Impact of Tagatose on Physicochemical, Nutritional, and In Vitro Digestive Properties of Toast Bread

It is more attractive to develop effective strategies to reduce sugar intake without compromising food quality with the rising prevalence of obesity and diabetes around the world. Due to its high cost, tagatose has not been widely adopted as a sucrose substitute in toast bread. In the present research, five types of toast containing different proportions (0%, 4%, 8%, 12%, and 16%) of tagatose with sweetness similar to that of sucrose were prepared. The effects of tagatose on microstructural, textural, physicochemical, nutritional, and sensory properties and in vitro digestion were evaluated using techniques such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), rheological test, textural profile assay (TPA), and gas chromatography-mass spectrometry (GC-MS) analysis. The results indicated that after the substitution of tagatose for sucrose, the water-holding capacities of the dough were increased, whereas the specific volume of toast was decreased from 4.74 to 3.01 mL/g (p < 0.05), and the acidity of toast was increased from 1.92 to 2.69°T (p < 0.05). The content of flavor substances, especially alcohols, in the toast was significantly increased by the addition of tagatose. However, the glycemic index (GI) of toast was decreased from 94.39 to 67.96 (p < 0.05). Overall, the addition of 12% or more tagatose will significantly reduce the GI of toasted bread and enrich the flavor, but it will lead to a decrease in specific volume and an increase in acidity. Tagatose is a promising alternative sweetener with low calorie.