European Journal of Nutrition

, Volume 44, Issue 7, pp 436–444

The dispersion state of milk fat influences triglyceride metabolism in the rat

A 13CO2 breath test study
ORIGINAL CONTRIBUTION

DOI: 10.1007/s00394-005-0551-1

Cite this article as:
Michalski, MC., Briard, V., Desage, M. et al. Eur J Nutr (2005) 44: 436. doi:10.1007/s00394-005-0551-1
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Summary

Background

Milk fat, which has different structures in the various dairy products, is a major and controversial lipid source in the Western diet. However, information about the digestion fate of milk fat depending on its supramolecular structure for a given composition is scarce.

Aim of the study

In this study, 13CO2 breath tests were performed with fasted rats force–fed different dairy preparations of similar composition but differing in fat suprastructure in order to highlight differences of general lipid metabolism.

Methods

Each preparation consisted of a NaCl solution, anhydrous milk fat labelled with a 13C mixed triacylglycerol, casein (as native phosphocaseinate powder with some lactose), and dipalmitoylphosphatidylcholine. Milk fat was either fed (i) unemulsified consecutively to the aqueous phase, or emulsified as (ii) coarse droplets of ∼10 µm covered mainly with the phospholipid, or (iii–iv) fine droplets of ∼1 µm covered mainly with casein, force–fed either in the liquid state or in a semi–crystallized state. 13C abundance in expired air samples was measured by isotope ratio mass spectrometry; results were expressed as 13C enrichment and were submitted to an ANOVA analysis.

Results

The 13CO2 excretion curves of the unemulsified preparation and the coarse emulsion were similar and presented a sharp peak, both significantly different from the fine emulsion curves characterized by a nearly linear cumulative recovery. The crystalline state of the fine emulsion droplets and the viscosity of these emulsions did not affect significantly their excretion curves. The lipid metabolization (indicated by the 13C recovery) was significantly slower for the fine droplets coated with casein than for the large droplets coated with the phospholipid and the unemulsified fat. For the latter, a single 13C peak rapidly appeared, while for small droplets coated with caseins, 13C excretion was continuous up to 6 h.

Conclusions

Global lipid metabolism based on oxidation to CO2 was decreased with smaller compared to larger emulsified milk fat particles with different coatings. These data support the concept that dairy products with different fat suprastructures are digested and metabolized differently.

Key words

13C MTG breath test digestion emulsion droplet size interface milk fat 

Abbreviations

CEP

coarse emulsion whose fat droplets are coated with phospholipid (dipalmitoyl–phosphatidylcholine)

δ

13C abundance of the sample

δ0

baseline 13C abundance

d32

Sauter volume–surface average diameter

d43

volume averaged diameter

FEC

fine emulsion whose fat droplets are coated with casein

FFP

preparation consisting of free fat plus aqueous–proteinaceous phase force-fed consecutively

MTG

mixed triacylglycerol

S

specific surface area

Slope

slope of the cumulative 13CO2 excretion curve (from measured values)

St–[1–13C]Oct–St

2–octanoyl [1–13C]–1.3 distearoyl glycerol

t0.5

time of half 13CO2 elimination compared to the maximum for free fat at 360 min (from measured values)

Copyright information

© Steinkopff-Verlag 2005

Authors and Affiliations

  • M.-C. Michalski
    • 1
    • 2
  • V. Briard
    • 1
  • M. Desage
    • 3
  • A. Geloen
    • 4
  1. 1.Sciences et Technologie du Lait et de l’ŒufUMR INRARennesFrance
  2. 2.Institut Multidisciplinaire de Biochimie des Lipides INSA—Louis Pasteur BuildingVilleurbanneFrance
  3. 3.Centre de Recherche en Nutrition Humaine de LyonFaculté de Médecine René Laënnec Université Claude Bernard—Lyon ILyonFrance
  4. 4.Physiopathologie des Lipides et MembranesUMR 585 INSERM/INSAVilleurbanneFrance

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