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  • Author: Sławomir Bakier x
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Sławomir Bakier, Krzysztof Miastkowski and Jan Robert Bakoniuk

Abstract

The paper presents the results of rheological measurements conducted on three types of Polish honey: rape, multi-floral, and buckwheat honeys. The investigations involved identification of the properties of the honeys in both liquefied (by heating) as well as crystallised states. Both steady shear as well as dynamic rheological tests were performed. As a result, it was possible to show that the liquefied honeys behave like Newtonian fluids. Good agreement of the results between the rotary shear and oscillation rotary tests was observed, thus fulfilling the Cox-Mertz rule. The structure of the honeys was subjected to qualitative scrutiny by analysing photographs of the crystals taken in the conditions of shearing interferometry. The quantitative analysis was made by presenting a numerical distribution of crystal colonies with reference to the maximum dimensions of individual crystals. The geometric measurements of the crystals were carried out using analiSIS software. In the crystallised form, the media showed a thixotropic effect, and their apparent viscosity was many times higher than the dynamic viscosity in the liquid state. After plasticising by deformation with an increasing shear rate of up to 450s−1, the equilibrium melting curves of the crystallised honeys were described by the Ostwald-de Waele model. One particular reason for the research was to show that the results obtained for the honeys crystallised by the steady shear method, were qualitatively different from the results obtained in the dynamic measurements. The Cox-Mertz rule cannot be applied for the crystallised honeys.

Open access

Jolanta Tomaszewska-Gras, Sławomir Bakier, Kamila Goderska and Krzysztof Mansfeld

Abstract

Thermodynamic properties of selected honeys: glass transition temperature (Tg), the change in specifi c heat capacity (ΔCp), and enthalpy (ΔH) were analysed using differential scanning calorimetry (DSC) in relation to the composition i.e. water and sugar content. Glass transition temperatures (Tg) of various types of honey differed significantly (p<0.05) and ranged from -49.7°C (polyfloral) to -34.8°C (sunflower). There was a strong correlation between the Tg values and the moisture content in honey (r = -0.94). The degree of crystallisation of the honey also influenced the Tg values. It has been shown that the presence or absence of sugar crystals influenced the glass transition temperature. For the decrystallised honeys, the Tg values were 6 to 11°C lower than for the crystallised honeys. The more crystallised a honey was, the greater the temperature difference was between the decrystallised and crystallized honey. In conclusion, to obtain reliable DSC results, it is crucial to measure the glass transition after the complete liquefaction of honey.

Open access

Valery A. Isidorov, Sławomir Bakier and Marcin Stocki

Abstract

Honeybee larva homogenate appears to be underrated and insufficiently explored but this homogenate is an exceptionally valuable honeybee product. Drone larva homogenate is very nutritional due to its high content of proteins, free amino acids, lipids, and carbohydrates. Moreover, the biological characteristics of honeybee larvae indicate the presence of chemical substances that may be pharmacologically active. In spite of the above, the chemical composition of honeybee larva has not gained as much attention as that of other bee products. In this study, the chemical composition of honeybee brood homogenate has been investigated using gas chromatography/mass spectrometry. As a result, it was possible to isolate as many as 115 extractive organic compounds from 6 samples of crude queen and 9 samples of drone homogenate. The main groups of substances extracted from either type of homogenate were composed of free amino acids and carbohydrates. The relative content of amino acids in queen homogenate as well as the share of essential amino acids were found to be higher than in the drone homogenate. Disaccharide trehalose was the dominant sugar in the queen larvae, whilst glucose prevailed in the drone larvae. Comparative chemical analyses of honeybee queen and drone larva homogenates have allowed us to make a preliminary inference about a higher overall value of the former.