Functional Assessment of Tagatose-Rich Syrup in Shortbread Cookie Systems

This study evaluated the performance of a tagatose-rich syrup as an alternative to conventional sweeteners in cookie production, with emphasis on functional properties. The syrup was produced via calcium oxide (CaO)-promoted galactose isomerization, followed by CO2 neutralization, ion-exchange purification, and concentration to 80 °Brix. Its application in making cookies was compared with sucrose and high-fructose corn syrup (HFCS) under equivalent dry solid conditions. Dough made with the tagatose-rich syrup showed numerically higher firmness than HFCS dough, although the difference was not statistically significant, together with similar adhesiveness. In baked cookies, the syrup produced a significantly darker color, with L* values of approximately 54–56 compared to 63–65 for sucrose, and an increase in redness (a*) of nearly 190%. The browning index (BI) followed the same trend, being highest for the syrup (124.4), followed by HFCS (82.5) and sucrose (54.6), consistent with enhanced surface browning. The syrup also reduced spread ratio (∼4.6 vs ∼5.1 for sucrose) and increased thickness, suggesting earlier structure development during baking. Cookies made with the syrup were significantly softer than sucrose-based samples (354.7 g vs 930.8 g hardness) and did not differ significantly in hardness from HFCS (260.6 g). Moisture content was higher in the syrup cookies (4.63%) than in sucrose (3.36%), while water activity did not differ significantly among treatments.