Description
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.
Chemical Properties
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.
Chemical Properties
white to off-white crystalline powder
Uses
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.
Uses
Sweetener; bulking agent
Definition
ChEBI: Keto-D-tagatose is the straight-chain keto form of D-tagatose. It is an enantiomer of a keto-L-tagatose.
Production Methods
Tagatose is obtained from D-galactose by isomerization under
alkaline conditions in the presence of calcium.
Biotechnological Production
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.
Pharmaceutical Applications
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.
Biological Activity
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.
Side effects
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.
Safety
Tagatose is safe for use in food and beverages. It has been used in
pharmaceutical products.
storage
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.
Purification Methods
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].
Incompatibilities
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.
Regulatory Status
GRAS listed. Included in the FDA Inactive Ingredients Database
(oral and rectal solutions).
