Basic Guidelines for Beverages How to Ensure Taste and Safety of Non-Alcoholic Beverages and Softdrinks
In this article we describe some essential analytical parameters and general lab tasks applied to analyze the aforementioned products. Some facts and explanations about the parameters, as well as some guidance on how to perform these tasks best, are presented.
Today, the sheer number of specialized waters, juices and soft/functional drinks available worldwide is staggering. Quality and production control tests such as pH and conductivity, hardness, alkalinity, Brix, acidity, sodium and chloride content are paramount to the palatability, consistency and shelf-life of these alcohol-free products. There are some guidelines that showcase selected analyses applied to non-alcoholic beverages to help ensure consistent quality.
Monitoring pH Value
The pH value indicates how much and how strong acids or leaches present in the sample are. Sample solutions with a pH below 7 are acidic. If the pH is above 7, the solution is basic (also called alkaline). At pH 7.0 the solution is neutral. By definition, the pH value is related to the concentration of the hydronium ion H3O+ which is formed when an acid such as citric, lactic or acetic is dissolved in water. In beverages, the pH value is related to the sourness, and can thus, be a limiting quality parameter.
The determination of the pH value requires a meter and a suitable electrode. Manufacturers usually offer a selection of models to cover the actual customer needs. Small meters for simple routine tasks or elaborate models with color display, touchscreen, high resolution, data storage and many more features are available. The user can also choose from a variety of electrodes. Shape of the glass membrane (round, flat, puncture, etc.,) and shaft material (glass, PEEK, polysulfone) are just two decisive factors. In most beverage samples standard pH electrodes can be easily applied.
No interference is expected from the sample matrix, such as proteins clogging the electrode’s junction or fats covering the measuring glass membrane. Because of the importance of the pH value, it is recommended to apply a two or three point calibration.
How to Calibrate pH–Measurement
For water where pH is usually around 7, three calibration points at pH 4, 7 and 9 (or 10) are good practice. It ensures that pH values below and above 7 are measured correctly. If the samples are acidic, also a two point calibration between 4 and 7 is acceptable and yields reliable results.
Nowadays, pH buffers need to be traceable to generally accepted reference standards (e.g., NIST). Also, it is advisable to respect the expiry date of the buffers to ensure reliable calibrations. Furthermore, it is recommended to use ready-to-use buffers in order to avoid any errors due to dilution or impurities. Discard used buffers. Backfilling them may contaminate the remaining buffer solution.
What Conductivity Tells Baout A Beverage
Electrical conductivity is a non-specific sum parameter over all dissolved ionic species such as salts, acids and bases. This means that this technique is not able to differentiate between diverse kinds of ions.