Fractionation and characterisation of hard milk fat crystals using atomic force microscopy

Damien A Sebben; Nan Gao; Graeme Gillies; David A Beattie; Marta Krasowska

doi:10.1016/j.foodchem.2018.11.136

Fractionation and characterisation of hard milk fat crystals using atomic force microscopy

Food Chem. 2019 May 1:279:98-104. doi: 10.1016/j.foodchem.2018.11.136. Epub 2018 Dec 5.

Authors

Damien A Sebben¹, Nan Gao², Graeme Gillies³, David A Beattie⁴, Marta Krasowska⁵

Affiliations

¹ Future Industries Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia. Electronic address: Damien.Sebben@unisa.edu.au.
² Future Industries Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia.
³ Fonterra Research and Development Centre, Dairy Farm Road, Fitzherbert, Palmerston North 4442, New Zealand.
⁴ Future Industries Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia; School of Information Technology & Mathematical Sciences, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia.
⁵ Future Industries Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia; School of Information Technology & Mathematical Sciences, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia. Electronic address: Marta.Krasowska@unisa.edu.au.

PMID: 30611517
DOI: 10.1016/j.foodchem.2018.11.136

Abstract

The hard milk fat (HMF) fraction of milk fat was isolated via dry, thermal fractionation, followed by a solvent washing process. The resulting HMF crystals were visibly free of entrapped liquid fat, and subsequently characterised by thermal analysis, X-ray diffraction, and electron microscopy. The HMF crystals were found to be mostly β' and β'₂ crystalline structures, with a lamellar thickness of 42.7-44.1 Å. Additionally, crystal size was determined to be ≥1 μm in length and 0.4-1 μm in width. Atomic force microscopy (AFM) was used to further characterise the HMF crystals. AFM enabled 3D mapping and visualisation of crystal layering, as well as simple determination of layer thickness (∼4.2 ± 0.8 nm); a value in close agreement with the results obtained via X-ray analysis. The AFM characterisation approach provides a simple method of characterising HMF crystals, without suffering the limitations of other widely used techniques.

Keywords: Atomic force microscopy; Fat crystals; Fractionation; Hard milk fat.

MeSH terms

Animals
Calorimetry, Differential Scanning
Crystallization
Fats / chemistry*
Microscopy, Atomic Force*
Milk / chemistry
Milk / metabolism*

Substances

Fats