, zinc, and magnesium (Carbas et al., 2021). Legumes contain high phytic acid level (Kumar et al., 2010), with grass peas having 8.65–17.00 mg/g, whereas lentils have 4.50–9.30 mg/g. They are also rich in α-galactosides, an oligosaccharide of the raffinose family (Grela et al., 2017).

The reduction of ANCs in legumes improves their nutritional value and overall digestibility. This reduction can be achieved through various processing methods, such as fermentation, cooking, extrusion, microwave cooking, pressure cooking, sprouting, germination, autoclaving soaking, and dehulling (Popova and Mihaylova, 2019; Samtiya et al., 2020; Wiesinger et al., 2022). A combination of these processes tends to be productive in eliminating or lowering of the ANCs. In addition to reducing ANCs, these processing methods can also inactivate them. Most of the ANCs are heat labile; therefore, they are usually removed or their possible negative effects are significantly reduced by thermal treatment. However, the heat-stable phytic acid, saponin, and tannin can be reduced by soaking, fermentation, dehulling, and sprouting (Muzquiz et al., 2012). Soaking was reported by Samtiya et al. (2020) to be the preferred method of removing ANCs from food as a result of their water solubility and subsequent loss through leaching. In addition, it facilitates seed germination, which triggers the release of phytase that aids in the breakdown of phytate. The loss of ANCs increases with an increase in soaking temperature. Legumes can be soaked in a solution of distilled water, brine, or 1% NaHCO₃ (Popova and Mihaylova, 2019). Apart from soaking, fermentation also decreases the ANCs (oxalates, phytic acid, and hydrogen cyanides) of breadfruit and cowpea. The use of thermal treatments in reducing ANCs depends on the type and duration. Among the thermal treatments, autoclaving has been reported to be the most effective method for reducing phytic acid. However, microwaving and extended boiling also have significant effects in reducing the ANC content of different foods (Samtiya et al., 2020).

Traditional processes have been used in the production of gluten-free products. These include subjecting the flour to different physical treatments, ranging from simple sieving to complex hydrothermal treatments, capable of enhancing the flour’s functionality and suitability to the different gluten-free formulations (O’Shea et al., 2014; Tsatsaragkou et al., 2017). Recently, different novel approaches have emerged in the processing of gluten-free products. These approaches focused on the improvement of the product qualities, enhancement of its functionality, and shortening of processing and residence times. The selection of a processing technology depends upon specific applications and parameters, such as flour type, processing costs, required particle size, physicochemical properties of the final product, etc. (Rosell et al., 2020). To achieve the intended gluten-free product quality, the process can be used individually or in combination (Wang et al., 2017). The novel approaches include high hydrostatic pressure, sourdough technology or fermentation, extrusion, hydrothermal, cold plasma (Rosell et al., 2020), and non-conventional heating methods, e.g., ohmic heating, jet-impingement, radio frequency heating, infrared heating, dry heating, microwave (Chhanwal et al., 2019; Rosell et al., 2020). Among the non-conventional methods, hybrid heating using infrared (IR)-microwave baking has been the only method employed in gluten-free product baking (Chhanwal et al., 2019). Some other approaches that have been applied in gluten-free foods processing include gluten proteolysis, use of genetically modified wheat, frozen storage, and partial baking (Wang et al., 2017). The formulation of legume-based gluten-free food has also utilized some of these methods. Among these methods are the use of the extrusion-cooking technique (single-screw modified extrusion-cooker) in the production of rice-yellow pea-based precooked pasta (Bouasla et al., 2016) and dry fractionation in the production of legume-based pasta (yellow lentils: whole rice) (De Angelis et al., 2022).

The formulation of GFFs involves the use of numerous gluten-free ingredients and flours. These ingredients can potentially improve the technological, sensory, and nutritional properties, as well as the shelf-life of the gluten-free product (Mir et al., 2016). However, a recent report indicated that some gluten-free products currently available in the market contain higher levels of sugar, salt, and lipids and lower levels of proteins, minerals, and vitamins (Khairuddin and Lasekan, 2021). Additionally, they adversely affect the risk factors associated with cardiometabolic disease, including atherosclerosis, insulin resistance, metabolic syndrome, obesity, and serum cholesterol levels (Anania et al., 2017). Against the backdrop of a low nutritional quality of gluten-free products, research focus has been shifted to legume-based gluten-free products in recent studies. Legume flours have functional ingredients suitable for developing numerous food products, such as meat substitutes and extenders, composite mixes and doughs, snack foods, dairy products, baked products, and gluten-free products (Hill, 2022). To further enhance their uses and benefits, legumes are subjected to fermentation process to produce gluten-free products, with an improved functional, nutritional, and sensory properties, such as gluten-free faba bread (Sozer et al., 2019). Some of the legumes that have been applied in the formulation of GFFs include chickpea, cowpea, faba bean, soybean, pea, lupine, lentil, bean, and carob (Foschia et al., 2017), Brachystegia eurycoma (Irondi et al., 2021a) and Detarium microcarpum (Irondi et al., 2022) (Table 3). They have been used to produce GFFs, like extruded snacks, pasta, bread, batter, dough, cake, noodles, and many other baked products (Hill, 2022). Their use has been reported to enhance the nutrient, functional properties, and health benefits of GFFs (Didinger and Thompson, 2021; Irondi et al., 2021a,b, 2022).

The functional properties of flours impart the quality of bakery products (Hasmadi et al., 2020). In this context, legume flours have been of paramount importance for the formulation of GFFs mainly due to their functional properties, especially their water-binding capacity and solubility index (Foschia et al., 2017). Different leguminous crops have been used to produce GFFs. Inclusion of chickpea (7.8 g/100 g) has been reported to serve as an alternative shortening and emulsifier in gluten-free bread, resulting in an increase in the gluten-free bread’s volume (Aguilar et al., 2015). Also, when chickpeas flour (75%) was substituted for rice in cassava-based gluten-free bread, it enhanced the crumb texture (by 31%), overall acceptability (by 17.35%), and loaf volume (by 23.46%) of the bread (Santos et al., 2021). Chickpea, pea, lentil, and bean flours (50% incorporation each) were reported by Gularte et al. (2012) to enhance the functional characteristics of rice-based cake, increasing the specific volume from 2.7 cm/g in the control cake to 2.9 cm/g in pea and bean, and 3.2 cm/g in lentil-based cake. Batter density decreased from 1.0 in the control cake to 0.9 g/cm³ in lentils and beans, respectively. Flour of chickpea, yellow pea, and lentil (10, 20, and 30 g/100 g respectively) blended with rice for the formulation of gluten-free spaghetti-type based pasta also enhanced the pasta’s firmness (199.50–326.50 N), adhesiveness (2.48–19.28 mJ); decreased its hardness (68.81%), expansion ratio (8.39%), and lightness (18.52%) (Bouasla et al., 2017). Filipini et al. (2021) also reported that adding soybeans (2, 4, 6, 8, and 10%) in rice flour bread decreaed the bread’s specific volume by 37.96% and increased its firmness by 89.55%. Blending bean flour with rice significantly improved the dough thermo-mechanical properties and texture of gluten-free bread (Aguiar et al., 2022).

Also, legumes can impact a dough’s viscous moduli and elasticity across a variety of frequencies as reported by Sofi et al. (2020a), when chickpea (2, 4, 6, 8, and 10%) was added to rice-based noodles. The qualities of macaron produced from carob (5, 10, and 15%) and sorghum flour were also improved due to the carob flour addition (Bissar and Ozcan, 2022). Lentil (10/100 g) used in baking pizza showed pliability (4.47 N/mm²) even in the absence of hydroxypropylmethyl cellulose (HPMC) and a tendency towards retrogradation (Pasqualone et al., 2022). Carob seed flour (0.25, 0.5, 0.75, and 1%) used in the production of vegetable milk-based yogurt also demonstrated the functional importance of legumes as it served as a thickening agent, contributing to the yogurt’s stability, rheological, and viscosity characteristic, and extending its shelf-life (Froiio et al., 2020). Also, fava beans (100%) cake was reported to have an enhanced specific volume (2.74 ± 0.26 mL/g) (Andrade et al., 2018).

There are also reports on the improvement of gluten-free cereal flour’s functional properties through the incorporation of legume flours. For examples, adding Brachystegia eurycoma (1.5 and 3%) and Detarium microcarpum (1.5 and 3%) seed flour (underutilized legumes) into whole pearl millet (98.5 and 97%) flour was reported by Irondi et al. (2021a,b, 2022) to improve the physicochemical and pasting properties of the resultant gluten-free flour. Similarly, Culetu et al. (2021) reported that adding chickpeas improved the water absorption capacity of the primarily cereals flours. In a related report, Wesley et al. (2021) demonstrated that blending bean (25 and 35%) with rice flour for the production of gluten-free biscuits increased the blends peak (213.75–340.50 RVU) and final viscosity (434.25–599.25 RVU).

The typical commercially-available GFFs are deficient in some nutrients. They are characterized by high fat, carbohydrates, and low protein content (Belorio and Gomez, 2020). However, legumes, due to their nutrient profiles/properties, can improve the nutrient profile of GFFs made therefrom (Foschia et al., 2017), enhancing their nutritional quality (Carbas et al., 2021). The nutritional importance of legumes in GFFs is discussed in the following section.

Protein deficiency has been observed to be one of the bottlenecks of gluten-free products (Belorio and Gomez, 2020). However, studies have shown that using legumes to produce GFFs can enhance the protein contents of GFFs. The report of Santos et al. (2021) demonstrated that chickpeas (75%) improved the protein content (7.49 g/100 g) of gluten-free bread made with high-quality cassava flour twice as much as those containing rice flour (4.18 g/100 g). This is similar to the report of Messia et al. (2023), when legumes (peas, red lentils, lentils, chickpeas - 30 and 100%) were used in the production of gluten-free pasta (protein contents −10.92 - 23.97 g/100 g dw). The report of Tomic et al. (2022) indicated that gluten-free crackers produced from chickpeas (65, 80, and 100%) also had an enhanced protein level (16.5%), while gluten-free cake based on fava beans (100%) had an improved protein content of 9.04 g/100 g (Andrade et al., 2018).

There are several other reports demonstrating an improvement in the protein content of GFFs made from legumes. For example, gluten-free biscuits made from rice-beans flour blend had a protein content of 7.99–10.06 g/100 g (Wesley et al., 2021). Gluten-free cake made from rice-bean composite flour had a protein content in the range of 2.69–3.45 g/100 g (Bassinello et al., 2020). Aguiar et al. (2022) also reported that incorporating bean flour in rice-based gluten free bread led to an increase in the bread’s protein contents (Aguiar et al., 2022). Furthermore, compared to spaghetti made from rice, adding beans (20 and 40%, w/w) increased the protein content of the rice-based spaghetti (10.2–14.3%) (Giuberti et al., 2015). The protein content of gluten-free pasta made from rice (8.25 g/100 g db) was also enhanced with the incorporation of different proportions (10, 20, and 30 g/100 g, respectively) of yellow peas (10.23–12.78 g/100 g db), chickpeas (9.68–9.99 g/100 g db), and lentil (10.25–13.95 g/100 g db) (Bouasla et al., 2017). Gluten-free noodles, comprising chickpea, soya, quinoa and buckwheat flours had a higher protein level (194.2 g/kg) compared to other gluten-free noodles, as well as the wheat flour control noodle (Bilgiçli, 2013). The protein contents of rice-based gluten-free couscous were also significantly improved due to field beans, chickpeas, and lentil addition at a proportion of 90/10 or 70/30%, w/w (Boudouira et al., 2023).

Substitution of soybean flour (2, 4, 6, 8, and 10%) for rice flour in rice-based gluten-free bread showed a comparable trend, with the 10% substitution increasing the protein content by 85.2% in comparison to the control bread made entirely of rice (Filipini et al., 2021). Likewise, supplementing 50% of each of the following legume flours: beans, lentils, chickpeas, and peas, raised the available protein (6.8–7.3 g/100 g) and total protein (8.7–9.4 g/100 g) of rice-based cake (Gularte et al., 2012). Additionally, Hajas et al. (2022) reported that the lentil cookies (100%) had a higher crude protein content (12.1–14.8 g/100 g) relative to the rice cookie (3.8 g/100 g). The protein content (4.4 g/100 g) of rice-based pizza also increased (7.3–7.4 g/100 g), when supplemented with lentils (10/100 g) (Pasqualone et al., 2022). In the same vein, the protein content of muffins prepared with 80:20, 65:35, and 50:50 legume-waxy rice combinations increased (6.4–9.0%) as the proportion of legume flour (50, 65, and 80%, respectively) increased (Jeong et al., 2020). Most studies showed that adding legumes to the GFFs increased their protein content more than other nutrients, such as carbohydrates, minerals, and lipids. This supports the idea that the primary component of legume crops is protein (Foschia et al., 2017; Carbas et al., 2021; Skendi et al., 2021; Messia et al., 2023). Leucine, tryptophan, valine, and methionine are a few of the essential amino acids that can be obtained from legumes used in GFFs, as observed in sorghum-based biscuits supplemented with white bean (10, 20, 30, 40, and 50%) (Ibrahim, 2017).

Studies have shown that legumes’ inclusion in the formulation of GFFs increases the GFFs’ mineral content. The report of Boudouira et al. (2023) showed that field bean, chickpea, and lentil (at 10 and 30% addition levels) enhanced the ash contents of rice-based gluten-free couscous. This suggests an increase in the mineral concentration because higher ash contents correspond to higher mineral concentrations (De Angelis et al., 2022). Muffins prepared with legume-waxy rice combinations (80:20, 65:35, and 50:50) exhibited a high level of crude ash (1.9–2.2%) as the proportion of legume flours (50, 65, and 80%) increased (Jeong et al., 2020). Chickpeas, peas, and lentils added at 50% level in rice cake increased the cake’s mineral content (15–22.72%) (Gularte et al., 2012). Beans have also been reported to enhance the ash contents of rice and bean bread (Aguiar et al., 2022), as well as biscuits (3.81–5.09 g/100 g) made with rice and bean (75:25 and 75:35) (Wesley et al., 2021). It also enhanced the ash contents of rice-based spaghetti (0.8–1.4%) relative to 100% rice (0.4%) (Giuberti et al., 2015).

The addition of soya and chickpea flours at 25% level in gluten-free noodles formulated with pseudo-cereal and cereal composite flour (buckwheat and quinoa) was reported to increase the magnesium (Mg) (945.02–1661.78 mg/kg), iron (Fe) (40.90–56.29 mg/kg), calcium (Ca) (1495.23–1562.85 mg/kg), potassium (K) (8526.15–10295.21 mg/kg), and phosphorus (P) (3755.15–5042.88 mg/kg) contents of the noodles (Bilgiçli, 2013). The addition of 45 and 70% of beans to a rice-based cake also increased the Ca content of the cake (108.63–123.39 mg/100 g) compared to the 6.55 mg/100 g Ca observed in 100% rice cake (Bassinello et al., 2020). Similarly, chickpea (100%) gluten-free crackers displayed a significant amount of ash (2.47%) and minerals, such as Mg (103 mg/100 g), K (926 mg/100 g), Na (810 mg/100 g), Ca (32.4 mg/100 g), Zinc (3.00 mg/100 g) and Fe (4.02 mg/100 g) (Tomic et al., 2022). Chickpea flour (75%) blended with 25% potato and cassava flour, respectively, to produce a gluten-free bread also improved the bread’s total mineral concentration (Santos et al., 2018). In another report, chickpeas (4.5, 9.5, and 14.5%) addition also increased the mineral content (22.22–33.72%) of a maize-based GFF spaghetti (Padalino et al., 2014).

Legumes have been reported to enhance other important nutritional indices in GFFs. It was observed that adding beans to gluten-free spaghetti increased (27.5–30.2%) its resistant starch content relative to 100% rice (11.2%) (Giuberti et al., 2015). It also enhanced the energy value (386.67–397.56 Kcal) and riboflavin (0.13–0.14 mg/100 g, relative to 0.05 mg/100 g in wheat cake) in bean and rice composite cake (45/55, 60/40 and 75/25%, respectively) (Bassinello et al., 2020). Furthermore, soybean contributed significantly to the lipid contents (1.03–5.31%) of a gluten-free bread, accounting for the high caloric value (396.51–417.11 kcal/100 g), relative to the control bread (395.01 kcal/100 g) (Filipini et al., 2021). The lipid content of rice-based gluten-free couscous was also enhanced by the incorporation of 10 and 30% field bean, chickpea, and lentil (Boudouira et al., 2023), as well as gluten-free noodles supplemented with 25% each of chickpeas and soya flour (21.0–81.2 g/kg) (Bilgiçli, 2013). Likewise, 100% chickpea crackers displayed a high amount of unsaturated fatty acid, particularly α-linolenic acid (0.77%) than crackers containing pumpkin (Tomic et al., 2022).

The formulation of GFFs has gone beyond mimicking gluten or serving as an alternative to wheat food. The increase in their demand has also been attributed to consumers’ quest for healthy food, management of CD symptoms, as well as some cases of nutrition-related non-communicable diseases (Parenti et al., 2020; Culetu et al., 2021; Irondi et al., 2022). Apart from being an excellent source of nutrients, legumes have also been reported to be rich in phytochemicals, which contribute to their health benefits (Didinger and Thompson, 2021). Legumes in GFFs have been shown to have nutraceutical/health-promoting properties, according to various studies (Gularte et al., 2012; Padalino et al., 2014; Santos et al., 2018; Sofi et al., 2020a; Santos et al., 2021; Irondi et al., 2022), some of which are presented in the following section.

Legumes have been reported to be a good source of dietary fibre in GFFs. Notably, the total dietary fiber content of the gluten-free spaghetti made from maize was increased by 38.44–42.98%, when chickpeas (4.5, 9.5, and 14.5%) were added (Padalino et al., 2014). The substitution of chickpea flour with rice in cassava flour-based gluten-free bread increased the total dietary fibre from 2.89 g/100 g to 7.21 g/100 g (Santos et al., 2021). Furthermore, the insoluble fiber (2.52 g/100 g db) and soluble fiber (0.69 g/100 g db) of a gluten-free pasta made from rice improved with the addition (10, 20 and 30 g/100 g) of yellow peas (insoluble fiber: 3.20–4.30 and soluble fiber: 1.11–1.44 g/100 g db), chickpeas (insoluble fiber: 3.65–5.15 and soluble fiber: 1.43–4.25 g/100 g db), and lentils (insoluble fiber: 2.66–3.69 and soluble fiber: 1.09–1.70 g/100 g db) (Bouasla et al., 2017). Bean flour (45, 60, and 70%) increased the total (4.47–6.49 g/100 g), soluble (1.09–1.72 g/100 g) and insoluble (3.38–4.77 g/100 g) dietary fibre contents of rice-based cake (Bassinello et al., 2020). It also enhanced the total dietary fibre of rice-based gluten-free bread (Aguiar et al., 2022). Similarly, there was also an increase in the total dietary fibre (4.35–21.43%), when chickpeas, peas, and beans flours were blended (50% each) with rice for the production of a gluten-free cake (Gularte et al., 2012). Dietary fibres are essential in promoting bowel function, rendering a laxative effect, and reducing osteoporosis risk (Barcenas and Rosell, 2006). They are also well-known for preventing colon cancer, type 2 diabetes, coronary heart diseases, and constipation (Hu et al., 2011). Hence, adding legumes, as a rich source of dietary fibre, in GFFs may contribute to reducing these diseases.

Legumes have been reported to exhibit antioxidant activity in GFFs, thereby giving them the potential to protect the body from chronic diseases associated with oxidative stress, as well as protecting the cellular molecules, such as protein, nucleic acid, and lipids, from free radicals-induced oxidative damage (Irondi et al., 2018, 2022). The antioxidant activity imparted by legumes in GFFs is ascribed to their bioactive constituents, among which phenolic compounds have been suggested to offer a superior antioxidant action (Sethiya et al., 2014; Irondi et al., 2022, 2023a). Phenolic compounds exhibit their characteristic antioxidant activity via diverse mechanisms, such as singlet oxygen suppression, chain auto-oxidation reactions disruption, transition metal ions chelation, lipid radicals formation inhibition, hydrogen peroxides reduction to produce stable compounds, endogenous pro-oxidative enzymes inhibition, and endogenous antioxidant enzymes activation (Sęczyk et al., 2019; Irondi et al., 2023b).

The study of Sofi et al. (2020a) showed that the addition of chickpeas (2, 4, 6, 8, and 10%) increased the antioxidant activity of rice-based noodles (22.6 to 31.3%). Chickpea crackers (100%) also displayed antioxidant activity (8.0 trolox mM/g) and phenolic content (0.72 mg/g) (Tomic et al., 2022). Germinated chickpea flours (5, 10, 20, and 30 g/100 g) were shown to enhance the antioxidant activity (22.8–34.5 g/100 g) and total phenolic content (TPC) (117.7–203.04 mg GAE/100 g) in pregelatinized rice flour gluten-free noodles (Sofi et al., 2020b). Similarly, lentils (10/100 g) used in rice pizza provided anthocyanins (4.36–16.29 mg/kg), in addition to enhancing the total carotenoid (25.56–29.51%), antioxidant activity (20.74–24.65%) and phenolic (0.74–0.90 mg/g) (Pasqualone et al., 2022). Furthermore, gluten-free tarhanas produced from whole flour of red, yellow, and green lentils had better antioxidant activities (19.07–39.87 μmol TE/100 g) than wheat flour tarhana (10.93 μmol TE/100 g) (Goencue and Celik, 2020). Also, lentil flour (raw and germinated) cookie displayed more antioxidant activities than a wheat flour cookie due to their high TPC (167.6–190.2 mg GA/100 g), including 1-diphenyl-2-picrylhydrazyl free-radical (DPPH^•) (4.9–5.7 mmol Trolox/kg) and 2, 2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺) (8.5–10.5 mmol Trolox/kg) radical-scavenging activity than wheat flour cookies (117.5 mg GA/100 g, 2.6 and 4.8 mmol Trolox/kg, respectively) (Oskaybas-Emiek et al., 2021). The use of different varieties of lentils (brown, red, yellow, green, and black) in baking gluten-free cookies also displayed superior antioxidant activities (0.60–1.81 mmol TE/100 g) and TPC (136.5–342.3 mg gallic acid equivalent/100 g) relative to rice cookies (0.35 mmol TE/100 g and 61.5 mg gallic acid equivalent/100 g, respectively) (Hajas et al., 2022).

The use of legumes in the formulation of GFFs has also been recommended to have the potential to manage diabetes mellitus due to their anti-hyperglycemic activity. The substitution of sweet detar flour (Detarium microcarpum) at 1.5% level in whole pearl millet flour to produce a gluten-free bread resulted in a more potent inhibition of starch-digesting enzymes (α-amylase and α-glucosidase) activity and high TPC (7.70 GAE mg/g) in the blend than the native pearl millets flour (1.90 GAE mg/g) as reported by Irondi et al. (2022). Also, chickpea-cassava (75:25) gluten-free bread had a reduction in the glycemic index (GI) (by 21%) and glycemic load (by 49%) compared to the rice-cassava (75:25) gluten-free bread (Santos et al., 2021). There was also a decrease in the in vitro starch digestibility and GI (70.8 to 61.0) of gluten-free rice noodles as the level of chickpea incorporation increased (2, 4, 6, 8, and 10%) (Sofi et al., 2020a). Gularte et al. (2012) also reported a reduction in the estimated GI (79–69) of rice-based gluten-free cake due to a 50% incorporation of chickpeas, peas, lentils, and beans.

Chickpea (4.5, 9.5, and 14.5%) has also been shown to decrease available carbohydrates (84.80–79.11 versus 87.11 g/100 g) in gluten-free spaghetti produced from chickpeas and maize (Padalino et al., 2014). The level of carbohydrates in sorghum and broken rice-based gluten-free biscuits also decreased with an increased level of white bean flour (10, 20, 30, 40, and 50%) addition (Ibrahim, 2017). This is similar to the report of Filipini et al. (2021) for a gluten-free bread (0.63–16.29% decrease in carbohydrate) produced from the composite of rice and soybean (2, 4, 6, 8, and 10%).

The anti-hyperglycaemic acitivity imparted by legumes in GFFs could be attributed to their bioactive constituents, such as polyphenolic compounds and dietary fibres, which are known to exhibit anti-hyperglycaemic effect through different mechanisms. For instance, phenolic compound, such as flavonoids and phenolic acids in legumes and other food substances are prominent for their ability to inhibit starch-digesting enzymes (alpha-amylase and alpha-glucosidase) activity (Liu and Xu, 2015; Villiger et al., 2015; Irondi et al., 2019, 2021a, 2023a). Furthermore, as an important source of dietary fibres in GFFs formulation (Gularte et al., 2012; Padalino et al., 2014; Bouasla et al., 2017; Bassinello et al., 2020; Aguiar et al., 2022), they contribute to the reduction of GI (Melini et al., 2017). Fibre, at a high level in foods, functions as a filler, thereby diluting starch concentration, reducing its viscosity (Korus et al., 2017) and consequently decreasing GI. Taken together, the high protein and low carbohydrate contents, low GI, and starch-digesting enzymes inhibitory properties of legumes promote their postprandial blood glucose-reducing potential, enhancing their anti-hyperglycaemic effect (Manzoor et al., 2020; Fratelli et al., 2021; Irondi et al., 2022, 2023a).

Using legumes in GFFs formulation can also render other health benefits, such as anti-obesity and anti-hypertensive activities. For example, an increase in the potassium level of legume-containing GFFs, such as noodle (Bilgiçli, 2013), spaghetti (Padalino et al., 2014), and tarhana (Atasoy and Hendek Ertop, 2021), suggests their anti-hypertensive activity. High potassium content has been associated with helping in lowering blood pressure in the normotensive and hypertensive population, and reducing stroke and other cardiovascular diseases (Lanham-New et al., 2012). In another study, Sung et al. (2020) reported a higher angiotensin I-converting enzyme (ACE) inhibitory activity in a gluten-free rice layer cake supplemented with 10% chia seed flour relative to the control rice flour layer cake. ACE catalyzes the conversion of angiotensin I to angiotensin II in the rennin-angiotensin system, by hydrolytically cleaving a dipeptide (histidyl–leucine) from angiotensin I. The angiotensin II so-formed is a well-known active vasoconstrictor, capable of stimulating blood pressure elevation by activating aldosterone secretion and inactivating bradykinin, a vasodilator and hypotensive peptide (Eriksson et al., 2002; Irondi et al., 2018). Thus, the ACE inhibitory capacity of the gluten-free rice layer cake supplemented with 10% chia seed flour suggests its propensity to reduce high blood pressure.

GFFs have also been reported to possess anti-obesity effect. In this context, biscuits formulated from yellow maize and cowpea composite flours at different proportions were reported to inhibit pancreatic lipase activity, suggesting the biscuits’ anti-obesity potential (Irondi et al., 2021b). Jeong et al. (2020) also recommended gluten-free muffins formulated from mung bean and cowpea (50, 65, and 80%) to render health benefits due to their lower fat content (1.0–2.6%). Likewise, vegetable milk-based yogurt produced with gluten-free carob seed flour (0.25, 0.5, 0.75, and 1%) was reported to be free from bad cholesterol and lactose (Froiio et al., 2020).