Evaluating the Potential of Juice from Some Sweet Sorghum Varieties Grown In Kenya to Crystallize

Abstract

Sweet sorghum (Sorghum bicolor (L) Moench) is a crop analogous to sugarcane with similar accumulation of sugars in its juicy stems. An earlier research study on agronomic trials carried out by Jomo Kenyatta University of Agriculture and Technology established that some of the imported varieties of Sweet Sorghum had sufficiently high amounts of sugar content in their Juice. The present study was undertaken with the objective of determining the potential of some of these sweet sorghum varieties to produce crystal sugar. This was with the long term goal of trying to find alternative uses for sweet sorghum. The sweet sorghum varieties were planted at the University research farm, and stalks of sixteen varieties were crushed using electrical roller mill to produce SS juice which was then subjected to a number of analyses including, total and specific sugar determination and apparent purity. The total sugars in degree Brix varied from 15.05⁰ to 21.50⁰, sucrose concentration ranged from 6.05g/l to72.77g/l, glucose 2.65g/l to 16.41g/l and fructose 2.66g/l to 17.16g/l whereas apparent purity(AP) ranged from 33.89% to 83.91%.The variation could have been  brought about by varietal differences. The juice of variety RIO had the highest sucrose purity of 83.91% which was further clarified by liming and double carbonation method. The resulting juice was concentrated into syrup by evaporation. Supersaturation for crystallization was attained by cooling, followed by seeding. According to the present study, the following sweet sorghum cultivars; Rio, CMSXS636, IESV91018LT, IESV93042SH and SPV1411 could have potential in crystal raw sugar production because they have AP greater than 75% and a relatively higher sucrose concentration. The Rio sweet sorghum variety with the highest sucrose purity of 83.91% and sucrose concentration of 40.86g/l was selected and subjected to crystal sugar production processes. The Rio juice subjected to crystallization process failed to produce crystals probably due to the presence of dextran, aconitic acid and starch.

Key words: Brix, Sucrose, apparent purity, Clarification, Crystal Sugar,