Characterization of eucalyptus and citrus monofloral honey in São Paulo State by Thermoanalysis

Resumo

This work presents the optimization and development
of analytical methodologies for evaluation of glass transition
temperature (Tg) by DSC and for moisture and ash content
determinations by TG/DTG of honey samples. Beyond this, a
study of variability in these physicochemical parameters
determined by conventional methods was realized for eucalyptus
and citrus monofloral honeys of some regions of São Paulo
State.
For the thermogravimetric evaluation of honey samples, initially
a study of thermal behavior of standard of carbohydrates was
carried out by TG/DTG, DSC and DTA. The results obtained
allowed to distinguish the decomposition steps corresponding
to the sugars in relation to other components present in honey.
The variabilities in average moisture and ash contents of
eucalyptus and citrus monofloral honeys were investigated by
a hierarchical design and by an analysis of variance
(ANOVA).These physicochemical parameters are significantly
different at the 95% confidence level.
For the development and optimization of analytical
methodologies for moisture and ash contents in honey by TG/
DTG conventional methods, experimental designs and a F-test
for the comparison between variances were utilized . The results
suggest that to get average moisture and ash contents in honey
by TG/DTG similar to those found by conventional methods an
alumine crucible (150 µL), heating rates of 5ºC/min and microfiber
glass paper should be used. Besides this, the comparison
between the thermogravimetric method and the conventional
ones for these determinations suggest that there are no
significant differences between the methods investigated.
For eucalyptus and citrus monofloral honeys average glass
transition temperatures of – 47 and – 55ºC, respectively, were
determined suggesting a significant difference in this physical
property for these honey types. Besides this, a significant
negative linear correlation at 95% confidence level (r = - 0.916)
was verified between the moisture contents and glass
transition temperatures of these honey types. So, it may be
said that the physicochemical parameters, moisture and ash,
obtained by conventional and thermogravimetric methods and
the glass transition temperature determined by DSC can be
utilized for the characterization of the floral origin of these
types of honey.