Sugar – starch – and carbohydrates – Processes – Carbohydrate manufacture and refining
Patent
1994-01-06
1996-02-27
Lieberman, Paul
Sugar, starch, and carbohydrates
Processes
Carbohydrate manufacture and refining
127 30, 127 31, 514 53, 514777, 536 111, 536127, C13F 3200, C13K 500, A61K 31715, C07H 100
Patent
active
054945259
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a novel crystalline anhydrous lactitol and a process for the preparation thereof by crystallization from an aqueous solution, and the use thereof.
Lactitol is a special sweetener replacing saccharose; however, its energy content is only half of that of saccharose, and it does not cause an elevated blood glucose content; furthermore, it is friendly to the teeth (cf. Developments in Sweeteners, Ed. Grenby, T. H., Vol. 3, 1987, pp. 65-81).
The preparation of lactitol from lactose has long been known. Industrially lactitol is prepared analogously with the preparation of sorbitol, by hydrogenation in the presence of a Raney nickel catalyst. An aqueous solution of lactose, typically having a concentration of 30% to 40% by weight on account of the low solubility of lactose, is hydrogenated at 70.degree. C. to 130.degree. C. at a pressure of 30 atm to 74 arm. The preparation has been described by Wolfrom, M. L., Burke, W. J., Brown, K. R. and Rose, R. S., J. Am. Chem. Soc. 60 (1938), pp. 571-573.
Crystalline lactitol has been reported to occur in anhydrous form (anhydride) as well as in the form of monohydrate, dihydrate and trihydrate, which have all been known for a long time with the exception of pure monohydrate and Trihydrate. Among the crystal forms of lactitol, lactitol monohydrate is of great commercial interest e.g. on account of its low hygroscopicity.
In accordance with the above-stated reference (Wolfrom et al., 1938), "lactitol anhydride" could be crystallized by adding ethanol to a lactitol solution evaporated to a high concentration. After a crystallization time of one month (from anhydrous ethanol), the lactitol yield was 80%; the product was recrystallized from a water-ethanol solution in an ice bath. The resultant "lactitol anhydride" was a highly hygroscopic substance. The crystal form was tetraedric, the melting point was 144.degree. C. to 146.degree. C. and the specific rotation in water +14.degree. (4 g/100 ml, 23.degree. C.).
In J. Am. Chem. Soc. 74 (1952), p. 1105, Wolfrom et al. state the above "lactitol anhydride" to be metastable, since in renewed tests carried out at two different laboratories only dihydrate was crystallized, having a melting point of 72.5.degree. C. to 74.degree. C. On the basis of the studies presently conducted, the product disclosed by Wolfrom et al. (1938) was an impure dihydrate and not crystalline anhydrous lactitol. The dihydrate prepared by Wolfrom et al. was found to have been anhydrated in the melting point determination, as has been shown in the reference example set out hereinbelow. Therein dihydrate turns into a powdery anhydride below 70.degree. C. when the melting point measurement is started at room temperature, and then melts at about 146.degree. C.
Lactitol hydrate powders anhydrated to a water content below 3% have been prepared by drying both a lactitol solution and crystalline hydrate. The hygroscopicity of these powders is made use of in the drying of moist mixtures (European Patent Application No. 0231643, 1986).
Japanese Patent Application No. 64-19452 (1989) discloses "lactitol anhydride" which is prepared by drying crystalline lactitol monohydrate. The product is hygroscopic and has a melting point of 121.degree. C. to 123.degree. C.
The crystalline anhydrous lactitol of the invention is prepared by crystallizing from an aqueous solution having a lactitol content of more than 70%, preferably more than 90%, on dry solids and having a dry solids content of 80% to 95% by weight, preferably about 90% by weight, in the temperature range 70.degree.-100.degree. C. The crystallization is advantageously carried out by first evaporating, optionally seeding, followed by cooling from about 95.degree. C. to about 80.degree. C., whereafter the crystals are separated from the mother liquor and washed and dried, if necessary.
According to another preferred method, the lactitol solution is evaporated under stirring at a temperature of 80.degree. C. to 90.degree. C., seed crystals are added if desired, and the evaporation is con
REFERENCES:
patent: 3973050 (1976-08-01), Hayashibara et al.
patent: 4216025 (1980-08-01), Monti
patent: 5160546 (1992-11-01), Kawashima et al.
patent: 5162517 (1992-11-01), Darsow
STN International File CA, Chemical Abstracts, vol. 114, No. 7, 18 Feb. 1991 (Columbus, Ohio, US), Kawashima Shigeru, et al: "Manufacture of lactitol anhydrate crystals and crystal compositions containing lactitol anhydrate", abstract no. 60708u, & JP 02255694 A2 16 Oct. 1990, JP 89-75204 29 Mar. 1989.
Trans. Faraday Soc., vol. 24, 1928 M. L. Wolfrom et al.: "Crystalline lactositol", see p. 571-p. 573 Mar. 1938.
STN International, file CA, Chemical Abstracts vol. 114, No. 5, 4 Feb. 1991, (Columbus, Ohio, US) Kawashima Shigeru et al: "Novel lactitol anhydrate crystals, raw sugars crystals containing them, and their manufacture", abstract No. 41308x, & JP 02200695 A2 8 Aug. 1990, JP 89-19452 31 Jan. 1989.
Heikkila Heikki O.
Nurmi Juha V.
Pepper Tammy
Hailey Patricia L.
Lieberman Paul
Xyrofin Oy
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