Food Safety Magazine, August/September 2009

Some of these methods are time-consuming, and some are expensive. Although there are powerful methods to prove honey adulteration, they have to be further improved in order to ensure honey quality.

Due to the limitations of classical analytical methods, which measure chemical parameters to detect adulteration, many experiments have been carried out using new indicators derived from physical analysis, such as thermal analysis.

Differential Scanning Calorimetry

Differential scanning calorimetry (DSC) is a thermal analysis method with a broad field of application. It is an efficient method for characterizing pure food compounds as well as their mixtures. DSC analysis is fairly rapid and simple, requires a small

“Adulteration of pure honey with synthetic

honey (based on C4 plant sugars) has become much

more prevalent in recent years.”

NEW

Soya Tes t RAPID 3-D TM

Now Available

AUGUST ; SEPTEMBER 2009 amount of sample (< 100 mg) and does not use solvents. It has been used in monitoring thermal behavior in different foods, as well as in cases where no heat exchange occurs. DSC can monitor and determine heat flows resulting from various structural modifications (phase transformations and transitions, glass transition, etc.) or decomposition of food compounds, during temperature-programmed scans. These phenomena allow the determination of the type of transformation occurring in the studied food product (e.g., granulation in honey) as well as its thermodynamic and kinetic properties. DSC can be a useful technique to complement chemical analytical methods which show the limitations of the physicochemical determinations (i.e., pH, acidity, water activity and conductivity).

DSC has been investigated for the detection of alteration or adulteration, and for quality control of food. This technique was used to determine thermal behavior, energy variation during phase transition (crystallization or/and fusion), transition temperatures (such as glass transition temperature) and water content relationship in honey. Proper understanding of honey’s thermal properties is essential for defining honey quality and detecting its alteration or adulteration.

Honey is a viscous, heterogeneous material, which consists mostly of sugars ( present in an amorphous, devitrified state) and water (> 95%) and demonstrates certain thermal behavior during heat exchange. The thermal behavior of honey is influenced by several factors, including composition, temperature and amount and size of crystals. Knowledge of honey’s thermal behavior is critical during processing, handling and storage. Addition of syrups produces commercial honey of lower quality. When sugar syrups are added to authentic honeys, adulteration can be determined easily, since the syrups and honeys show significant differences in thermal phenomena, as well as in their amplitudes and positions on the temperature scale.

Honey and sugar syrups demonstrate several thermal or thermo-chemical parameters ( phenomena), such as the glass transition temperature (Tg), along with their re- Figure 1: Typical Features on a DSC Scan