Storage stability of tagatose in buffer solutions of various compositions

Tagatose is a minimally absorbed monosaccharide that has prebiotic properties. For this prebiotic effect to be achieved, tagatose should remain stable and not degrade during food processing and storage. This study evaluated the storage stability of tagatose in solutions as affected by buffer type, buffer concentration, pH, and temperature. Tagatose does degrade during storage. Minimal tagatose loss and browning were observed in 0.02 M phosphate and citrate buffers at pH 3. In 0.1 M buffers at pH 3 and 40 °C, approximately 5% tagatose was lost over 6 months and slight browning occurred. Tagatose degradation was enhanced at pH 7, especially in phosphate buffer, where it occurred faster than in citrate buffer. Higher buffer concentrations also enhanced tagatose loss. In phosphate buffers at pH 7, browning accompanied the tagatose degradation, increasing to a maximum and then decreasing. To deliver the prebiotic effect from tagatose, shelf-stable beverages should be formulated to the lowest buffer concentration and pH possible to optimize tagatose’s stability.