in carrying out the method of the invention , a natural water insoluble edible powder is suspended in a liquid . exemplary of the powders are water insoluble powders of cellulose , microcrystalline cellulose , cellulose derivatives , for example , ethyl cellulose , and starch and starch derivatives . advantageously the particles of powder will be in the range of from about 1 to about 50 microns . while the amount of powder for a given amount of water will vary widely , it is preferred that the powder be from about 2 % to about 15 % ( w / v ). advantageously , the liquid suspending medium may be water , or an aqueous solution , for example , an acid or a base to achieve a specific ph . the suspended powdered substrate is then dyed with an edible natural dye , for example , curcumin , turmeric , or an anthocyanin such as those contained in commercial grape skin extract . the dye may be added directly to the liquid in which the powder is suspended or may be first placed in a solvent to form a dye solution which is then added to the suspended powder . typically the solvent will be water but other solvents such as , for example , methyl alcohol , or ethyl alcohol may be used . advantageously an agent is employed to fix the dye onto the powder . exemplary of these agents are metal salts such as sodium chloride , aluminum chloride , and aluminum sulfate . inorganic acids such as , for example , hydrochloric acid may also be employed . except in the case of the inorganic acids , the fixing agent may be in an amount equal to from about 0 . 1 to about 10 % by weight of the powder in suspension . where the acidity of the suspension is relied upon to fix the dye to the powder through the use of an inorganic acid , it is preferred to have the ph from about 1 . 0 to about 5 . 0 . the dye per se or in solution is advantageously added to the suspension of the powder slowly while the suspension is stirred . the stirring is continued after all of the dye has been added for a sufficient period of time to fix the dye to the powder , generally from about 1 to 2 hours , depending on the particular dye . the suspension is then filtered and the recovered powder washed with water and dried to obtain the powdered natural dye pigment which has a particle size in the range of from about 1 micron to about 50 microns . while the powdered pigment can be air dried it is advantageous to carry out the drying in a mechanical convection oven at an elevated temperature of , for example , from about 40 ° c . to about 50 ° c . following the above method , fd & amp ; c and d & amp ; c lakes can be closely simulated using one or a mixture of pigments . a pigment made in accordance with the above method is normally placed in a suspending medium to form a stock suspension which is further diluted prior to application to the product to be colored . typically the suspending medium is an aqueous medium containing simple syrup u . s . p . and the pigment is present in an amount of from about 10 % to about 25 % ( w / v ). the dilution before coloring the selected product may be carried out with any standard syrup , for example , simple syrup , u . s . p ., the amount of dilution depending upon the intensity of color desired . advantageously the diluted suspending medium contains pigment in the amount of from about 1 % to about 5 % ( w / v ). then , for example , tablets are readily coated by placing the tablets in a coating pan and rotated . the diluted stock solution containing the pigment is added in a quantity sufficient to cover the tablets . the covered tablets are dried and the operation repeated until the tablets have the desired color . the invention will be further clarified by the following specific examples : 100 g of finely powdered microcrystalline cellulose is suspended in 1800 ml of water . 50 g of a 30 % ( w / v ) aluminum chloride in solution in water is added to the cellulose suspension and the suspension heated to 50 ° c . 10 g of curcumin is dissolved in 800 ml of water containing 3 . 2 g of sodium hydroxide to form a dye solution . the dye solution is then added in a fine stream to the microcrystalline cellulose suspension while stirring the suspension rapidly . stirring is continued until all the curcumin is attached to the microcrystalline cellulose particles ( 60 minutes ). the slurry is filtered , washed with water to remove any free dye not attached to the cellulose particles , and dried at 50 ° c . in a hot air oven to obtain a powdered natural dye pigment that simulates and may be substituted for fd & amp ; c yellow no . 5 aluminum lake . 100 g of finely powdered cellulose is suspended in 1800 ml of water . 15 g of aluminum sulfate powder is dissolved in the cellulose suspension and the suspension is then heated to about 50 ° c . 5 g turmeric is dissolved in 800 ml ethyl alcohol forming a dye solution . the turmeric dye solution is then added in a fine stream to the cellulose suspension while stirring the suspension rapidly . stirring is continued until all the turmeric is attached to the cellulose particles ( 60 minutes ). the slurry is filtered , washed with water and dried at 50 ° c . in a hot air oven , to obtain a powdered natural dye pigment of yellow - orange color . 100 g of finely powdered cellulose is suspended in 1800 ml of water . 10 g of water soluble annatto powder is dissolved in 800 ml of water and added to the cellulose suspension . the mass is heated to boiling and 25 g of sodium chloride is added to aid in the dyeing of the cellulose . the suspension is stirred for ten minutes , filtered , the cake washed with water and then washed with dilute acetic acid . the cake is then dried at 50 ° c . in a hot air oven to obtain a powdered natural pigment of red - orange color suitable for substitution for fd & amp ; c yellow no . 6 aluminum lake . 100 g cellulose is suspended in 1500 ml of water at room temperature . 25 g of a grape skin extract ( anthocyanins ) is added and the ph adjusted to 1 . 2 with hydrochloric acid . the suspension is then stirred for one hour , filtered and washed with ph 1 . 2 water . it is then air dried at room temperature to obtain a powdered natural pigment of bluish - red appearance . 100 g of finely powdered corn starch is suspended in 1800 ml of water . 50 g of a 30 % ( w / v ) aluminum chloride solution in water is added to the corn starch suspension and the suspension heated to 50 ° c . 10 g of curcumin is dissolved in 800 ml of water containing 3 . 2 g of sodium hydroxide to form a dye solution . the dye solution is then added in a fine stream to the corn starch suspension while stirring the suspension rapidly . stirring is continued until all the curcumin is attached to the corn starch particles ( 60 minutes ). the slurry is filtered , washed with water , and dried at 50 ° c . in a hot air oven to obtain a powdered natural dye pigment that simulates and may be substituted for fd & amp ; c yellow no . 5 aluminum lake . pharmaceutical tablets are made in accordance with the invention by placing pharmaceutical forms comprising a substrate containing a medicament into a coating pan , making a color dispersion by mixing 15 g of natural dye pigment of example i and 10 g of titanium dioxide with 75 g of simple syrup , u . s . p ., further diluting the dispersion by adding 900 g of simple syrup , u . s . p ., rotating the coating pan , repeatedly adding portions of the diluted color dispersion to the coating pan to coat the substrates , and drying and polishing the coated tablets .
a pharmaceutical tablet consists of a substrate containing a medicament and may be covered with a coating , said coating including a pigment comprising a natural water insoluble edible powder dyed with an edible natural dye . the pigment for coloring the tablet , or other pharmaceutical products , as well as food and cosmetics , is made by suspending a natural water insoluble edible powdered substrate in an aqueous vehicle and dyeing the suspended powdered substrate with an edible natural dye . the liquid is removed to obtain the dry pigment powder of the invention which then can be suspended in a suspending medium and used for coating products to be colored such as food , drug and cosmetic products .