Development of a high protein and fiber beverage based on amaranth, rice bran and whey using solid-state and submerged fermentation

The growing demand for nutritious beverages creates opportunities for developing fermented dairy products rich in probiotics, prebiotics, and bioactive compounds. This study evaluated how solid-state fermentation (SSF) and submerged fermentation (SmF) influence the sensory, physicochemical, and microbiological properties of a beverage formulated from amaranth flour, rice bran, and whey. SSF was carried out with Aspergillus oryzae, followed by SmF using Lacticaseibacillus paracasei and Lactobacillus delbrueckii. Maximum SSF colonization was achieved with A. oryzae (miso kōji) on 50%-50% or 80%-20% amaranth-rice bran mixtures (T4, T8) at ~48 h. Beverage T4 demonstrated superior organoleptic qualities, with lower acidity, enhanced aroma and colour (p < 0.05), favourable taste, and acceptability. Microbiologically safe, T4’s estimated shelf life was 29 d at 4°C. Proximate analysis showed 7.72% protein and 18.13% fiber (values notably higher than comparable beverages), with increased carbohydrate availability, aligning with current trends in high-nutrition functional beverages.