Drinking yoghurt has long been a staple of the fermented dairy aisle, prized for its convenience, its live bacterial cultures, and its broad appeal across cultures and age groups. Now, a team of food scientists in Bangladesh has taken this humble beverage in a bolder direction, fortifying it with beetroot pulp and orange juice to create a functional drink that packs a measurable antioxidant punch. The study, published in Food Science & Nutrition, systematically compared three formulations of beetroot-and-orange-enriched drinking yoghurt, evaluating everything from protein content and carotenoid levels to taste scores and microbial safety over a 35-day refrigerated shelf life. The results offer a compelling glimpse into how everyday dairy products might be re-engineered to deliver more health-promoting compounds without sacrificing the qualities that make yoghurt beloved in the first place.

The rationale behind the study rests on the well-documented bioactive profiles of its two plant ingredients. Beetroot, a root vegetable of the Chenopodiaceae family, ranks among the top ten antioxidant vegetables thanks to its rich stores of betalains, phenolic acids, saponins, catechins, and flavonoids. It is also unusually high in dietary nitrates, which the human body converts into nitric oxide, a molecule that improves blood flow and cardiovascular function, a property that has earned beetroot a place in athletes’ performance regimens. Orange juice, meanwhile, contributes more than 100 tentatively identified carotenoids across citrus fruits, alongside generous vitamin C, flavonoids, and limonoids with anti-inflammatory and immune-supporting properties. Combining the two in a fermented dairy matrix, the researchers reasoned, could yield a beverage whose bioactive content far exceeds that of plain yoghurt, while the dairy proteins themselves may act as natural carriers that enhance the bioavailability of plant polyphenols through hydrophobic and electrostatic binding.

The experimental design was straightforward but rigorous in its analytical detail. Fresh beetroot roots and sweet oranges at commercial maturity were purchased from a certified market in Dhaka and transported under refrigeration. The beetroot was peeled, cubed, and blanched in boiling water for two minutes to inactivate the enzymes peroxidase and polyphenol oxidase, a step that stabilizes color and carotenoids, before being homogenized into a smooth pulp. Orange juice was extracted mechanically, filtered through muslin cloth, and stored in amber bottles at 4°C to prevent light-induced degradation of vitamin C and carotenoids. Full-fat cow’s milk was heat-treated at 85°C to 95°C for five minutes to denature whey proteins and improve water-holding capacity, then cooled and inoculated with a commercial starter culture of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, fermented to pH 4.5, and blended with the plant ingredients.

Three formulations were prepared, each containing a constant 30 milliliters of orange juice but varying amounts of beetroot pulp. Sample A combined 240 grams of yoghurt with 30 grams of beetroot pulp, Sample B paired 225 grams of yoghurt with a hefty 45 grams of pulp, and Sample C mixed 255 grams of yoghurt with just 15 grams. After homogenization, the drinks were bottled in sterilized 250-milliliter glass containers and refrigerated. This gradient approach allowed the team to probe how increasing beetroot concentration would shift the balance between nutritional enhancement, antioxidant capacity, and the sensory qualities that ultimately determine whether consumers will actually buy such a product.

The proximate analysis revealed meaningful differences tied directly to formulation. Moisture ranged from 81.72 percent in Sample C to 84.27 percent in Sample B, while Sample C, with its higher proportion of yoghurt, delivered the most nutrient-dense profile: 3.75 percent protein, 3.67 percent fat, and 10.33 percent carbohydrate. Sample B, diluted by its large beetroot fraction, had the lowest protein at 3.07 percent and fat at 3.15 percent. The pattern makes intuitive sense, since yoghurt contributes milk solids, proteins, and minerals, whereas beetroot pulp adds water, fiber, and plant solids that shift the moisture-to-total-solids ratio. These water-binding interactions among milk proteins, plant fibers, and polysaccharides matter greatly in fermented dairy, influencing both consistency and stability over time.

The bioactive results told an equally clear story. Sample B, with the most beetroot, achieved the highest DPPH radical-scavenging activity at 56.1 percent inhibition, the strongest total phenolic content at 51.4 milligrams of gallic acid equivalents per 100 grams, and the highest flavonoid content at 14 milligrams of catechin equivalents per 100 grams. Its IC50 value of 429.4 parts per million was the lowest, meaning less extract was needed to neutralize half of the free radicals in the assay. Sample C, with the least beetroot, lagged behind on every bioactive measure, failing to reach 50 percent inhibition even at the highest concentration tested. Beta-carotene-equivalent carotenoid content varied only narrowly, from 4.5 to 4.9 milligrams per 100 grams, across all three drinks. The researchers validated their spectrophotometric carotenoid method carefully, achieving 96.4 percent recovery, a calibration linearity above 0.99, and intra-day and inter-day precision below 5 percent relative standard deviation, though they caution that betalains and citrus pigments may overlap spectrally and recommend chromatographic confirmation in future work.

Sensory evaluation, conducted with a 30-member consumer panel using a nine-point hedonic scale, revealed the study’s central tension: more beetroot means more antioxidants, but also less palatability. Sample A, the moderate formulation, won decisively, scoring 7.63 for appearance, 8.00 for aroma, 8.07 for taste, and 7.90 for texture, all statistically superior to the other two formulations at p < 0.001. Sample C scored lowest on every attribute, a somewhat puzzling result given its lowest beetroot content, though the authors note that overall formulation balance and interactions among ingredients, rather than beetroot intensity alone, likely shaped the panel’s verdicts. The citrus component may play a helpful role here, since the natural sugars, acids, and volatile aromatics of orange juice can mask the earthy geosmin-derived notes that make beetroot polarizing at high concentrations.

On the safety and stability front, the news was reassuring. The pH of all three formulations declined gradually over 35 days of refrigerated storage, from around 4.5 initially to as low as 4.0 in Sample C by day 35, a normal post-acidification pattern driven by the residual metabolic activity of lactic acid bacteria. More importantly, coliform bacteria and Escherichia coli were never detected in any sample at any time point, with counts remaining below the detection limit of one colony-forming unit per milliliter throughout the entire storage period. That performance comfortably meets regulatory limits set by agencies such as the FDA and EFSA, which cap coliforms and E. coli in refrigerated foods at fewer than 10 colony-forming units per gram, and it points to good hygienic processing, proper fermentation control, and effective cold-chain preservation.

The authors are candid about the limitations that temper these findings. The study relied on a single production run, lacked an unfortified control, and measured only selected microbial indicators, leaving total viable counts and starter-culture dynamics uncharacterized. Nutritional analysis stopped at macronutrients, without profiling vitamins, minerals, or specific phytochemicals. Because technical replicates rather than independent batches formed the basis of the physicochemical data, the results should be read as preliminary formulation-level observations rather than definitive product claims. Still, the practical takeaway is clear and actionable: a moderate beetroot-and-orange fortification, as in Sample A, best preserves the taste and texture consumers expect, while a heavier beetroot load, as in Sample B, maximizes antioxidant and phenolic content. Future work with replicated production trials, chromatographic carotenoid profiling, and larger consumer panels will determine whether these vibrant pink-and-orange functional drinks can graduate from the laboratory bench to the supermarket chiller, but the evidence so far suggests that the humble drinking yoghurt has considerable untapped potential as a delivery vehicle for plant-derived bioactive compounds.

Subject of Research: Functional drinking yoghurt fortified with beetroot pulp and orange juice

Article Title: Physicochemical, Bioactive, Sensory, and Microbial Evaluation of Functional Drinking Yoghurt Fortified With Beetroot and Orange Juice

Article References: Khan, M. M. I., Ali, M. N., Tabassum, A., Bhattacharjee, D., Alam, S., & Islam, M. S. (2026). Physicochemical, Bioactive, Sensory, and Microbial Evaluation of Functional Drinking Yoghurt Fortified With Beetroot and Orange Juice. Food Science &amp; Nutrition, 14(10), Article e72452. https://doi.org/10.1002/fsn3.72452

Image Credits: AI Generated

DOI: 10.1002/fsn3.72452

Keywords: drinking yoghurt, beetroot, orange juice, functional foods, antioxidants, betalains, carotenoids, DPPH, total phenolic content, probiotics, food safety, sensory evaluation