The increasing demand for dairy-free foods has stimulated considerable interest in plant-based alternatives to conventional fermented dairy products. Factors such as lactose intolerance, milk protein allergy, vegan dietary preferences and growing awareness of health and environmental sustainability have encouraged the development of nutritionally enriched millet-based fermented products. However, plant-based yoghurt alternatives often present technological challenges related to texture, stability, flavour and consumer acceptability because their structural characteristics differ from those of conventional dairy yoghurt. Consequently, the selection of suitable plant-based raw materials and appropriate processing strategies is essential for developing fermented products with desirable quality attributes.
       
Nutri-cereals offer considerable potential for the development of functional millet-based yoghurt because of their nutritional diversity and presence of bioactive constituents. Finger millet (Eleusine coracana) is particularly recognized for its high calcium content and phenolic compounds, while pearl millet (Pennisetum glaucum) provides protein, minerals and bioactive components. Little millet (Panicum sumatrense) contributes dietary fibre and minerals, whereas oats (Avena sativa) are an important source of soluble fibre, particularly β-glucan, together with proteins and antioxidant compounds. Combining these cereals can provide complementary nutritional and functional attributes while improving the overall suitability of the cereal matrix for value-added food applications (Leszczyńska et al., 2023; Pérez-Rodríguez et al., 2023; Saxena et al., 2023).
       
Fermentation with yoghurt cultures provides an additional benefit to improve the functionality and sensory characteristics of cereal-based products. Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus are established yoghurt starter organisms that contribute to acid development, flavour formation and structural changes during fermentation. Previous studies have demonstrated the feasibility of incorporating millet matrices into probiotic and synbiotic yoghurt-like products while maintaining favourable nutritional and sensory characteristics. Amrutha et al., (2023) reported high sensory acceptability and substantial viable populations in barnyard millet-based probiotic yoghurt, while Jayawardana et al., (2026) demonstrated the potential of finger millet incorporation in yoghurt without compromising sensory quality. These findings indicate that suitably formulated cereal matrices can serve as promising substrates for fermented millet-based yoghurt development.

Materials
 
Finger millet (Eleusine coracana), pearl millet (Pennisetum glaucum), little millet (Panicum sumatrense) and oats (Avena sativa) were selected as the major Nutri-Cereals for development of the composite plant-based substrate. Mature, clean and good-quality grains free from visible infestation, mould growth and other defects were procured from the local market of Parbhani, Maharashtra, India. The grains were manually cleaned, washed with potable water and stored in food-grade polyethylene pouches under clean and dry laboratory conditions until further use.
       
Food-grade stabilizers, sweetening and other ingredients were procured from authorized commercial suppliers. A commercial yoghurt starter culture containing Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was used for fermentation of the millet-based yoghurt. Analytical-grade chemicals and microbiological media were procured from reputed suppliers and used for the respective analyses.
 
Preparation of composite nutri-cereal substrate
 
The selected Nutri-Cereals were subjected to standardized pretreatment and extraction procedures developed during the preliminary experimentation. The individual Nutri-Cereal extracts were subsequently combined to obtain the standardized composite nutri-cereal substrate. The optimized composite substrate was further standardized with respect to total solids and incorporated with the selected stabilizer and other ingredients before yoghurt preparation.

Development of functional probiotic millet-based yoghurt
 
The standardized composite Nutri-Cereal substrate was heated at 90±2°C for 10 min under continuous stirring. The heat treatment was applied to ensure microbial safety and facilitate development of the desired textural characteristics. The heated substrate was subsequently cooled to approximately 37°C before inoculation with the yoghurt starter culture.
       
The cooled substrate was aseptically inoculated with 1% mixed yoghurt starter culture containing S. thermophilus and L. delbrueckii subsp. bulgaricus. The culture was thoroughly mixed to obtain uniform distribution throughout the substrate. The inoculated product was incubated at 37.5°C for 12 h under controlled conditions until the desired yoghurt-like gel structure and acidity were developed. Following fermentation, the product was immediately cooled to 4±1°C to minimize further acid development and stabilize the fermented matrix. The prepared yoghurt was filled into pre-sterilized food-grade containers and stored under refrigerated conditions until further analysis.
 
Physicochemical analysis
 
The developed millet-based yoghurt was evaluated for pH, titratable acidity, total soluble solids, moisture, total solids and colour characteristics using standard AOAC procedures. All measurements were carried out in triplicate. The pH was measured using a calibrated digital pH meter after stabilization of the electrode in the yoghurt sample. Titratable acidity was determined by titration against standardized NaOH using phenolphthalein as the indicator and expressed as percentage lactic acid. Total soluble solids were measured using a digital refractometer and expressed as °Brix. Moisture and total solids were determined according to standard AOAC procedures.
       
Colour characteristics were measured using a Hunter colourimeter and expressed in terms of L*, a* and b* values. The L* value represented lightness while a* and b* represented the red-green and yellow-blue coordinates respectively (Bachate et al., 2025).
 
Proximate and mineral composition
 
The proximate composition of the optimized millet-based yoghurt was determined using standard AOAC procedures. Moisture, crude protein, crude fat, crude fibre and ash were determined using standard analytical methods while carbohydrate content was calculated by difference. Mineral constituents were determined using appropriate standard procedures and instrumental methods as applicable. All analyses were performed in triplicate (Mariam and Kumari, 2024; Manasa et al., 2022).
 
Sensory evaluation
 
Sensory acceptability of the developed millet-based yoghurt was evaluated using a 9-point hedonic scale. A panel of 30 semi-trained judges comprising postgraduate students and faculty members of the College of Food Technology, VNMKV, Parbhani participated in the evaluation.
       
The samples were assigned random three-digit codes and presented to the judges in randomized order under controlled sensory evaluation conditions. The attributes evaluated included colour and appearance, flavour, taste, texture/mouthfeel and overall acceptability. The judges were instructed to evaluate each sample independently and record their degree of liking using the 9-point hedonic scale. The use of coded samples, randomized presentation and a 9-point hedonic scale was used for the sensory evaluation of millet-based yoghurt (Mariam and Kumari, 2024).
 
Determination of total dietary fibre and soluble dietary fibre
 
The total dietary fibre (TDF) and soluble dietary fibre (SDF) contents of the developed functional probiotic millet-based yoghurt were determined using the enzymatic-gravimetric method described in AOAC Official Method 991.43 (AOAC, 2023). The method involves sequential enzymatic digestion of the sample using thermostable α-amylase, protease and amyloglucosidase to hydrolyse digestible starch and proteins while retaining the dietary fibre fraction.
       
For the analysis, a representative portion of the yoghurt sample was dried and finely homogenized before analysis. The sample was subjected to sequential enzymatic treatment with thermostable α-amylase, protease and amyloglucosidase under controlled conditions. The enzymatic treatment hydrolysed starch and protein components while the non-digestible fibre fraction remained in the digestate. For determination of total dietary fibre, soluble dietary fibre was precipitated from the enzymatic digest using aqueous ethanol. The precipitated fibre was recovered by filtration and washed with alcohol and acetone. The residue was subsequently dried to constant weight and weighed.
       
For soluble dietary fibre determination, the enzymatic digest was filtered to separate the insoluble dietary fibre fraction. The filtrate containing soluble dietary fibre was treated with aqueous ethanol to precipitate the soluble fibre, followed by filtration, washing, drying and weighing. The dietary fibre residues were corrected for protein, ash and reagent blank contributions. Total dietary fibre was calculated from the corrected insoluble and soluble fibre fractions and expressed as g/100 g sample. All analyses were performed in triplicate.
 
Statistical analysis
 
The experimental data were subjected to analysis of variance (ANOVA) using IBM SPSS Statistics software. The significance of differences among treatment means was determined using Duncan’s multiple range test (DMRT) at a significance level of p<0.05. All analyses were performed in triplicate and the results were expressed as mean values with appropriate measures of variation. The statistical procedure was adopted to determine significant differences among the treatments (Duncan, 1955).

Physicochemical properties of functional probiotic millet-based yoghurt
 
The physicochemical characteristics of the developed functional probiotic millet-based yoghurt are presented in Table 1. The product showed a moisture content of 80.50±0.30%, titratable acidity of 0.86±0.04% as lactic acid, pH of 4.14±0.02, total solids of 19.50±0.50%, TSS of 17.60±0.20% and viscosity of 1325±28 cP. The obtained values indicate successful fermentation of the composite Nutri-Cereal substrate and development of a thick yoghurt-like matrix.


       
The moisture content of 80.50±0.30% corresponded to a total solids content of 19.50±0.50%. The relatively high solids concentration is desirable in millet-based yoghurt because cereal-derived starch, protein and dietary fibre contribute to body, water retention and structural development. The presence of these constituents in the composite Nutri-Cereal matrix was due to the formation of a cohesive fermented product.
       
The pH of the yoghurt was 4.14±0.02 with a corresponding titratable acidity of 0.86±0.04% lactic acid, indicating effective acid development during fermentation. The starter organisms, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, utilize fermentable carbohydrates and convert them primarily into lactic acid, resulting in a progressive reduction in pH. The obtained acidic condition is characteristic of yoghurt fermentation and contributes to flavour development and structural stabilization of the fermented matrix. Similar acidification behaviour has been reported in millet-based probiotic fermented products, confirming the suitability of millet substrates for yoghurt-type fermentation (Shruthi et al., 2025).
       
The TSS value of 17.60±0.20% indicates a substantial soluble fraction in the developed yoghurt. The soluble fraction comprise soluble carbohydrates, organic acids, minerals and other dissolved constituents derived from the composite Nutri-Cereals and formulation ingredients. The difference between total solids and TSS is expected because a proportion of cereal-derived starch, protein, fibre and other constituents remains in dispersed or insoluble form.
       
A notable characteristic of the developed yoghurt was its viscosity of 1325±28 cP. The marked viscosity indicates the formation of a structured yoghurt-like matrix during fermentation. Acidification can modify interactions among cereal proteins, starch and dietary fibre while the stabilizing components contribute to water immobilization and structural integrity. The starch and dietary fibre fractions supplied by the nutri-cereals, together with the soluble β-glucan fraction of oats, have further contributed to water binding and increased resistance to flow. Joshi et al., (2025) have similarly demonstrated that cereal incorporation can improve viscosity and textural characteristics of fermented cereal matrices.
 
Colour characteristics of functional probiotic millet-based yoghurt
 
The instrumental colour characteristics of the developed functional probiotic millet-based yoghurt are presented in Table 2. The product exhibited L*, a* and b* values of 66.95±0.31, 8.82±0.13 and 27.85±0.28, respectively. The corresponding chroma and hue angle values were 29.21±0.27 and 72.43±0.28°, indicating a moderately light and predominantly yellow-red colour characteristic of the composite Nutri-Cereal matrix.


       
The L* value of 66.95 indicates appreciable lightness of the developed yoghurt despite the incorporation of pigmented millet grains. The relatively moderate lightness was associated with the combined effect of finger millet, pearl millet, little millet and oats, together with suspended cereal solids and the structural changes occurring during fermentation. Finger millet, in particular, contains coloured phenolic compounds that can contribute to a darker appearance, whereas oats and lighter-coloured millet fractions can increase the overall lightness of the composite matrix. Similar effects of millet incorporation on yoghurt colour have been reported in recent studies where increasing millet-derived ingredients altered the L* value of yoghurt products (Vasanthakumari et al., 2025).
       
The positive a* value of 8.82±0.13 indicates a shift towards the red region, while the positive b* value of 27.85±0.28 indicates a pronounced yellow component. The relatively high b* value was associated with the inherent yellowish colour of the cereal constituents and the distribution of cereal-derived pigments within the yoghurt matrix. The positive a* and b* values together indicate that the developed product possessed a yellowish-red rather than a neutral white appearance. Similar changes in a* and b* values have been reported in millet-containing yoghurt systems and have been attributed to the natural pigments contributed by millet ingredients (Vasanthakumari et al., 2025).
       
The chroma value of 29.21±0.27 indicates moderate colour saturation, while the hue angle of 72.43±0.28° confirms the predominance of a yellow-red hue. The close relationship between the positive a* and b* values and the calculated chroma and hue angle indicates that the instrumental colour measurements were internally consistent. Colour is particularly important in millet-based yoghurt because visual appearance contributes to consumers’ initial perception and can influence product acceptability.
 
Proximate composition of functional probiotic millet-based yoghurt
 
The proximate composition of the functional probiotic millet-based yoghurt showed 80.50±0.64% moisture, 2.18±0.05% fat, 4.26±0.09% protein, 10.72±0.19% carbohydrates, 1.00 ± 0.03% crude fibre and 1.34±0.03% ash (Table 3). The relatively high moisture content is characteristic of yoghurt-type fermented products and reflects the aqueous nature of the composite Nutri-Cereal matrix. The corresponding solid fraction contributed to the nutritional and structural properties of the product. Similar moisture and total-solids ranges have been reported for plant-based yoghurt analogues developed from cereal and legume-based substrates (Elechi et al., 2023).


       
The fat content of 2.18±0.05% reflects the natural lipid contribution of the selected Nutri-Cereals, particularly oats, which has a comparatively higher lipid content than most cereal grains. The protein content of 4.26±0.09% indicates a meaningful contribution of millet-based proteins to the nutritional quality of the fermented product. Fermentation can alter the cereal matrix through microbial metabolism and enzymatic activity, thereby influencing the measurable nutritional composition. Wang et al., (2025) have similarly demonstrated the potential of millet incorporation to improve the nutritional and functional characteristics of yoghurt products.
       
Carbohydrates constituted 10.72±0.19% of the yoghurt, representing the major proximate component after moisture. This is expected because the formulation was based on carbohydrate-rich Nutri-Cereals, with starch serving as the predominant reserve carbohydrate. The crude fibre content of 1.00±0.03% demonstrates the retention of cereal-derived dietary fibre in the final fermented product. Although fermentation can modify some components of the cereal matrix, the measurable crude fibre fraction remained appreciable in the developed yoghurt. The ash content of 1.34±0.03% indicates the presence of mineral constituents originating primarily from the composite Nutri-Cereal ingredients.
 
Mineral composition of functional probiotic millet-based yoghurt
 
The mineral composition of the functional probiotic millet-based yoghurt demonstrated the presence of appreciable amounts of calcium, phosphorus, iron, zinc, potassium and magnesium (Table 4). Calcium was recorded at 52.34±1.05 mg/100 g while phosphorus was 91.75±1.48 mg/100 g. The concentrations of iron and zinc were 1.72±0.05 and 1.15±0.03 mg/100 g, respectively, whereas potassium and magnesium were present at 124.38±2.04 and 44.12±0.74 mg/100 g. The mineral profile revealed the contribution of the composite Nutri-Cereal matrix to the nutritional quality of the fermented product. Millets are recognized as important sources of minerals, although their mineral composition varies considerably according to cereal type, genotype and growing conditions (Anitha et al., 2024).


       
Among the minerals evaluated, potassium showed the highest concentration, followed by phosphorus, calcium and magnesium. The presence of iron and zinc further contributes to the micronutrient value of the developed yoghurt. Although mineral concentration alone does not establish mineral bioavailability, fermentation may influence the nutritional utilization of minerals through modification of antinutritional factors such as phytic acid. Lactic acid fermentation can promote phytate degradation through microbial and endogenous phytase activity, potentially reducing mineral–phytate interactions and improving the accessibility of minerals such as calcium, iron and zinc (Chauhan and Gujral, 2024); (Endalew et al., 2024).
 
Total dietary fibre and soluble dietary fibre of functional probiotic millet-based yoghurt
 
The functional probiotic millet-based yoghurt contained 5.24±0.14% total dietary fibre and 2.14±0.06% soluble dietary fibre (Table 5). The appreciable fibre content can primarily be attributed to the composite Nutri-Cereal matrix comprising finger millet, pearl millet, little millet and oats. Fermentation can modify the cereal cell-wall matrix and alter the extractability and distribution of fibre-associated components. The retention of appreciable dietary fibre in the developed yoghurt was because it differentiates the product from conventional dairy yoghurt, which generally contains little or no dietary fibre.


       
Soluble dietary fibre showed a comparatively greater increase than total dietary fibre, reaching 2.14±0.06% in the millet-based yoghurt. This increase may be associated with fermentation-mediated modification and solubilization of components within the cereal matrix. The presence of oats in the composite formulation is particularly relevant because oats are an important dietary source of β-glucan, a soluble dietary fibre. Consequently, the combination of oats with the selected millets provides a complementary fibre profile in the developed product.
       
The proportion of soluble fibre relative to total dietary fibre also increased from approximately 34.6% in the millet beverage to 40.8% in the millet-based yoghurt. This shift suggests modification of the fibre profile during fermentation and may contribute to the functional character of the product. However, the present study did not characterize individual fibre components or directly determine the prebiotic activity of the fibre fraction.
 
Sensory evaluation of functional probiotic millet-based yoghurt
 
The sensory evaluation demonstrated that the developed functional probiotic millet-based yoghurt was highly acceptable to the sensory panel. All evaluated attributes recorded scores above 8.0 on the 9-point hedonic scale (Fig 1). However, the conventional dairy yoghurt recorded significantly higher scores than the developed millet-based yoghurt for colour and appearance, flavour, taste, mouthfeel and overall acceptability (p<0.05).


       
The colour and appearance score of the developed millet-based yoghurt was 8.28±0.09, compared with 8.62±0.11 for the dairy yoghurt (Table 6). The slightly lower score may be associated with the characteristic cream to slightly darker appearance imparted by the composite Nutri-Cereal matrix compared with the familiar white appearance of conventional dairy yoghurt. Nevertheless, a score above 8.0 indicates that the visual characteristics of the developed product remained highly acceptable.


       
The flavour score was 8.16±0.10 for the millet-based yoghurt compared with 8.58±0.12 for the dairy control. The difference was related to the characteristic cereal flavour contributed by finger millet, pearl millet, little millet and oats. Fermentation can modify cereal-derived flavour characteristics through the production of organic acids and other metabolites. Similar sensory responses have been reported in cereal-based yoghurt-like products, demonstrating that appropriately formulated millet matrices can achieve favourable sensory acceptance. Vila-Real et al. (2022) likewise reported favourable sensory characteristics for a fermented finger millet-based yoghurt-like beverage.
       
The taste score of the developed yoghurt was 8.22±0.08, whereas the dairy yoghurt recorded 8.64±0.09. Although the conventional yoghurt was preferred, the developed product remained within the highly acceptable range of the hedonic scale. Recent research on millet-containing yoghurt has also demonstrated favourable sensory responses, including improved flavour and sweetness compared with plain yoghurt.
       
Mouthfeel was one of the strongest sensory attributes of the developed product, with a score of 8.34±0.09, compared with 8.71±0.10 for the dairy yoghurt. The high score indicates that the developed product achieved a desirable fermented structure despite the absence of the casein network characteristic of dairy yoghurt. The cereal proteins, starch, dietary fibre and stabilizing system collectively contributed to the cohesive structure of the product.
       
The overall acceptability score was 8.25±0.08 for the functional probiotic millet-based yoghurt compared with 8.64±0.09 for the dairy control. Although the dairy yoghurt was significantly preferred, the difference was only 0.39 point on the 9-point scale. More importantly, the developed millet-based yoghurt scored above 8.0 for every evaluated attribute, demonstrating a high level of overall consumer acceptability.

The study successfully developed a functional probiotic millet-based yoghurt using a composite Nutri-Cereal matrix comprising finger millet, pearl millet, little millet and oats. The developed product exhibited desirable physicochemical properties, appreciable nutritional and mineral composition and considerable dietary fibre content (5.24%). Sensory evaluation confirmed high acceptability, with an overall acceptability score of 8.25±0.08. Although conventional dairy yoghurt received slightly higher sensory scores, the developed product demonstrated promising potential as a nutritious, dairy-free fermented alternative. Thus, composite Nutri-Cereals offer a promising platform for developing value-added functional probiotic yoghurt products.

The authors sincerely acknowledge the College of Food Technology, Vasantrao Naik Marathwada Krishi Vidyapeeth (VNMKV), Parbhani, Maharashtra, India, for providing the necessary laboratory facilities and infrastructure to carry out this research. The authors also express their sincere gratitude to the faculty members and laboratory staff for their valuable guidance, technical assistance and continuous support throughout the course of the study.
 
Disclaimer
 
The views and opinions expressed in this manuscript are those of the authors and do not necessarily reflect the views of the affiliated institution or the publisher.

The authors declare no conflict of interest.