D-tagatose

D-tagatose is a carbohydrate occurring in small amounts in several foods. The solubility in water is approximately 580 g/L at room temperature. As a ketohexose, tagatose reacts in foods in browning reactions like other ketohexoses, for example, fructose.
Tagatose is, depending on the concentration, approximately 92 % as sweet as sucrose and noncariogenic. The caloric value of tagatose is generally set to 1.5 kcal/g.
In the European Union, tagatose is approved as a novel food. In the United States, tagatose has GRAS status and it is also approved in many other countries.

white to off-white crystalline powder

Tagatose is a white, anhydrous crystalline solid. It is a carbohydrate, a ketohexose, an epimer of D-fructose inverted at C-4. It can exist in several tautomeric forms.

D-tagatose is a compound useful in organic synthesis.

D-(-)-Tagatose has been used as a carbohydrates for fermentation. It has also been used as one of the standards to confirm the identity of majority of the metabolites selected by least absolute shrinkage and selection operator (LASSO).

A monosaccharide (hexose) that can be used as a low-calorie sweetener, as an intermediate for synthesis of other optically active compounds, and as an additive in detergent, cosmetic, and pharmaceutical formulation.

ChEBI: Keto-D-tagatose is the straight-chain keto form of D-tagatose. It is an enantiomer of a keto-L-tagatose.

Tagatose is obtained from D-galactose by isomerization under alkaline conditions in the presence of calcium.

Tagatose is produced from galactose, which can be obtained by enzymatic hydrolysis of lactose, the main carbohydrate of milk. Galactose is separated from glucose by chromatography and either isomerized by treatment with calcium hydroxide, subsequent precipitation of calcium carbonate with carbon dioxide, filtration, demineralization with ion exchangers and crystallization [15], or converted enzymatically.
Especially high conversion rates of 96.4 % were obtained with an enzyme extract of an engineered E. coli, and of 60 % at 95 C for A. flavithermus in the presence of borate. Conversion rates of 58 % were reported for an enzyme obtained from a mutant of G. thermodenitrificans [100], of 54 % at 60 C for a recombinant enzyme of Thermus sp. expressed in E. coli, and of more than 50 % at 75 C for E. coli containing an enzyme of A. cellulolytics.
Immobilized enzymes or whole cells were used for practical applications. In some studies, high yields and productivities were achieved.
Immobilized L-arabinose isomerase in calcium alginate produced 145 g/L of tagatose with 48 % conversion of galactose and a productivity of 54 g/Lh in a packed-bed reactor. An enzyme of T. mathranii immobilized in calcium alginate had its optimum at 75 C with a conversion rate of 43.9 % and a productivity up to 10 g/Lh with, however, lower conversion. After incubation of the resulting syrup with S. cerevisiae, purities above 95 % were achieved. The enzyme of T. neapolitana immobilized on chitopearl beds gave a tagatose concentration of 138 g/L at 70 C.
Lactobacillus fermentum immobilized in calcium alginate had a temperature optimum of 65 C. A conversion rate of 60 % and a productivity of 11.1 g/Lh were obtained in a packed-bed reactor after addition of borate.
Direct production of tagatose in yogurt was possible by expressing the enzyme of B. stearothermophilus in Lactobacillus bulgaricus and Streptococcus thermophilus.

Tagatose is used as a sweetening agent in beverages, foods, and pharmaceutical applications. A 10% solution of tagatose is about 92% as sweet as a 10% sucrose solution. It is a low-calorie sugar with approximately 38% of the calories of sucrose per gram. It occurs naturally in low levels in milk products. Like other sugars (fructose, glucose, sucrose), it is also used as a bulk sweetener, humectant, texturizer, and stabilizer, and may be used in dietetic foods with a low glycemic index.

D-Tagatose, a ketohexose acts as a low-calorie functional sweetener. Tagatose can be used as a preservative in cosmetic, detergent and pharmaceutical formulations.Tagatose is also used in diet soft drinks, chewing gum, frozen yogurt and non-fat ice cream.
Potential sugar substitute rarely found in nature. Produced using a biotransformation method with L-arabinose isomerase as the biocatalyst and D-galactose as the substrate.

Some human trials of D-tagatose have found that doses of 30 grams or more cause gastrointestinal side effects like flatulence, diarrhea, nausea, and vomiting.
However, only a minority of people appear to be affected, and mostly only with light to moderate symptom severity.
The GI side effects of D-tagatose seem to be unpleasant but harmless. They’re may be due to osmotic (water-retaining) effects of high D-tagatose doses moving through your intestines.
D-tagatose may interact with some prescription drugs, especially blood sugar lowering drugs, and could cause hypoglycemia (dangerously low blood sugar levels).
And in people with diabetes or a history of kidney stones, temporary rises in uric acid blood levels caused by high dose D-tagatose may be an issue.

Tagatose is safe for use in food and beverages. It has been used in pharmaceutical products.

Tagatose is stable under pH conditions typically encountered in foods (pH>3). It is a reducing sugar and undergoes the Maillard reaction.
Tagatose is stable under typical storage conditions. It caramelizes at elevated temperature.

Crystallise D(-)-tagatose from EtOH/H2O (6:1). It mutarotates from [] 22D +2o (2minutes) to –5.0o (30minutes) (c 4, H2O). The phenylosazone crystallises from aqueous EtOH with m 185-187o(dec), and [] 23D +47o (c 0.82, 2-methoxyethanol). [Totton & Lardy J Am Chem Soc 71 3076 1949, Gorin et al. Canad J Chem 33 1116 1955, Reichestein & Bossard Helv Chem Acta 17 753 1934, Wolfrom & Bennett J Org Chem 30 1284 1965, Beilstein 1 IV 4414.] In D2O at 27o 1H NMR showed the following ratios: -pyranose (79), -pyranose (16), -furanose (1) and -furanose (4) [Angyal Adv Carbohydr Chem 42 15 1984, Angyal & Pickles Aust J Chem 25 1711 1972].

A Maillard-type condensation reaction is likely to occur between tagatose and compounds with a primary amine group to form brown or yellow-brown colored Amidori compounds. Reducing sugars will also interact with secondary amines to form an imine, but without any accompanying yellow-brown discoloration.

GRAS listed. Included in the FDA Inactive Ingredients Database (oral and rectal solutions).