Ling-Zhi Cheong

Human Milk Fat Globules from Different Stages of Lactation: A Lipid Composition Analysis and Microstructure Characterization

The physicochemical properties of human milk fat globules (MFG) at different lactation stages from Danish mothers and the microstructure changes of MFG membrane (MFGM) at varied temperatures were investigated, and the relationship between chemical composition and the microstructure of MFGM was elucidated. The fat content in MFG was found to be significantly increased as lactation progressed, and colostrum MFG had the largest mean diameter of 5.75 ± 0.81 μm and the lowest ζ potential of -5.60 ± 0.12 mV. Chemical composition analyses of MFG revealed the following: (i) Colostrum milk fat constituted higher content in PUFAs (ω-6, and long-chain ω-6 and ω-3) than transitional and mature milk fats, with the corresponding lower content of SFA in its sn-2 position. (ii) The content of polar lipids among total lipids varied during lactation course (maximized at transitional stage); however, in terms of subclasses of polar lipids, no significant change of the relative content of sphingomyelin was observed, while the content of phosphatidycholine in mature milk was higher than that in colostrum and transitional milk. (iii) Inspection of fatty acid composition in phospholipids from different lactation milk revealed no remarkable and regular changes could be generalized; and no obvious difference of the morphologies of MFGM at different lactation stages can be visualized. An investigation of the microstructure change of MFGM vs temperature demonstrated that the segregated domains became larger as temperature decreased to 4 °C, while it became smaller when increased to 37 °C. This phenomenon indicated that, in addition to sphingimyelin and cholesterol, phospholipids might also contribute to increasing the segregated domains at lower temperature, while, at elevated temperature, these domains could be diminished, most likely due to a restructuring or distributing of sphingimyelin and cholesterol.

Lipid Composition Analysis of Milk Fats from Different Mammalian Species: Potential for Use as Human Milk Fat Substitutes

The lipid compositions of commercial milks from cow, buffalo, donkey, sheep, and camel were compared with that of human milk fat (HMF) based on total and sn-2 fatty acid, triacylglycerol (TAG), phospholipid, and phospholipid fatty acid compositions and melting and crystallization profiles, and their degrees of similarity were digitized and differentiated by an evaluation model. The results showed that these milk fats had high degrees of similarity to HMF in total fatty acid composition. However, the degrees of similarity in other chemical aspects were low, indicating that these milk fats did not meet the requirements of human milk fat substitutes (HMFSs). However, an economically feasible solution to make these milks useful as raw materials for infant formula production could be to modify these fats, and a possible method is blending of polyunsaturated fatty acids (PUFA) and 1,3-dioleoyl-2-palmitoylglycerol (OPO) enriched fats and minor lipids based on the corresponding chemical compositions of HMF.

Model for Human Milk Fat Substitute Evaluation Based on Triacylglycerol Composition Profile

Being the dominant components in human milk fat (HMF), triacylglycerol (TAG) composition might be the best approximation index to represent the composing characteristics of HMF. In this study, TAG composition of HMF from different lactation stages was analyzed by RP-HPLC-APCI-MS, and the establishment of a model for the precise evaluation of human milk fat substitutes (HMFSs) based on TAG composition was indirectly realized by employment of fatty acid composition and distribution and polyunsaturated fatty acid (PUFA) and TAG compositions. The model was verified by the selected fats and oils with specific chemical compositions, and the results revealed the degrees of similarity of these fats and oils in different evaluation aspects reflected their differences in corresponding chemical composition with HMF. The newly established evaluation model with TAG composition as a comparison base could provide a more accurate method to evaluate HMFSs and might have some inspirations for HMFS production in the future.

Composition and microstructure of colostrum and mature bovine milk fat globule membrane

The microstructures of colostrum and mature bovine milk fat globule membrane (MFGM) were investigated using confocal laser scanning microscopy (CLSM) at different temperatures, and the relationships between microstructure variations and the chemical compositions of the MFGM were also examined. Using a fluorophore-labeled phospholipid probe, we found that non-fluorescent domains on the MFGM were positively correlated with the amount of sphingomyelin at both room (20 °C) and physiological (37 °C) temperatures. However, at the storage temperature (4 °C), there were more non-fluorescent domains on the MFGM. These results indicate that the heterogeneities in the MFGM are most likely to be the result of the lateral segregation of sphingomyelin at the room and physiological temperatures, and at the storage temperature, phospholipids with saturated fatty acids affect the formation of these domains.

Oxidative Stability of Enzymatically Processed Oils and Fats

Publisher Summary Fats and oils with modified functional and nutritional properties are in high demand in the food industry. The physical characteristics of fats and oils—for instance, those related to their melting and crystallization profiles—are important for food technologists to consider because nutritionists and consumers display great interest in their nutritional properties, based on their composition. The fats and oils industry has extensively used chemical interesterification to alter the physical and/or nutritional properties of fats and oils. However, the random end products of chemical interesterification cannot meet the demand for lipids with specific structures and compositions. The enzymatic process, on the other hand, requires mild reaction temperature and pressure, which is vital for handling unsaturated Fatty Acids (FAs), and has some other advantages as well. Therefore, the enzymatic modification of fats and oils has been a popular topic for the past few decades. However, information on the oxidative stability of such products remains limited. This chapter reviews the newest developments regarding the oxidative stability of enzymatically processed fats and oils. Many researchers have noted that the reduced oxidative stability of fats and oils produced by enzyme-involving steps presents a disadvantage. Many explanations exist for the low oxidative stability of these products. One of them is that a change in lipid structure affects stability by increasing or decreasing the exposure of unsaturated FAs to oxygen as well as the oxygen solubility or diffusivity of sensitive FAs. Moreover, structural change may alter the state of metal ions in the system.

SURFACE ACTIVE LIPIDS AS ENCAPSULATION AGENTS AND DELIVERY VEHICLES

Surface active lipids, such as partial acylglycerols, phospholipids, and glycolipids, are amphiphilic molecules that lower either the surface tension of the medium in which they are dissolved or the interfacial tension between phases at which they are adsorbed. Due to their amphiphilicity, surface active lipids are able to self-assemble into various unique supramolecular structures ranging from micro- to nanoscales. These unique supramolecular structures are found to have enhanced physical properties ranging from increased gelation capability, guest molecules loading capacity, and in-vivo stability to targeted delivery and molecular recognition. Thus, surface active lipids have garnered huge interest as encapsulation agents and delivery vehicles in various industries including food, pharmaceutical, and cosmetics. Work has also been directed toward synthesis of novel compounds and structural modification of existing surface active lipids. This chapter presents a review on current state-of-the art design, synthesis, and purification of surface active lipids—partial acylglycerols, phospholipids, glycolipids, aminolipids and lipopeptides, phytosterol surfactant, and antioxidant esters and elucidates physical properties of such lipids, including self-assembling and formation of various supramolecular structures. It also discusses some potential applications of the surface active lipids.