Portable fibre-optic device for measuring the total and volatile acidity of beverages and liquid foods

The technology of this invention is based on a membrane that changes its colour and fluorescence as a function of the total acid concentration in a liquid sample. This technology allows the determination of total acidity (TA) and volatile acidity (VA) in situ, and in a simple, fast, clean, cheap and accurate way in vinegar, wine and any other type of liquid sample, where the pH differences between the most acidic and the least acidic sample can differ by only 0.1 pH units.

To carry out the measurement, the membrane (a 0.9 mm diameter disc: Paper-FM) is inserted directly into the sample for 15 seconds, and then inserted into the portable measuring device to obtain a direct value of the TA or VA in g/L, without the need for any additional reagent, as shown in the attached picture.

The technology of this invention has been validated on wine and vinegar samples of different origin.

The validation has been carried out by comparing the results obtained with the technology of the invention and with official reference methods:

Enzymatic method (Enz) to determine the concentration of acetic acid in wine (volatile acidity), and volumetric methods: OIV-AS-313-02-ACIVOL method for volatile acidity (VolV.) and OIV-AS-313-01-ACITOT method for total acidity (VolT.).

Advantages and benefits

• Determination of TA and VA in a simple way. No specific qualification is required to use the technology, as the determination of TA and VA is based solely on introducing the membrane directly into the sample for 15 seconds.

• Fast determination of TA and VA (15 seconds), saving time and lowering the cost of analysis. Current market methods (volumetric and enzymatic) require times ranging from 10 min to 20 min.

• Environmentally friendly technology, as it does not require additional reagents, unlike volumetric methods that require additional reagents and generate toxic waste, and enzymatic methods that use expensive and unstable (rapidly deteriorating) reagents (enzymes).

• The membrane (device consumable) is reversible, can be stored at room temperature for months, is reusable and extremely stable. A single 0.9 mm diameter membrane can be used for more than 30 measurements, which in turn means reduced costs.

• The device is small, portable and robust, allowing on-site determinations. This avoids the maintenance and set-up of equipment, and the collection, transport and storage of samples, which translates into a reduction in analysis time and costs.