The thermophysical properties of model systems of hydrocolloids and sugars

Cilj rada bio je ispitati termofizička svojstva modelnih sustava hidrokoloida (guara, ksantana) i šećera (saharoze, trehaloze) u temperaturnom području od -60 °C do 140 °C. Termička analiza uzoraka provedena je pomoću diferencijalnog motridbenog kalorimetra, a praćeni su parametri staklastog prijelaza, kristalizacije i taljenja. Iz rezultata se može zaključiti da su temperature faznih prijelaza kod istovrsnih sustava bile niže, što je viši udio suhe tvari. U modelnim sustavima ksantan-trehaloza razlika u srednjoj (midpoint) temperaturi staklastog prijelaza između sustava (0,6 % ksantana + 30 % trehaloze) i (0,6 % ksantana + 50 % trehaloze) iznosila je 2 °C, a u sustavima guar-trehaloza pri istim koncentracijama i manja (1,3 °C). U modelnim sustavima ksantan-saharoza pad srednje temperature staklastog prijelaza kod spomenutih koncentracija bio je 6,2 °C, odnosno 6,7 °C u sustavu guar-saharoza. Povećanjem udjela suhe tvari (dodavanjem šećera) došlo je do sniženja vrijednosti entalpija faznih prijelaza u svim uzorcima, a vrijednosti su niže u sustavima sa saharozom. U ispitivanim modelnim sustavima nije bilo značajne razlike u DSC parametrima između hidrokoloida.The aim of this study was to investigate the thermophysical properties of model systems of hydrocolloids (guar, xanthan) and sugars (sucrose, trehalose) in a temperature range from -60 °C to 140 °C. Thermal analysis of samples was performed using a differential scanning calorimeter, and the parameters of the glass transition, crystallization and melting were studied. The findings of this study indicate that the temperatures of phase transitions at the same systems were lower, with the higher the proportion of dry matter. In model systems of xanthan and trehalose difference in the midpoint glass transition temperature between the system (0.6% of xanthan + 30% trehalose) and (0.6% of xanthan + 50% trehalose) was 2 °C, and in the systems guar- trehalose at the same concentrations and lower (1.3 °C). In model systems of xanthan-sucrose drop of midpoint glass transition temperature in the mentioned concentration was 6.2 °C, and 6.7 °C in the system guar-sucrose. By increasing the content of dry substance (addition of sugars) values of the enthalpy of phase transitions in all samples were decreased. The values are lower in the system with sucrose. In the tested model systems there were no significant differences in the DSC parameters between hydrocolloids