Effects of Drying Conditions on Protein Properties of Blood meal
Damba, C. (2017). Effects of Drying Conditions on Protein Properties of Blood meal (Thesis, Master of Science (Technology) (MSc(Tech))). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/11345
Permanent Research Commons link: https://hdl.handle.net/10289/11345
Blood meal is a by-product of the meat industry produced through drying of animal blood. It contains about 85 wt.% proteins. Drying has been used as a method to preserve biomaterials and involves lowering of the water activity of biomaterials. The purpose of this research was to study the drying kinetics of producing blood meal in an oven dryer, to evaluate suitable drying models for describing the drying process and to determine the effects of drying conditions on the physio-chemical properties of blood meal. Moisture content and drying rates were determined by drying coagulated blood at different temperatures (60 °C, 100 °C and 140 °C) for a constant period of 24 hours. The initial moisture content of coagulated blood was about 60.7 wt% on a wet basis. A drying temperature of 140 °C was found to be the optimal for routine moisture determination for coagulated blood as equilibrium moisture was achieved within 24 hours period. A constant drying rate period was not observed in any of the conditions tested, and the initial increasing rate period as followed by a short transition phase prior to the falling-rate period. Thus, moisture removal from the coagulated blood was governed by a diffusion-controlled process. The experimental drying data for coagulated blood was used to fit the Lewis, Page, Modified Page, Logarithmic and Henderson and Pabis models and the statistical validity of models tested were determined by non-linear regression analysis. The Page model had the highest R² (0.9999) and lowest χ² (0.0001) and RMSE values. This indicated that Page model adequately described the oven drying behaviour of coagulated blood. Blood meal samples were produced by drying coagulated blood at different temperatures (60 °C, 100 °C, 140 °C) to varying moisture contents (5 %, 10 % and 15 %). A drop penetration test using water and/or sodium dodecyl sulphate dissolved in water were used to determine the wettability of the samples produce while thermal analysis techniques such as Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) were used to investigate the thermal properties of bloodmeal. X-ray scattering was used to investigate conformational changes in blood meal proteins during drying. Drying conditions had substantial effects on both physicochemical and thermal properties of blood meal. It was established that drying temperature had a more significant effect on the wettability of blood meal than the final moisture content. However, the final moisture content had larger contribution to the thermal stability of blood meal than drying temperature. Blood meal produced at 60 °C to 15% moisture content was the most stable sample while blood meal produced at 140 °C to 10% moisture content was the least stable. Protein denaturation was observed at 92 °C to 122 °C, depending on moisture content and drying temperature. DMA results revealed that different relaxations occurred when drying coagulated blood. A dry glass transition temperature for samples was observed between 219 °C - 226.8 °C. This suggested that bound water does not act as plasticiser in blood meal. Glass transitions observed in DSC were therefore, considered more accurate and reliable for blood meal samples containing moisture. Drying of coagulated blood was observed to have drastic effect on the structural arrangement of coagulated blood in XRD. Increase in moisture content was observed to have an effect on the β-sheets structure of samples dried at 60 °C and 100 °C. Since bloodmeal produced at 60 °C and 100 °C did not show complete denaturation of proteins, future thermoplastic processing should consider blood meal produced within this temperature range for improved properties.
The University of Waikato
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