Tagatose Stability in Milk and Diet Lemonade

  The monosaccharide tagatose has been shown to behave physiologically as a prebiotic. To provide its healthful prebiotic effect to consumers, tagatose must not break down during food processing and storage. The objective of this study was to evaluate the storage and thermal stabilities of tagatose in milk and lemonade. Tagatose (0.9% to 1.5%) was added to commercially available shelf stable milk and diet lemonade. Samples were stored at 20, 40, 61, and 81 °C. Tagatose loss was monitored chromatographically. Pseudo‐first‐order rate constants for tagatose degradation were determined along with the reaction's activation energy. No tagatose degradation was observed in lemonade at temperatures equal to or less than 61 °C. Degradation occurred faster in milk because of its higher pH in comparison to lemonade and its dairy proteins enabling the Maillard reaction. The activation energy for tagatose degradation in milk was 24.6 kcal/mol. Using this activation energy, it was estimated that less than 0.1% tagatose would be lost during pasteurization and less than 4% would be lost during storage at 25 °C for 6 mo. Although tagatose degradation occurs in beverages, the extent of its loss during pasteurization and storage would be very low. Tagatose can be formulated into beverages with minimal concern about its degradation and the subsequent loss of prebiotic activity. Practical Application:  Tagatose can be incorporated into beverages as a prebiotic to improve the healthful characteristics of the product without significant degradation.