This article from Issue 9 of the Analytix Reporter, produced by Merck, examines the use and efficiency of the MQuant® StripScan mobile app to measure the pH of orange juice samples and nitrate concentration of mineral water samples. 

pH and nitrate content are two of the key parameters used to measure the quality and safety of food and beverages (F&B). Generally, pH measurements are carried out using pH strips, pH meters, or electrodes, whereas spectrophotometers or electrodes are used for measuring nitrate content. By using the MQuant® StripScan mobile app the results indicate towards the possible use of it as a viable alternative to more sophisticated and instrument-based methods for pH and nitrate measurements in food and beverage analysis.

Ensuring delivery of quality and safe food and beverage products is critical to the global F&B industry. pH plays an important role in preserving the color, flavor, texture, taste, and nutritional overall value of the product and significantly impacts the quality of final food and beverage product delivered. Moreover, maintaining the proper pH is a food safety issue. For instance, keeping the pH of canned or preserved food at 4.6 helps prevent the growth of toxic bacteria, such as Clostridium botulinum. Additionally, most microorganisms including bacteria, yeasts, and molds cannot survive or grow under very low or high pH values. In the food industry, monitoring the pH of raw materials is essential to prevent their deterioration, which in turn, can affect the shelf-life of the final product. For example, in juices and brews, measuring the pH of water before addition in food processing guarantees a good quality and safe end-product.

A novel method for measuring pH involves the use of the MQuant® StripScan mobile app in combination with test strips. This method provides pH measurements in a few seconds, and also offers additional benefits of automatic data storage, generation of graphs for further documentation, and an automatic data transfer to desktop devices.

Methods and Materials
To measure pH and nitrate in F&B samples, MQuant® test strips (Merck KGaA, Darmstadt, Germany) were used; specifically pH test strips with the range 0-14 and nitrate test strips with the range 0-500 mg/L. The test strips were used according to manufacturer instructions, and readout was performed using the MQuant® StripScan app in conjunction with the appropriate reference cards (Merck).

Results and Discussion
A variety of modern analytical techniques are being used to support the quality control of food and beverages. These include mobile photometry or reflectometry, bench top spectrophotometry, chromatography, mass spectrometry, NMR, X-ray analysis, and atomic spectroscopy. Although these techniques offer high sensitivity and selectivity, most of them also involve laborious chemical work and expensive investment in instruments. Rapid detection techniques based on test strips are gaining popularity. A visual observation of color or fluorescence forms the basis of the test strip detection method. Typically, the test substance reacts with chemicals on the reaction pad(s) of the test strip and results in a color change, which is then compared with a color reference for validation. One drawback of this technique, however, is that a semiquantitative readout is not very accurate, and is prone to individual variations and documentation errors. These aspects are addressed by a new app reader for test strips, the MQuant® StripScan app.

This smartphone-based analytical tool presents a viable alternative to more sophisticated, instrument-based methods, such as pH meters for measuring pH, and spectrophotometers for nitrate measurement.

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*The life science business of Merck operates as MilliporeSigma in the U.S. and Canada.

Published  Aug 31, 2021

Home 9 Food & Beverage 9 Beverage testing with mobile app for pH and nitrate measurements