Low-temperature sweetening

Barichello, V., Yada, R. Y, Coffin, R. H., Stanley, D. W. (1990). Low temperature sweetening in susceptible and resistant potatoes Starch structure and composition. J. FoodScL, 54, 1054-1059. 

Pinhero, R. G., Copp, L. J., Amaya, C. -L., Marangoni, A. G., Yada, R. Y. (2007). Roles of Alcohol dehydrogenase. Lactate dehydrogenase and Pyruvate decarboxylase in Low Temperature Sweetening in a tolerant and susceptible varieties of Potato (Solanum tuberosum). Physiologia Plant, 130(2), 230-239. 

Fmctose is sweeter than sucrose at low temperatures (- S C) at higher temperatures, the reverse is tme. At 40°C, they have equal sweetness, the result of a temperature-induced shift in the percentages of a- and P-fmctose anomers. The taste of sucrose is synergistic with high intensity sweeteners (eg, sucralose and aspartame) and can be enhanced or prolonged by substances like glycerol monostearate, lecithin, and maltol (19). 

The sweetness of fmctose is 1.3—1.8 times that of sucrose (10). This property makes fmctose attractive as an alternative for sucrose and other commercially available sweeteners. Fmctose is probably sweetest ia comparison with sucrose when cold and freshly made up ia low concentrations at a slightly acidic pH (5). This relative sweetness difference is commonly attributed to changes ia fmctose stmcture when cold ( P-D-fmctopyranose(l), sweet) as compared to the stmcture when the sweetener is warm ( P-D-fmctofuranose (2), less sweet). Based on nmr spectroscopy and sensory panel evaluation of sweetness, however, it has been observed that the absolute sweetness of fmctose is the same at 5°C as at 50°C, and is not dependent on anomeric distribution (11). Rather, it maybe the sweetness of sucrose, which changes with temperature, that gives fmctose sweetness the appearance of becoming sweeter at low temperatures. 

In the low temperature process, the slurry is heated to 105—108°C and held at temperature for 5—10 minutes. The resulting 1—2 DE hydrolyzate is flashed to atmospheric pressure and held at 95—100°C for one to two hours in a batch or continuous reactor. Because the enzyme is not significantly deactivated at the first-stage temperature, a second enzyme addition is not needed. This process is used woddwide throughout the starch-based sweetener industry and has been judged the most efficient process for dextrose production. 

The inherent technical problems of making high boilings from isomalt are considerable but they have been solved. Isomalt has only 45-60% of the sweetness of sugar, and therefore the reduced sweetness is normally made up by adding an intense sweetener. Also, the solubility of isomalt at 20 °C is only 24.5 g per 100 g water thus at low temperatures isomalt... 

Another example of a protease-catalyzed commercial process, which in this case uses the enzyme in a synthetic mode, is the completely regio- and stereoselective production of the low-caloric sweetener aspartame developed by DSM-TOSOH [15] (Fig. 7.9). Aspartame is a dipeptide consisting of the amino acids phenylalanine and aspartic acid, which are coupled by the enzyme thermolysin from Bacillus thermoproteolyticus. For an efficient coupling, relatively high temperatures are required and the amount of water in the system must be kept low to drive the reaction in the desired direction. Thermolysin, which is a metallo-endoprotease, meets these two requirements. It is thermostable, and it works in an organic solvent, which is required to keep the water activity low. In practice, however, organic solvents were not necessary, since the product aspartame forms an insoluble complex with unreacted D-Phe-OMe, which crystallizes out of the aqueous medium. 

Enzymes are characterized by unusual specific activities and remarkably high selectivities. They are effective catalysts at relatively low temperatures and ambient pressure. The primary driving force for efforts to develop immobilized forms of these biocatalysts is cost, especially when one is comparing process alternatives involving either conventional inorganic catalysts or soluble enzymes. Immobilization can permit conversion of labile enzymes into forms appropriate for use as catalysts in industrial processes—production of sweeteners, pharmaceutical intermediates, and fine chemicals—or as biosensors in analytical applications. Because of their high specificities, immobilized versions of enzymes are potentially useful in situations where it is necessary to obtain high yields of the desired product... 

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