Evaluation of vacuum kettle processing of sorghum syrup

A 19-liter steam-jacketed, stainless steel kettle was modified to simulate a vacuum pan for use in the processing of sweet sorghum (Sorghum bicolor (L.) Moench) syrup. The vacuum-processed syrup was compared to syrup processed in a conventional 224-liter, black-iron evaporator pan. The comparison consisted of chemical and physical analyses, as well as a taste preference panel. The experimental design, a randomized complete block design with factorial arrangement of treatment combinations, consisted of five replications with seven treatments per replication. Treatments consisted of combinations of vacuum level and the degrees Brix of the juice or semi-syrup when introduced to the vacuum kettle. The chemical and physical analyses of the syrup included a determination of degrees Brix, pH, total solids, extraneous materials, percentage ash, and titratable acidity. The taste preference panel compared the conventionally prepared syrup to the vacuum-processed syrup in terms of texture, flavor, and color. Statistical analyses of the taste preference panel data results indicated that the panel perceived no significant differences in the conventionally processed and the vacuum-processed syrup in terms of texture, flavor, and color. Statistical analyses of the physical and the chemical analyses data indicated a replication effect and a vacuum level, replication interaction effect on pH. There was also a significant replication effect on the extraneous material. The degrees Brix level to which the syrup was concentrated had a significant effect on total solids. Also, a significant replication effect on total solids was exhibited. A significant vacuum level effect on acidity level was noted. As the vacuum level was increased, the percentage titratable acidity increased.