Investigating the thermal behavior differences between beet and cane sugar sources

Thermal behavior;beet and cane sucrose

Lu, Yingshuang

关键词: Thermal behavior;    beet and cane sucrose;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/90912/LU-DISSERTATION-2016.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The melting behavior of sucrose has been well studied over a long period of time. However, one aspect that needed further study was the wide variation in melting temperature reported in the literature for sucrose, as well as other simple sugars (e.g., glucose and fructose). Based on previous work carried out in the Schmidt laboratory, the initial loss of crystalline structure in sucrose, glucose, and fructose was attributed to thermal decomposition, rather than thermodynamic melting. Recently, a number of sucrose samples were investigated in the Schmidt laboratory and a marked difference in the thermal behavior of beet versus cane sucrose samples was observed. In general, sucrose from sugarcane sources exhibited two endothermic peaks in the DSC thermogram, one small peak proceeded by one large peak; whereas, sucrose from sugarbeet sources exhibited only one large endothermic peak. The thermal behavior of both beet and cane sucrose sources also exhibited heating rate dependency, with Tmonset values for both small and large peaks increasing as heating rate increased. Overall, however, the degree of thermal stability, based on results from an ampule heating study, was much greater for beet compared to cane sucrose sources. To date, no published research was found relating the presence and magnitude of the small endothermic DSC peak to the plant source of the sucrose – suagrbeet versus sugarcane. Thus, the main objective of this research was to identify the cause and underlying mechanism of the presence of the small endothermic DSC peak in cane sucrose sources. A variety of analytical methods and techniques were applied to approach this research objective, including moisture content analysis, pH, conductivity ash content, total sulfite content measurements, single crystal X-ray diffraction (SXRD), X-ray Micro-Computed Tomography (MicroCT), Differential Scanning Calorimetry (DSC), High Performance Liquid Chromatography (HPLC), and Confocal Raman imaging and spectroscopy. From this study we found that the pH, conductivity ash, and moisture content values varied widely within and between sugar sources, and were not able to explain the small endothermic DSC peak difference between beet and cane sucrose sources. However, impurities in the mother liquor occlusions in beet, Chinese cane, and Sugar in the Raw appear to play a major role in thermally stabilizing the sucrose molecule. Beet and Chinese cane sucrose sources contained residual sulfite from the sulfitization processing step; whereas, analytical and commercial cane sources, which usually do not undergo sulfitization, were below the detection limit. Thus, sulfite content appears to explain the absence of the small endothermic DSC peak. Also, by addition of different concentrations of potassium sulfite, we were able to control the thermal behavior of laboratory-recrystallized Sigma sucrose, demonstrating that low concentrations of sulfite can completely inhibit the small endothermic DSC peak in cane sources. In the case of Sugar in the Raw, the high conductivity ash and pH appear to be responsible for inhibition of the small endothermic DSC peak. Overall, this research reveals that the composition and chemistry of the mother liquor occlusions, formed within the sucrose crystal during the crystallization process, are responsible for the thermal behavior of the various sucrose sources studied herein, In addition, this study makes a substantial contribution to the investigation of the thermal behavior of crystalline sucrose at the molecular level, since no previous research was found that explored the internal crystalline structure and vibrational modes of “as is” and heated crystalline beet and cane sucrose sources, which were examined using Micro-CT and Confocal Raman imaging and spectroscopy, respectively. Overall, this research provides a comprehensive and more detailed understanding of the thermal behavior of sucrose, regardless of its source, which, in turn, is critical to the processing of and reactions in sucrose containing foods, such as baking and caramelization.