Validation of Enzytec™ Liquid D-Glucose for Enzymatic Determination of D-Glucose in Selected Foods and Beverages: Official Method 2024.03 First Action.

Background: Glucose is the most abundant monosaccharide. Glucose is mainly made by plants during photosynthesis from water and carbon dioxide, using energy from sunlight. It is therefore contained in many foodstuffs naturally or added later as an ingredient.

Objective: To validate the performance of the Enzytec™ Liquid D-Glucose for the determination of D-glucose in food and beverages such as fruit and vegetable juices, soft drinks, wines, and beer.

Methods: The kit contains two ready-to-use components, which makes handling easy and suitable for automation. D-Glucose is phosphorylated to glucose-6-phosphate (G-6-P) by a hexokinase and ATP. In the presence of glucose-6-phosphate dehydrogenase and NAD, G-6-P reacts to gluconate-6-phosphate, whereby NADH is formed and measured at a wavelength of 340 nm within 20 minutes.

Results: Mannose and D-fructose interfere at 5.1 and 12.5 g/L (or more), respectively. Sulfite does not interfere up to 1.25 g/L. The calculated LOD and LOQ when using a test solution volume of 100 µL are 1.4 and 4 mg/L, respectively. The linear measurement range is from 4 to 2000 mg/L D-glucose. Trueness was checked by using materials from NIST (cranberry juice) and one reference wine from the German Wine Analysts. Spiking of wine, beer, and juices resulted in recoveries between 93 and 101%. Analysis of NIST SRM 3282 resulted in an intermediate precision of 4.1%. For automation, three applications with different test solution volumes and different but overlapping measurement ranges were validated. Linearity is given from 2.4 up to 10 000 mg/L.

Conclusions: The method is robust and accurate for manual and automated applications. The method was approved as AOAC Official Method of Analysis℠.

Highlights: The ready-to-use components of the test kit have a shelf life of at least 29 months from the date of manufacture.