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| Production of lactose | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Production of lactose | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| This section discusses the three major steps in the production of pharmaceutical lactose. These three steps are concentration, crystallisation and purification. Whey is the part of the milk that remains in the process ofproducing cheese. It consists mainly of water with whey-protein and carbohydrates (lactose). The milk fat and casein-protein go mainly into the cheese. During the processing of whey, the water and protein are removed, leaving lactose behind. The purification process, during which traces of protein and riboflavin are removed, results in pure, pharmaceutical-quality lactose.
Whey, as the remaining part of milk during the production of cheese, contains about 6% Dry Matter (DM). Concentration This whey is condensed by multi-stage vacuum evaporation to 60% DM, thereby reaching a temperature of 60°C. At this stage, the suspension is beyond saturation point. Crystallisation The supersaturated whey concentrate is cooled down in a stirred tank. During this cooling process, crystallisation takes place. The suspension is kept at this temperature for 24 hours to improve the yield of lactose. Centrifugation The crystallised concentrate is then transported to a decanting centrifuge. Due to the effect of centrifugal force, the wet edible lactose crystals are separated from the liquid protein fraction. During centrifugation, impurities are washed away with water from the lactose crystals. Wet edible lactose The wet edible lactose is centrifuged a second time to remove impurities such as minerals and protein. After that, it is dissolved in hot water until a suspension of 50% DM has been reached. Dissolving is necessary to enable filtration. The temperature will reach 95°C, and a pH of 4.6 will denature the last protein. Active carbon is added to decolourise the lactose solution by absorbing riboflavin. Purification & filtration To prevent the filter from plugging, filter aid is added to the lactose solution. The protein and active carbon are filtered off and a clear filtrate is obtained from the filter. Crystallisation The purified filtrate is brought to crystallisation by cooling down to 25°C for 6 hours. In such a ‘pure’ solution, seeding lactose is added to initiate the crystallisation process. Without seeding lactose, crystallisation will be very difficult because of the lack of ‘impurities’ in the solution. In this process, alpha-monohydrate crystals are formed. Centrifugation The crystallised filtrate is centrifuged to separate the crystals from the liquid. The end product is wet pharmaceutical lactose, with a Dry Matter content of 92%. The final product of the three major production steps (concentration, crystallisation and purification) is wet pharmaceutical lactose (containing 92% DM). This has to be dried before it can be used in pharmaceutical formulas. There are three major drying processes: fluid bed drying, roller-drying and spray-drying. These processes are quite different from one another and result in different end-products with different properties.
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