II. Production Methods 805After conversion to the proper DE, the reaction is stopped in the neutralizer tankby raising the pH with soda ash (sodium carbonate) to 4.5 – 5.0. This pH is critical notonly to optimize the conditions under which the proteins and fats can be removed,but also to reduce the risk of unnecessary color development. At this point, the liquormay be pumped to an enzyme tank for further enzyme-catalyzed conversion, or clari-fi ed, bleached and evaporated.If the liquor is not to be enzyme-converted, it is pumped to ‘ mud ’ centrifuges androtary drum fi lters which remove the suspended fats and insoluble impurities fromthe fi ltrate. Amino acids and peptides which may react with carbohydrates are alsoremoved. Then the fi ltrate is passed through pulsed beds of activated carbon forclarifi cation and bleaching. The temperature in the carbon column is maintained at150 – 170 ° F (69 – 77 ° C) with a typical contact time of 90 – 120 minutes for optimumremoval of impurities. Usually these columns contain packed granular carbon,although powdered carbon may also be used.It has long been known that activated carbon removes color precursors and offfl avors and is particularly effective in removing 5-(hydroxymethyl)-2-furaldehyde(HMF), a glucose decomposition product created during acid-catalyzed hydrolysis. 23In typical systems, as shown in Figure 21.5 , the carbon beds are used in a counterfl owfashion in which the spent carbon is removed, regenerated in a furnace and repackedat the top of the column. 24 After the carbon beds, the liquor is passed through ‘ check ’fi lters designed to remove escaping carbon fi nes.Some syrups are ion-exchanged at this point in the process. Ion exchange is essentialin the production of certain types of sweeteners, such as high fructose syrups.Not only does ion exchange improve the color and color stability of the syrup by
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