Formulation of Clear Prebiotic Drinking Water

🧪 Today's Task

Client: Clear prebiotic drinking water
Our role: Formulation and clarity optimisation

Task: Develop and optimise a clear prebiotic drinking water by selecting a soluble prebiotic fibre, optimising clarity and mineral compatibility, and standardising the formulation.

📍 Lab location: Food Research Lab

Event: Formulation of Clear Prebiotic Drinking Water

The aim was a functional drink that looks and tastes like plain water: a fully dissolved prebiotic fibre, added minerals, no haze and no sediment. We screened soluble fibres, worked out the order of addition, pH and filtration conditions, and compared two prototype variants for dissolution time, turbidity, light transmittance, pH and soluble solids before choosing one for pilot-scale work.

This diary covers the formulation stage of an unflavoured, water-like product. For a flavoured, carbonated prebiotic drink built on root and botanical extracts, see our prebiotic drink formulation diary; for a 90-day storage study of a functional prebiotic beverage, see quality validation and shelf-life evaluation of a prebiotic beverage.

😊 How I Felt Before Starting

A clear drink leaves nowhere to hide. Any undissolved fibre, any reaction between the fibre and the added minerals, shows up straight away as haze or a fine sediment at the bottom of the bottle.

The challenge I expected was getting enough prebiotic fibre into the water to be meaningful without losing transparency, stability or a neutral taste, while keeping the dissolved minerals compatible with it. I went in planning to control the variables that usually cause haze: the fibre chosen, how long it hydrates, the order in which ingredients go in, pH and filtration.

🧪 What We Did Today?

Product Formulation Plan

The target was a transparent, water-like functional beverage with complete prebiotic dissolution, good ingredient compatibility and a neutral sensory profile. The work covered:

1. Selection of a suitable prebiotic fibre
2. Ingredient compatibility and formulation optimisation
3. Clarity and pH optimisation
4. Formulation standardisation

Key Steps Followed Today

1. Prebiotic selection and ingredient screening

We screened different prebiotic fibres for solubility, molecular weight, clarity and effect on taste. The selected fibre dissolved quickly, gave good clarity and had minimal taste impact, and the team checked it against the FSSAI requirements relevant to the product.

2. Formulation optimisation

The prebiotic was dispersed in purified water and allowed to hydrate fully before the minerals were added. pH was then adjusted to improve ingredient compatibility and limit haze formation.

Prototype variants

Two variants were prepared. Variant 1 was the first optimised combination of fibre concentration, mineral composition and processing conditions. Variant 2 refined the fibre selection, ingredient addition sequence, pH adjustment and filtration parameters to improve clarity and dissolution. Both were tested under identical analytical conditions.

3. Clarity and compatibility evaluation

Both variants were measured for dissolution time, turbidity (NTU), light transmittance (%), pH, total soluble solids (°Brix) and filtration efficiency, and checked visually for haze and precipitation.

4. Formulation standardisation

After the comparison, the selected formulation was standardised by fixing ingredient ratios, order of addition, mixing conditions, hydration time and filtration parameters, so that each batch comes out the same.

📚 What I Learned?

Observations & Learnings

• Fibre choice decides clarity. A highly soluble fibre was essential for a clear drink with no haze or sediment. This matches the published behaviour of fructans: short-chain oligofructose is highly soluble, while longer-chain inulin is much less so^[2].
• Order of addition matters. Letting the fibre hydrate fully before adding the minerals, and controlling mixing, gave complete dissolution and a uniform drink.
• pH and mineral compatibility go together. Adjusting pH reduced interactions between the minerals and the fibre that otherwise showed up as slight haze.
• Neutral ingredients keep it looking like water. Ingredients with no taste or colour of their own helped keep the water-like appearance and flavour.
• Clarity has to be measured, not judged by eye. Turbidity and light transmittance separated two variants that both looked clear on the bench.

Outcome (Analysis Table)

Table 1. Clarity and compatibility results for the two variants

Interpretation

Both prototypes dispersed well and looked clear. Variant 1 performed acceptably, dissolving in 4.2 minutes with 96.8% light transmittance and 1.3 NTU turbidity, but showed slight haze from minor interactions between the minerals and the prebiotic. Variant 2 was better on every clarity measure: it dissolved faster (2.8 minutes), transmitted more light (99.2%), had lower turbidity (0.7 NTU) and filtered at 99.4% efficiency with no visible haze or precipitate. pH and soluble solids were almost identical, which suggests the gain came from the refined fibre selection, addition sequence and pH adjustment rather than from a change in total solids.

For context, India’s drinking water standard, IS 10500:2012, sets an acceptable turbidity limit of 1 NTU^[3]. That standard covers drinking water rather than formulated beverages, but it is a useful yardstick for a product sold as “water”: Variant 2 sits below it and Variant 1 just above.

On this evidence, Variant 2 was selected as the optimised formulation for pilot-scale development.

✅ What Went Well?

• Two working prototypes of a clear prebiotic drinking water, both with good dispersion and visual clarity.
• Variant 2 cut dissolution time from 4.2 to 2.8 minutes and turbidity from 1.3 to 0.7 NTU, and raised light transmittance from 96.8% to 99.2%.
• The haze in Variant 1 was traced to mineral–prebiotic interaction and removed in Variant 2 by refining the addition sequence and pH adjustment.
• A standardised process: ingredient ratios, order of addition, mixing, hydration time and filtration are now fixed for pilot-scale batches.

⚠️ What Could I Have Done Better?

• Evaluate alternative low-molecular-weight prebiotic fibres for faster processing.
• Test different hydration times to map their effect on dissolution.
• Optimise mixing speed and shear during ingredient addition.
• Compare filtration performance across membrane pore sizes, and record filtration efficiency for every variant.
• Check robustness across source waters with different mineral profiles.
• Run replicate batches and report means with variation, so small differences such as 0.1 pH units can be judged.

For brands & formulators

Planning a functional water or a clear fibre-enriched drink? The difficult part is usually not adding the fibre but keeping the drink clear, stable and neutral-tasting once minerals, acids and processing are involved. FRL’s beverage team screens fibres for solubility, sets the order of addition and pH, and measures clarity with turbidity and light transmittance before scale-up.

Two points to settle early. Whether a product can be called “prebiotic” depends on the fibre and the dose a serving delivers, and the scientific definition requires a demonstrated health benefit^[1]. And the product’s regulatory category in India needs checking against the FSSAI standards for non-alcoholic beverages. For more on adding functional ingredients to drinks, see our guide to bioactive ingredients in functional beverages, and for another beverage bench trial, our lemon lime sparkling water diary.

Talk to our beverage research team about your functional water or clear beverage.

1. Gibson, G. R., Hutkins, R., Sanders, M. E., Prescott, S. L., Reimer, R. A., Salminen, S. J., Scott, K., Stanton, C., Swanson, K. S., Cani, P. D., Verbeke, K., & Reid, G. (2017). Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nature Reviews Gastroenterology & Hepatology, 14(8), 491–502. https://doi.org/10.1038/nrgastro.2017.75 (cited for the definition of a prebiotic).
2. Franck, A. (2002). Technological functionality of inulin and oligofructose. British Journal of Nutrition, 87(S2), S287–S291. https://doi.org/10.1079/BJN/2002550 (cited for oligofructose being highly soluble and inulin much less soluble).
3. Bureau of Indian Standards. (2012). IS 10500:2012 Drinking water: Specification (second revision). BIS. https://consumerhelpline.gov.in/public/assets/docs/bis/IS10500-2012.pdf (cited for the 1 NTU acceptable and 5 NTU permissible turbidity limits, Table 2).