The existing patented technologies of the production of lactulose were analyzed, and leading producers were defined. Crystalline lactulose was produced via the spray drying of lactulose solutions with various mass fractions of solids. The principal dependences of the finished product output on the drying temperature, the solution flow rate, the air flow rate generated by an aspirator, and the gas spray rate were studied. The results of analyzing the presented dependences allowed us to determine the optimal mass fraction of solids in a solution for spray drying. The results of studying the quantitative parameters of dry lactulose, including hygroscopicity, particle size, moisture content, and finished product solubility index, were presented
lactulose, lactose, drying, solution, temperature, solution flow rate, air flow rate, mass fraction, solubility index
Lactulose is a carbohydrate that belongs to the class of oligosaccharides and the subclass of disaccharides. Its molecule consists of the galactose and fructose moieties. Lactulose is obtained from milk sugar (lactose) via the deep processing of milk. Lactulose is a white odorless sweet crystalline substance, which is well soluble in water .
Lactulose is a carbohydrate, which is indigestible in the gastrointestinal tract, but usable by beneficial microflora as a nutritious substrate .
The bifidogenic properties of lactulose were first revealed and studied by F. Petuely, a British pediatrician, who has succeeded in separating lactulose from human breast milk and also in establishing its beneficial effect on the destroyed microbiocenosis of the gastrointestinal tract of artificially fed babies and their general health .
Lactulose is currently classified as a classic prebiotic. The general principle of its effect consists in reducing the amount of pathogenic bacteria, such as Escherichia coli and Staphylococcus. Moreover, lactulose stimulates the growth of probiotic bacteria, such as Bifidobacterium, which are known to produce a positive effect .
According to research data, the world production of lactulose preparations is currently 20 000 t/year, and over 5% of produced lactulose is used for this purpose. The assortment of lactulose preparations includes over ten items. Japan alone produces three types of syrups and two types of crystalline lactulose that satisfy the international quality standard .
The leading company in the world market of lactulose is Morinaga Milk Industry (Japan) dealing with the problems of studying the properties of lactulose and the development of methods for its production since 1953, i.e., for more than 60 years.
The market of lactulose in the Russian Federation has generally been represented by the pharmaceutical preparations of foreign production until now. OOO Shekhon-Laktuloze that produces lactulose syrup with a mass fraction of solids of no less than 66% is recognized to be the only large-capacity producer of lactulose in the Russian Federation.
It is considered that dry lactulose powders are more technological in use . However, the problem of the production of crystalline lactulose has not completely been solved in Russia until now. However, a number of technologies have already been patented.
According to patent data, the key problem in the existing technologies of the spray drying of lactulose solutions is the presence of binders, and the amorphous powder obtained at the outlet has high hygroscopicity. The analysis of the existing patented technologies and parameters of the drying of lactulose solutions is given in Table 1.
The analysis of the performed patent studies shows that among the disadvantages of the production of dry lactulose preparations by spray drying is a lowered content of lactulose in a product due to different catalysts and binders that are added to reduce hygroscopicity and accelerate the process. The growth of price due to the incorporation of fillers is also noteworthy.
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