The surface properties of milk fat globules govern their interactions with the caseins: Role of homogenization and pH probed by AFM force spectroscopy

SUMMARYA method capable of determining the interfacial tension (γ) of individual emulsified liquid drops has been investigated and applied to a study of the surface properties of milk fat globules. Measurements on several organic liquids in bulk against water were made to validate and standardize the technique. With one exception, results agreed well with literature values, but the reproducibility of measurements was not as good as that of other, standard, methods. Measurements performed on small drops were affected by several factors and precision was not high.The influence of different milk treatments upon the interfacial tension of milk fat globules was studied. Agitation of milk had the effect of increasing γ while the effect was reversed upon allowing agitated milk to stand. Dilution of normal milk with water resulted in an increase in γ while acidification and alkalization produced a decrease. Pasteurization of raw milk caused a slight, non-significant decrease. Values of γ were low, 1–2 mN m-1, irrespective of the nature of the milk treatment and were an order of magnitude smaller than those obtained for interfaces of butter oil and milk protein solutions. The results support the concept of a 2-layer membrane and suggest that changes in γ follow mainly the adsorption/desorption of surface active components in the outer hydrophilic layer of the globule membrane. An inner, firmly bound lipophilic layer, resistant to many different milk treatments, appears to determine the overall low γ value under most conditions.

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Milk Fat Globule Membrane Proteome and Micronutrients in the Milk Lipid Fraction: Insights into Milk Bioactive Compounds

Dairy ◽

10.3390/dairy2020018 ◽

2021 ◽

Vol 2 (2) ◽

pp. 202-217

Author(s):

Michele Manoni ◽

Donata Cattaneo ◽

Sharon Mazzoleni ◽

Carlotta Giromini ◽

Antonella Baldi ◽

...

Keyword(s):

Milk Fat ◽

Lipid Fraction ◽

Value Added ◽

Milk Lipid ◽

Milk Fat Globule Membrane ◽

Fat Globules ◽

Milk Fat Globules ◽

Milk Fat Globule ◽

Fat Globule ◽

Value Added Products

Milk lipids are composed of milk fat globules (MFGs) surrounded by the milk fat globule membrane (MFGM). MFGM protects MFGs from coalescence and enzymatic degradation. The milk lipid fraction is a “natural solvent” for macronutrients such as phospholipids, proteins and cholesterol, and micronutrients such as minerals and vitamins. The research focused largely on the polar lipids of MFGM, given their wide bioactive properties. In this review we discussed (i) the composition of MFGM proteome and its variations among species and phases of lactation and (ii) the micronutrient content of human and cow’s milk lipid fraction. The major MFGM proteins are shared among species, but the molecular function and protein expression of MFGM proteins vary among species and phases of lactation. The main minerals in the milk lipid fraction are iron, zinc, copper and calcium, whereas the major vitamins are vitamin A, β-carotene, riboflavin and α-tocopherol. The update and the combination of this knowledge could lead to the exploitation of the MFGM proteome and the milk lipid fraction at nutritional, biological or technological levels. An example is the design of innovative and value-added products, such as MFGM-supplemented infant formulas.

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