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Sugar Boiling in Sugar Crystallization Process
- 1. SUGAR BOILING By G.Kiruthika Assistant Professor Department of Food Technology
- 2. Sugar boiling •Maximum recovery of sucrose by crystallization cant be achieved by one step •The limit to crystal content is met at a point where the massecuite will no longer flow out the pan •Crystallization is stopped before this point from molasses •The molasses produced still contains crystallizable sugar and the process is repeated in one or two stages for optimal sugar recovery •The purity of massecuite decreases with each sucessive stages as more sucrose is removed •Various crystallization scheme is employed to suite the purity of the syrup and quality of the sugar produced The following schemes are mostly used •Two-boiling scheme •Three- boiling scheme •Double einwurf scheme •VHP scheme
- 3. Two-boiling scheme •The main advantage of two stage crystallization system is simplification of the equipment needed by elimination of B sugar stage •This scheme does not appreciably change the total volume of massecutive to be boiled •A molasses is used as a for C massecuites •It is centrifuged in continuous centrifuges nd it is made into a magma of about 85 purity •The sugar is crystallized from C magma seed •The massecuite must be thoroughly exhausted in the pan and cooling crystallizers to obtain a purity drop of at least 20 poits between masecuite and runoff syrup •The purity cant be lowered to exceed 80-82 if the required purity drops between A massecuite and final molasses •It is achieved in two step. Back-boiling of A molasses onto the A strike in case of higher syrup purities and the scheme is better suited for low purity syrup •Crystallization from the lower point of low purity •Massecuite yields the sugar higher in color •For this reason two stage crystallization must be used
- 5. Three- boiling scheme •Most commonly used in three stage crystallization scheme with both A abd B sugar for sale •Sugar is crystallized from syrup using a seed magma consisting of C sugar in water having a purity of about 85 and A also has the same purity as syrup •The massecuite is centrifuged to obtain A sugar of relatively high pol (98-99 · Z)is mixed with the A sugar and expired from a factory •The footing for the C seed consist of mixture of A molasses and Syrup at about 70 purity or between 70-60 purity •The C massecuite boiling is fed with B molasses and the C msecuite is centrifuged in continuous centrifuges to yield C sugar and final molasses •The C sugar at about 85 purity is mixed into magma which is used as seed fro the A and B crystallization stage •The B purity is higher than a due to the influence of C seed magma but also the addition of syrup to reduce viscosity •The purity has to be kept in the 70-75 range to obtain B sugar of 98· Z with relatively large crystals and acceptance from batch centrifugals •High B massecuite purity results in high run-off syrup purity and final molasses purity this is the main dis-advantage of this scheme
- 7. Double Einwurf scheme •This is some times called as double magma or CBA scheme •This three-stage crystallization scheme uses the C sugar as the nucleus for B sugar and B sugar as a nucleus for A sugar •Preparation of C sugar is same as for three-boiling scheme and is centrifuged in continuous centrifuge •C sugar is made into magma with water or clarified juice and is used as a seed for B sugar •B sugar is crystallized from A molasses and centrifuged continuously and B sugar is also made into B magma •Sugar is crystallized from syrup with seed magma of B syrup and centrifuge d in batch •An excess of either dissolved and returned to syrup as remelt Advantage •Production of single grade first quality sugar •Continuous centrifuge on B sugar •It is rich in color and ash content Dis-advantage •High purity of B is caused by seed magma •Control of crystal size B and C is critical to avoid having excess sugar
- 9. VHP scheme •This modification of three stage crystallization scheme is widely used •Very high polarization (VHP) sugar of 99.3 to 99.5 · Z •All the C sugar is dissolved in water or clarified juice and sent back to the syrup tank as remelt •C sugar of 81 to 85 purity is obtained by single centrifugation in continuous centrifuges •The B sugar is Produced by seeding a 60-70 purity mixture of A and B molasses and feeding a strike with A molasses •The B molasses is centrifuged in continuous centrifuge to obtain sugar of about 90 to 92 purity which is made into a magma and used for a seed for A crystallization •Any excess B sugar is dissolved and returned to the syrup tank as remelt