Introduction

Ensuring world food security and addressing nutritional inadequacies pose significant challenges for the expanding human population. The promotion of crop diversification emerges as a crucial strategy for effectively attaining food security [1]. Changing climatic conditions have a profound impact on food security by limiting crop production. Consequently, experts in nutrition and technology must re-evaluate issues related to limited on-field production, aiming to search for appropriate crops with potential as a food source [2]. Millet is a nutritional alternative capable of fulfilling the dietary requirements of an increasing population, as suggested by Kumar et al. [3]. Millets are underutilized crops that may be cultivated in dry, hot, and humid environments where the chances of growing other crops are lesser. Sorghum (Sorghum vulgare; Jawar), pearl millet (Pennisetum glaucam; bajra) are recognized as major millets, and many other small-sized millets such as finger (Eleusine coracana; ragi), foxtail (Setaria italica, kangani), proso (Panicum miliaceum; barri), little (Panicum sumantrense), barnyard (Echinochloa utilis; sanwa) and Kodo millet (Paspalum setaceum; kodra) are minor or small millets [4]. India is the biggest producer (11,849,190 tonnes) of millets in the world, and the second producer is Niger (3,656,958 tonnes) [5]. (Fig. 1.). United Nations (FAO-UN) has been working on scaling up millet cultivation, develo** techniques for millet processing, and promoting millet consumption by the population. In fact, the year 2023 has been accepted as the International Year of Millets by FAO-UN. These plants have been recognized as “smart crops” as they help nurture the health and nutrition of the rising population, maintain the environment of the planet, and keep the agricultural system sustainable [6].

Fig. 1
figure 1

Top 10 producers of millets [5]

Full size image

Wheat, in particular, is extensively utilized in food product preparation owing to its viscoelastic characteristics. Wheat contains gluten protein, which is responsible for celiac disease, and interest in non-allergenic ingredients, the food industry drifting toward the production of gluten-free products. Compared to wheat flour, the nonglutinous nature of millet produces less elastic, cohesive, and extended dough during hydration [7]. Nevertheless, boasting an enhanced nutritional composition, millet exhibits nutraceutical qualities and is non-allergenic, providing an array of health advantages. Due to these attributes, millet could serve as a promising substitute for crafting gluten-free cuisine. Millets are a highly valuable supplementary nutritional resource for humans, owing to their rich content of essential components such as starch, B vitamins, minerals, polysaccharides (antioxidants), and dietary fibers [8]. Nutritionally, millets contain carbohydrates, fat, protein, dietary fiber, and mineral content of 60–70%, 1.5–5%, 6–19%,12–20%, and 2–4%, respectively [9]. Its proteins are an abundance of essential amino acids, excluding lysine and threonine. These grains are also good sources of micronutrients and phytochemicals [10,11,12]. These are utilized in various food products on the basis of nutrient content. Millets are used for the preparation of chapatti [13, 14], bread [15, 16], prebiotics [17], and probiotics [18], etc. Food products from wheat are more popular due to their textural and sensorial properties. In this article, the nutritional and application of millets will be explored.

Nutritional Composition

Millets are nutritionally similar to other cereal grains, i.e., wheat, rice, and corn. Millet grains (pearl millet, finger, foxtail, little, barnyard, kodo, little) that have undergone milling exhibit varying nutrient compositions. Millets contain 65–75% carbohydrates, 7–12% protein, 15–20% dietary fiber, and 2–5% fats [19]. Punia et al. [20] reported the ash, fat, and fiber contents of wheat cultivars ranged between 1.52% to 1.76%, 2.62% to 3.48%, and 0.79% to 0.93%, respectively. Millet starch content ranges from 60 to 75%, with amylopectin and amylose concentrations ranging from 16 to 28% and 72% to 84%, as well as nonstarchy polysaccharides (15–20%) and sugars (2–3%) [21]. Therefore, millet starch acts as the primary energy source in the millets. Millet proteins contain high amounts of essential and non-essential amino acids. Prolamin demonstrates a substantial presence of hydrophobic proline and glutamine, whereas the distribution of essential amino acids (EAA) is more evenly distributed in albumin and globulin. Millets proteins were reported to have a superior essential amino acid profile than maize proteins [22]. Consequently, it is deduced that the levels of EAA in millet proteins vary in accordance with the respective protein fractions [23]. Further, the uniqueness of finger millet proteins lies in their high concentration of sulfur-rich amino acids, making them valuable for creating health-focused foods and protein-rich products aimed at addressing protein deficiency disorders [24]. Lipid composition varied from 1 to 5%, comprising neutral lipids, phospholipids, and glycolipids in proportions of 85%, 12%, and 3%, respectively, as reported by Himanshu et al. [21]. Millets contain bioactive compounds primarily in the configurations of free and conjugated phenolic acids, encompassing derivatives of hydroxybenzoic and hydroxycinnamic acids [25].

Millet based Food Products

Millets are categorized as "Nutri-cereals" because of their significant protein amount, which includes balanced phytochemicals, minerals, fatty acids, carbohydrates, and amino acids. The nutritional profile of millets establishes them as a feasible option for refining and incorporating into diverse food products, specifically in the preparation of gluten-free functional foods [25].

Bakery Products

Flatbreads

Chapati, Rotti, and Rotla are common gluten-free pancake-like foods that can be formulated using hot water and unfermented pearl millet (PM) flour [13] or with fermented PM flour like Lohoh, from Saudi Arabia [27]. Adding finger millet to WF enhances the nutritional composition of flatbread (FB) while supplying potential health advantages. A research study investigated the impact of using extruded versus unextruded finger millet flour on the pasting, textural, and rheological characteristics of composite wheat dough and how they affect FB quality. Extruded finger millet (EFM) altered the handling properties of the dough, resulting in higher viscoelastic moduli and elastic compliance. Moreover, an FB made by replacing 20% WF with EFM showed improved puffing and reduced resistance, shrinkage, and baking time compared to an FB made with unextruded finger millet flour at the same substitution level. Sensory evaluations rated this FB similarly to the control whole wheat FB. The findings indicate that substituting EFM flour in composite dough maintains wheat flatbread's rheological and technological characteristics [28]. Celiac disease patients are increasing in the world day by day, and the gluten-free diet is the only solution for this. Considering health concerns, the same group Kumar et al. [29] formulated gluten-free unleavened FB with combined maize dough replaced with different amounts of extruded finger (10, 20 & 30%). The authors confirmed the significant effect of EFM flour in dough handling and formulation of FB. Further, the sensory evaluation indicated that, despite minor color alterations, the taste of the composite unleavened FB was comparable to the control (maize). The findings suggest that integrating EF flour can enhance the rheological, techno-functional, and nutritional attributes of maize-based FB. Among the various flatbreads, the FB formulated with extruded flour (FB20) attained a superior sensory score (7.8). The investigation by Sharma and Gujral [14] explored the properties of composite bread derived from a blend of refined wheat and millet flours (MF) in a ratio of 3:1. In the case of wheat millet composite flour (WMCF) flatbreads, certain flatbread characteristics, including shrinkage and bake loss (BL), exhibited a notable increase, whereas puffing and consumer acceptability experienced a decrease. It was observed that wheat bread showed the highest sensorial score compared to millet flatbread. Panghal et al. [30] determined that incorporating finger millet flour at a 20% concentration yielded dough exhibiting favorable handling characteristics and sheeting properties, ultimately producing chapattis of overall acceptable quality. FB prepared from millet are generally less accepted compared to those prepared from wheat due to differences in their sensory and textural qualities; however, the addition of millets in FB is the best method to improve the techno-functional characteristics of chapattis and increase the consumption of traditional staple millets in the population.

Bread

Bread constitutes a bakery product comprised primarily of water, flour, salt, yeast, sugar, and fat. These components undergo mixing and fermentation to generate a viscoelastic dough, subsequently subjected to baking [31]. MF possesses abundant nutritional content and exhibits viscoelastic characteristics that facilitate its incorporation into bread formulations. Nehra et al. [15] examined the properties of bread prepared from combined flours containing different amounts of wheat and PM (10, 20, 30, & 40%). The addition of PM flour increased the physical parameter of loaf weight, whereas a reverse trend was detected for loaf volume. Bread formulations with up to 30% PM flour to WF revealed an acceptable sensorial score. However, beyond this threshold, the additional incorporation of PM flour rendered the bread of unacceptable quality. Bread prepared from wheat flour showed an overall sensorial score of 7.9, whereas 5.1 to 7.1 for bread formulated from PM. The properties of bread prepared from a combination of foxtail millet and WF were investigated by Passi et al. [16]. Through the assessment of various parameters and sensory analysis, the bread ready-mix incorporating 30% foxtail millet flour was found to be the most acceptable. In a separate study, Sarabhai et al. [32] employed enzymes, specifically glucose oxidase (GO), xylanase (XYL), and protease (PR), to enhance gluten-free bread made from foxtail millet. The findings revealed that the addition of PR enzyme at 0.1 g/100 g is conducive to the preparation of foxtail millet bread, imparting improved textural and sensory characteristics. Li and colleagues [33] investigated the impact of incorporating millet bran dietary fiber (DF) into MF for the formulation of bread. It was observed that as the DF amount increased, the toughness of the resulting steamed bread rose while springiness notably declined, leading to a decrease in sensory acceptability. Krochmal-Marczak et al. [34] also studied the effect of oat flour addition on nutritional and sensorial properties. They observed that sensory scores decrease with an increase in the amount of oat flour. Figure 2 shows the pictorial representation of bread prepared from raw and precooked milled-based bread.

Fig. 2
figure 2

Millet-based bread, A 100% raw millet flour, B 100% pre-cooked millet flour, C 50% raw + 50% pre-cooked millet flour [48]

Full size image

Cookies

Cookie is derived from the Dutch word koekje, meaning "little cake [35]. The major ingredients for the formulation of cookies are flour, fat, and sugar. As observed by Sharma et al. [36], various millets, namely foxtail, barnyard, and Kodo millets, were germinated and utilized in the formulation of gluten-free cookies with blended flours. The sensory score indicated that cookies (designated as A2), formulated by incorporating germinated foxtail, barnyard, and Kodo millets in the ratio of 70:20:10, were deemed the most satisfactory. Furthermore, these cookies were characterized as having the largest nutritional value and exhibiting the required functional characteristics. The effect of PM flour on refined WF for cookie preparation was studied. It was observed that the PM cookies were satisfactory, as shown by their highest quality score [37]. Awolu et al. [38] formulated the cookies from various flour samples, including soybean, rice, millet, and tiger nut, which underwent distinct processing protocols such as fermentation, debranning, and malting. Flour blends incorporating fermented millets demonstrated the highest overall acceptability score. The findings from this research underscored the potential for enhancing both flour quality and cookies through the application of processing techniques and composite flour formulations. Hussain et al. [39] formulated cookies incorporating varying proportions of MF (0%, 25%, 50%, 75%, and 100%) in WF. The sensorial evaluation revealed that cookies containing over 50% MF were less preferred by the sensory panelists. However, the antioxidant capacity was notably higher in millet cookies compared to the control cookies (WF-100%). Wheat-pumpkin seed-based cookies were prepared by Gebremariam et al. [40]. The nutritional value of composite cookies was observed. Millet-based cookies could be formulated to enhance their nutritional profile. However, due to their lower sensorial appeal, blending MF with WF may be advisable to improve overall palatability.

Beverages

The utilization of millet in the manufacturing of plant-based beverages offers advantageous outcomes owing to its healthful attributes and gluten-free nature. In its unprocessed state, millet abounds with dietary fiber and polyphenols [41].

Probiotic and Prebiotic

Prebiotics are "non-digestible dietary components that specifically stimulate colonic bacteria to improve human health. Mondal et al. [42] documented the initial identification of a distinctive polysaccharide derived from millet, demonstrating resistance to digestion by salivary and pancreatic α-amylase. Additionally, the polysaccharide exhibited a favorable prebiotic activity score with L. acidophilus and L. brevis. Prebiotic beverage using 2% pineapple crown powder (PCP) with 1% (v/v) Lactobacillus rhamnosus GG NCDC 347 (LGG), find the optimized white finger millet probiotic beverage (OWMPB) [17]. Probiotics refer to living microorganisms employed to confer health benefits, primarily focused on the restoration of gut flora [43]. Malini et al. [18] developed, optimized and assessed the successful integration of pineapple core powder (PCP) into plant-based probiotic beverages utilizing Lactocaseibacillus rhamnosus (LGG). The optimal formulation for creating a PCP-enhanced white finger millet probiotic beverage (PAMPB) was determined as 14:5:2:2 for white finger millet, sugar, PCP, and LGG inoculums, respectively. Millets have good potential for the production of probiotic and prebiotic beverages. Finger millet is commonly utilized in beverage preparation (Table 1).

Table 1 Millet-based food products and beverages
Full size table

Alcoholic and Non-Alcoholic Beverages

Millet-derived beverages, encompassing both alcoholic and non-alcoholic varieties such as malwa, Bantu, pombe, and opaque or kaffir beer, exhibit greater prevalence in comparison to alternative products [44]. Jandh, a traditional alcohol-based drink in Nepal, is crafted through the utilization of finger millet, as documented by Tamang et al. [45]. Kunun-zaki stands as a widely consumed fermented non-alcoholic beverage formulated from maize, sorghum/millet, spices, and sugar [46]. Mbege ale, a beer crafted from a blend of millet, sorghum, and banana, has undergone industrialization, packaging, and commercialization under the name chibuku shake. This beverage maintains popularity, particularly in regions such as Botswana, Zambia, and Zimbabwe [47].

Limitations of Millets in Food Products

Millet serves as a viable alternative to wheat in food production. However, products derived from millet often face challenges in sensory acceptance. Particularly in bakery formulations, their lower viscoelastic properties compared to wheat result in decreased acceptability. Furthermore, millet-based products typically exhibit a harder texture, increased weight, and less porous structure. Moreover, the less desirable taste and flavor profile of millets constrains their application in product formulations. Additionally, millets contain a high concentration of anti-nutrients, which can hinder the absorption of essential nutrients, posing a significant concern for consumption. Proper cooking methods are crucial to mitigate these issues. Furthermore, millets contain goitrogens, compounds that can disrupt thyroid function by impeding iodine uptake, particularly in excessive quantities. Despite these limitations, millets are generally considered nutritious and offer various health benefits, including being rich in fiber, antioxidants, and essential nutrients. They can be a valuable addition to a balanced diet, especially for those seeking alternative grains or gluten-free options.

Conclusion

This review paper examines the nutritional and food applications of millet. Considering the available data on millet, it is evident that millets exhibit significant potential for various food applications. Due to their drought-resistant nature, millets can thrive in less fertile lands where other crops may struggle to cultivate. Derived from the findings of conducted studies, it is concluded that millet grains had numerous health-promoting constituents, including dietary fiber, minerals, vitamins, and phytochemicals, notably phenolic compounds. These components demonstrate comparability to those found in major grains and, concurrently, present several potential health benefits. Due to the nutritional properties of millet, these are used in the preparation of various food products. However, the textural and sensory characteristics of millet products render them less acceptable than wheat products. Further research is imperative to improve the acceptability of millet-based products. PM and finger millet are commonly utilized in food product formulations owing to their favorable taste and flavor profiles.