Group B2 - Assignment 1Properties for Processing. Riboflavin (vitamin B2) is isolated by filtration and polishing by spray drying. The efficiency of both processes (higher yield per unit time) increases with increasing temperature. Find the necessary handbook data and determine the maximum temperature at which u could run these two unit operation.

Vitamin B2 or riboflavin importance in functioning metabolic system concerned with the oxidation of carbohydrates and amino acids. It is not in the free form but in more complex compound known as coenzymes, such as mononucleotide (FMN) and flavin adenine dinucleotide (FAD), or flavoprotein. It plays an important role in energy metabolism of fats, ketone bodies, carbohydrates and proteins.

Figure 1: Chemical Structure of Vitamin B2 (Takayuki et al., 1999).

The process for the purification of riboflavin (vitamin B2) is particularly suitable for the removal of DNA associated with riboflavin crystals. Riboflavin is produced by microorganisms and the pure product is obtained by consecutive purification steps starting from the crude reaction slurry (fermentation broth) containing the riboflavin. The process for the purification of riboflavin comprising the steps below:(a) Precipitating a first crystalline form of riboflavin,(b) Isolating the first crystalline form of riboflavin,(c) Transforming the first crystalline form of riboflavin into a second crystalline form of riboflavin under conditions that decompose diluted DNA, and(d) Isolating the second crystalline form of riboflavin, provided that at ambient temperature (which is average room temperature, preferably 23C) the first crystalline form of riboflavin is thermodynamically less stable than the second crystalline form of riboflavin.

Depending on the temperature the following crystalline forms are in equilibrium with one another or are irreversibly transformed into each other under defined conditions: riboflavin anhydrate I with riboflavin dihydrate and riboflavin tetrahydrate; riboflavin anhydrate II with riboflavin monohydrate and riboflavin dihydrate; riboflavin anhydrate III with riboflavin tetrahydrate.At 23C, riboflavin anhydrate I and riboflavin dihydrate can be illustrated as follows:

At 23C, the equilibrium between riboflavin anhydrate I and riboflavin dihydrate is completely shifted to the side of riboflavin anhydrate I. At this temperature riboflavin dihydrate is irreversibly transformed into riboflavin anhydrate I. Thus, at 23C no riboflavin dihydrate can be obtained from pure riboflavin anhydrate I. At higher temperatures 39C, riboflavin dihydrate is thermodynamically less stable than riboflavin anhydrate I.At 23C, the kinetic of the transformation of riboflavin dihydrate into riboflavin anhydrate I is slow. Stirring a slurry containing pure riboflavin dihydrate at a temperature of 23C results in a partial transformation (80%) into riboflavin anhydrate I in 2 days (determined by Raman spectroscopy). At 39C, the differences of the solubility or the chemical potentials are small. Therefore, at this temperature the transformation of riboflavin dihydrate to riboflavin anhydrate I is slow.At higher temperatures, the difference between the chemical potentials of riboflavin anhydrate I and riboflavin dihydrate increases. Therefore, the velocity of the transformation process significantly increases, as riboflavin dihydrate is completely transformed into riboflavin anhydrate I within 20 seconds at 80C.However, at 4C the thermodynamic situation is different. In an aqueous slurry riboflavin anhydrate I can be transformed into riboflavin dihydrate, the latter being irreversibly obtainable from riboflavin tetrahydrate (particularly at higher temperatures):

At 4C, the kinetic of the transformation of riboflavin anhydrate I into riboflavin dihydrate is very slow. Stirring a slurry only containing riboflavin anhydrate I at a temperature of 4 C leads to a partial transformation (80%) of riboflavin anhydrate I into riboflavin dihydrate in 56 days.

Riboflavin: Decomposes at 278-282C (darkens at about 240C)

A method for producing a granulated riboflavin product comprises making a specific mixture of riboflavin, binder and water, followed by homogenizing the mixture and thereafter spray-drying the homogenized mixture so that granules are produced. Using a laboratory size spray-drying apparatus, the previously prepared homogenized riboflavin suspension was metered to the atomizing wheel. The atomizing wheel (a slotted wheel obtained from Niro Atomizers, Inc., 9165 Rumsey Road, Columbia, Md., as used in utility dryer Model IV) was operated at 21,000 rpms, a centrifugal speed of about 8,000 meters per minute. The inlet air temperature flowing into the spray dryer chamber was about 200 C., and the outlet air temperature was about 100 C. The riboflavin suspension was fed into the spray atomizing wheel at a rate of about 125 grams per minute. The resulting riboflavin powder was an orange, free-flowing, static-free powder having a bulk density of 0.43 grams per cubic centimeter with a geometric mean particle size of about 58 microns and a log standard deviation of about 1.5 microns. Furthermore, the powder had a flowability index (as measured by the Flodex method) of at least 333. [A flowability index greater than 100 is indicative of excellent flowability.] This powder mixed well in flour premixes and produced directly compressible tablets with the hardness of 12 scu. The final product was made up of about 94 weight percent riboflavin, 5 weight percent binder, and 1 weight percent water.In conclusion, the optimum temperature to spray-dry the riboflavin is 200, which lead to the production of 94 weight% of granulated riboflavin. From Merck Index, riboflavin decompose at the range from 278 to 282, and darken at 240. This mean that, the maximum temperature to crystalize riboflavin is in the range between 230and 239.

Reference:O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, andBiologicals. Whitehouse Station, NJ: Merck and Co., Inc., 2006., p. 1413

Process for spray drying riboflavin to produce a granulate product having low binder content(n.d.). Retrieved on 8 March, 2015 from https://www.google.com/patents/US5000888