Glass Transition and Crystallization of Amorphous Trehalose-sucrose Mixtures

Abstract

Our objective was to investigate the glass transition and crystallization of trehalose-sucrose mixtures at various moisture contents. Samples were freeze-dried, rehumidified, and scanned with Differential scanning calorimetry (DSC) to obtain T g values for all mixtures and pure sugars. Amorphous cotton candy samples for crystallization studies were prepared, humidified, and monitored for crystallinity as a function of time using powder X-ray diffraction (XRD). The T g of pure dry trehalose was found to be 106 °C, while sucrose had a T g of 60 °C. Glass transition, as expected, occurred at an intermediate temperature for sucrose-trehalose mixtures. Of the dry samples, only those containing less than 16% trehalose showed sucrose crystallization during scanning. In cotton candy made from a 25% trehalose-75% sucrose mixture, humidified to 33%, sucrose did not crystallize after 30 days, whereas pure sucrose cotton candy at that humidity crystallized completely after 11 days. These data show that trehalose may be a useful crystallization inhibitor in foods with high sucrose content, although small amounts of trehalose did not significantly raise the T g .

Crystallization inhibition of an amorphous sucrose system using raffinose

“…See Roe and Labuza (2006) for a tabulation of sucrose values showing that raffinose had very little effect on changing the T g at 11%RH and 33%RH as compared to pure sucrose, the differences are not meaningful. Note that Roe and Labuza (2006) found that trehalose raised the T g of the mixtures albeit being added at a higher percent. The glass transition temperature for the 5%-R:95%-S mixture at the 43%RH chamber was not detectable perhaps because of the lower sensitivity at 10 °C/min rate.…”

“…Smythe (1967) and Iglesias et al(2000) also found that raffinose slows the crystallization of sucrose in aqueous solutions and that the optimal equilibrium state of crystalline raffinose is as a pentahydrate form, therefore, a relatively large amount of water is needed to completely crystallize it. Pure raffinose also has a higher glass transition temperature as compared to pure sucrose and may work in the same way trehalose inhibited crystallization of sucrose as found by Roe and Labuza (2006). The objective of this study was to determine whether raffinose would inhibit or slow the crystallization of sucrose from the amorphous solid state of a glassy material, cotton candy, when held above and below the glass transition temperature.…”

“…It was thought that trehalose would interrupt the crystallization of sucrose because trehalose has a higher glass transition temperature as compared to sucrose. Roe and Labuza (2006) found that 100% sucrose system crystallized after 11 d when stored at room temperature and 33%RH. Cotton candy made with 25% trehalose and 75% sucrose stored at room temperature and 33%RH collapsed, but did not become crystalline even after 26 d. It was also found that at room temperature and 54%RH, after 46 h, the system containing 25% trehalose and 75% sucrose was not crystalline, but that the 100% sucrose system was fully crystallized.…”

“…Roe and Labuza (2006) conducted such a study to observe the Journal of Zhejiang University SCIENCE B ISSN 1673-1581 http://www.zju.edu.cn/jzus E-mail: jzus@zju.edu.cn effects of trehalose on the crystallization of sucrose in cotton candy and a freeze dried sucrose/trehalose mixture. It was thought that trehalose would interrupt the crystallization of sucrose because trehalose has a higher glass transition temperature as compared to sucrose.…”

Fructose-rich syrup from Ghars cultivar dates (Phoenix dactylifera L.)

“…Crystallization of glucose was achieved by storage of prepared syrup at 4°C for more than 70 days (Roe and Labuza, 2006). The crystals which formed were then removed by sieving with a 1mm filter to produce the modified syrup.…”