Abstract: Gas chromatography-mass spectrometry (GC-MS) and microscopic observation were used to analyze the relative contents of major functional unsaturated fatty acids, physicochemical properties and microstructure of fat globules in breast milk and goat milk from different lactation periods, aiming at providing a theoretical basis for the study of breast milk lipids and the development of infant formula based on goat milk. The results showed that the fat contents of colostrum, transitional and mature breast milk were (26.7 ± 3.6), (33.7 ± 4.6) and (41.0 ± 6.8) g/L, respectively, increasing significantly with the prolongation of lactation (P < 0.05). The relative content of fat in goat milk ((42.1 ± 4.3) g/L) was significantly higher than in human colostrum and transitional milk (P < 0.05). However, the major functional fatty acids were significantly more abundant in breast milk than in goat milk (P < 0.05). Notably, the content of linoleic acid (LA) (the lowest in the transitional period, 19.76%) was significantly higher than that of goat milk (4.43%) (P < 0.05). In terms of physical properties, breast milk fat globules (MFG) had the maximum average particle size of (5.63 ± 0.51) μm and the minimum zeta potential of (?5.72 ± 0.21) mV, while the average particle size and potential of goat milk MFG were (3.63 ± 0.31) μm and (?13.69 ± 0.27) mV, respectively. Furthermore, MFG particle size and potential were significantly correlated with fat content (P < 0.05). The major functional fatty acids and MFG physical properties in breast milk at different lactation stages were different, which were significantly different from those in goat milk. The results of this experiment can be useful for further study of breast milk and goat milk products.

Key words: breast milk, goat milk, functional fatty acids, fat globules, microstructure