New insights on the hard-to-boil massecuite phenomenon in raw sugar manufacture

Authors: Eggleston, Gillian; Cote, Gregory; Santee, Christopher

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2010
Publication Date: 5/1/2011
Citation: Eggleston, G., Cote, G., Santee, C. 2010. New insights on the hard-to-boil massecuite phenomenon in raw sugar manufacture. Food Chemistry. 126:21-30.

Interpretive Summary: Massecuites in sugarcane factories are mixtures of crystals in a sea of molasses. Sometimes after severe weather, massecuites are hard to boil (HTB), which this can cause factories to slow down considerably. Unfortunately, the specific cause of this problem was unknown. HTB massecuites and molasses were compared to normal samples, and could not transfer heat as well. Excess lime addition during juice clarification was shown not to be the direct cause of reduced ability to boil. A sophisticated viscosity technique showed that the HTB massecuites contained a gel network that trapped water explaining the difficulty in removing water on boiling. Other compounds such as mannitol (sugar alcohol) also contribute to the problem.

Technical Abstract: Hard-to-boil (HTB) massecuites (mixture of sucrose crystals in molasses) with markedly low heat transfer properties are a sporadic but continuing problem in sugarcane factories, which causes raw sugar and molasses production to decrease and increase, respectively. It usually occurs after severely deteriorated sugarcane has been processed, but the specific cause is unknown and only limited correction has occurred. At the end of the 2006 sugarcane processing season HTB and normal massecuites and molasses were collected from four Louisiana factories. Compared to normal samples, the HTB samples had 9.1-33.2% lower heat conductivity and 10.0-49.2% higher heat resistivity. The more HTB a sample is, then the greater the increase in heat resistivity compared to the corresponding decrease in heat conductivity. This strongly indicates substance(s) are responsible for suppressing heat transfer. Excess lime addition to neutralize acids during juice clarification is not the direct cause of hard boiling. Oscillatory deformation rheology was applied to the samples at 20 degrees C. Normal molasses samples gave typical mechanical spectra of concentrated solutions. In contrast, a highly viscous, intermolecular (gel) network was present in the HTB samples, which would explain the difficulty to remove entrapped water on boiling. One or more soluble polysaccharide(s) are likely the cause of the gel network. GPC, TLC, and methylation analyses suggested the presence of an arabinogalactan and endo-dextranase resistant dextran structures. The HTB phenomenon may have different causes and mannitol is a contributing factor. Additional research is required to find an economical processing aid that is capable of improving heat transfer and breaking down the intermolecular network in HTB samples at the factory.