Short communication: Determination of inulin in milk using high-performance liquid chromatography with evaporative light scattering detection

The objective of this study was to develop an HPLC method for the determination of inulin in a dairy matrix. Inulin is often added to dairy products to act as a source of dietary fiber as well as to provide technological functionality (e.g., water-holding or fat-replacing functions). The method includes hydrolysis of inulin with inulinase enzyme and determination of released fructose and glucose by HPLC coupled with evaporative light scattering detection, using water as the mobile phase. The effect of the milk background was investigated, preparing standards in milk, whey, or permeate and subjecting them to inulinase treatment. The developed method showed satisfactory linearity (R2 = 0.98 for glucose and 0.99 for fructose), good repeatability (relative standard deviation, RSD, ranging from 2.2 to 7.3% for glucose and from 0.6 to 2.3% for fructose), satisfactory reproducibility (RSD from 8.1 to 12.9% for glucose and from 3.1 to 4.9% for fructose), and good recovery (98.4 to 103.6%).