Reconstruction of milk fat globules/membrane (MFGs/MFGM) and characterization of its physicochemical properties and techno-functionalities
Loading...
Files
Full Text E-thesis
Date
2024
Authors
Sun, Yanjun
Journal Title
Journal ISSN
Volume Title
Publisher
University College Cork
Published Version
Abstract
Most commercially available infant formulas (IFs) lack phospholipids and milk fat globule membrane (MFGM) proteins. To mimic human milk's lipid profile, MFGs/MFGM ingredients from sweet whey or buttermilk are fortified in IF. Understanding the structural and compositional, and techno-functionalities changes of MFGs/MFGM is crucial for their application.
The MFGs/MFGM has been reconstructed by the mostly used processing methods in dairy industry, acidification (pH 6.30 and 5.30, 25℃), and novel non-thermal treatment, ultrasonic treatments with different intensities. Additionally, anionic polysaccharide- high-methoxyl pectin (HMP) was incorporated to the raw milk before the cream separation, examining the resulting physicochemical properties and techno-functionalities.
Results indicated that pH adjustment affected the MFGs structure and MFGM protein compositions, particularly at pH 5.30, causing protein loss such as butyrophilin (BTN) and Periodic Acid Schiff 6/7 (PAS 6/7) and particle size changes. Fourier Transform Infrared Spectroscopy (FTIR) spectra revealed more proteins compositions in MFGs/MFGM prepared from sweet whey (MFGM-C) compared to bovine raw milk, showing lower interfacial tension and ζ- potential. In addition, there were no apparent polymorphs in MFGM-C, and lower exothermic or endothermic enthalpy was needed during the heating and quenching procedures. Acidification, especially pH 6.30 conditions, led to the adsorption of non-membrane milk proteins on the MFGs or MFGM fragments and formed more types of conjugate detected by FTIR. Consequently, this induced changes in the crystal form proportion and thermal behaviour of MFGs/MFGM at pH 6.30.
Different acoustic powers generated by the 20 kHz and 40 kHz independently or synchronously working conditions, affected the interfacial properties and thermal behaviour of MFGs/MFGM samples. 20 kHz treatments led to a relatively even particle distribution in MFGs/MFGM compared to 40 kHz and 20 + 40 kHz treated MFGs/MFGM. Ultrasound treatment significantly resulted in the decrease of interfacial tension (π) in all MFGs/MFGM (p0.05). Three typical crystal forms, α-crystal, β-form and β'-form, were observed in control and ultrasonicated 5 min MFGs/MFGM, but α-crystal disappeared in all the 15 min treated MFGs/MFGM. Ultrasonic duration has a more profound effect on the increase of β'- crystal than the intensity. Ultrasonic treatments promoted the crystallisation of MFGs/MFGM fat at higher temperature but increased the melting temperature of MFGs/MFGM. Additionally, the 15 min treatments caused more pronounced changes in the intramolecular β-sheet, random coil, and α-helix structures compared to the 5 min treatments. 20 + 40 kHz/ 15 min treatment led to aggregated membrane proteins indicated by the confocal laser scanning microscopy (CLSM) images. All the MFGs/MFGM exhibited shear-thinning behaviour, except for the 40 kHz treated MFGs/MFGM, which displayed non-Newtonian behaviour at the lower shear rate.
The preliminary investigation on the effects of HMP incorporation on the MFGs/MFGM materials showed the enhanced absorbance at the Amide I and Amide II bands and altered fingerprint regions among all the MFGs/MFGM. Larger particle sizes ranging from 10 to 100 μm presented in the 0.30% HMP MFGs/MFGM, suggesting the formation of conjugates between HMP and milk proteins. These structural and compositional changes induced by HMP affected the physical stability and rheological properties of MFGs/MFGM. Notably, MFGs/MFGM with 0.30% HMP exhibited the poorest stability, a significant increase in apparent viscosity, and shear-thinning behavior throughout the analysis.
In summary, acidification, ultrasonic treatments, and HMP incorporation significantly impact the structural, compositional, and functional properties of MFGs/MFGM ingredients.
Description
Keywords
Milk fat globules/milk fat globule membrane , Acidified bovine milk , Ultrasonic treatment , High-methoxyl pectin , Physicochemical properties , Interfacial properties , Thermal properties
Citation
Sun, Y. 2024. Reconstruction of milk fat globules/membrane (MFGs/MFGM) and characterization of its physicochemical properties and techno-functionalities. PhD Thesis, University College Cork.