Effect of drying methods on the physicochemical and bioactivities of bovine colostrum and lactoferrin : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Auckland, New Zealand
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Date
2024
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Massey University
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Abstract
The aim of this study was to use low temperature electrostatic spray drying to produce bovine colostrum and lactoferrin powders with improved functional properties. The objectives were to examine the effects of spray, freeze and electrostatic spray drying on the physicochemical properties, bioactivity, antimicrobial and antioxidant activity of the bovine colostrum and lactoferrin. Liquid bovine colostrum and lactoferrin was spray dried at two different inlet temperatures: 165 and 180℃ and was electrostatic spray dried at two lower inlet temperatures: 75 and 150℃. Powders collected were analysed for the following characteristics: moisture content, water activity, crude protein content, solubility, particle size, absorbance spectrum from Fourier transform infrared spectrophotometry (FTIR), bioactive immunoglobulin and lactoferrin content (enzyme-linked immunosorbent assay (ELISA)) bioactivity, iron-binding ability (two methods), antioxidant ability using 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability and antimicrobial ability. All analysed colostrum and lactoferrin powders had a moisture content below 4.5% (w/w) and water activity below 2.6. There was generally a decrease in the moisture content and water activity with increasing drying temperature. Drying temperatures also had an effect on the powder solubility and particle size. With higher drying temperatures, the solubility and volumetric median particle size (Dv50) of the powders decreased. The secondary structure of the protein investigated using FTIR showed that high temperature spray dried colostrum had greater protein degradation than low temperature electrostatic spray dried. ELISA analysis indicated that electrostatic spray dried colostrum retained more bioactive lactoferrin protein than freeze dried or high temperature spray dried. From both iron-binding methods tested, found that high temperature spray dried and low temperature electrostatic spray dried colostrum and lactoferrin had similar iron-bind ratios, ranging between 3 to 4 moles Fe/moles protein for colostrum, and 1.3 to 1.5 moles Fe/moles protein for lactoferrin. Low temperature electrostatic spray dried colostrum and lactoferrin showed better DPPH radical scavenging ability, followed by freeze dried and lastly high temperature spray dried. Colostrum electrostatic spray dried at 75C and freeze dried lactoferrin showed better antimicrobial ability to Escherichia coli and Staphylococcus aureus than others. In conclusion, low temperature electrostatic spray drying was able to produce bovine colostrum and lactoferrin powders with slightly better bioactive and functional properties.
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