Validated HPAEC-PAD method for prebiotics determination in synbiotic fermented milks during shelf-life

Interest concerning functional food has been growing in recent years, and much attention has been focused on the choice of prebiotic fibers and probiotic microorganisms added to food products with the aim of improving health, producing synbiotic products. In the work reported here, an innovative analytical method performed by high-performance anion-exchange chromatography (HPAEC) with pulsed electrochemical detection has been optimized and validated for application to the study of prebiotic effects in synbiotic fermented milk prepared by addition of probiotics. The proposed method permits the evaluation of fructooligosaccharides and inulooligosaccharides with degrees of polymerization of 6-7 and 4-7, respectively. Quantitative determination was performed on oligosaccharides, whose standards are not commercially available, by employing calibration curves built by adding a known amount of the fiber used as an ingredient to the matrix. The work provides results from a parallel study on simultaneous variations of prebiotics and probiotics during the shelf life of fermented milk samples. The main advantage over time-consuming, classic enzymatic methods, whose results are limited only to average fiber content, is the possibility of dosing each carbohydrate by performing a single HPAEC run. Validation in terms of detection and quantitation limits, linearity, precision, and recovery was carried out.