Ultrasonication retains more milk fat globule membrane proteins compared to equivalent shear-homogenization

Yaowei Liu,Sjef Boeren,Lina Zhang,Peng Zhou,Kasper Hettinga

doi:10.1016/j.ifset.2021.102703

Abstract

Ultrasonication, like common shear homogenization, can reduce the milk fat globule size and may change the milk fat globule membrane (MFGM). This work compared the effect of ultrasonication to equivalent shear homogenization on MFGM proteins and lipid-derived volatile components. Results showed that treating milk with ultrasound at 35 kJ/L would realize a similar size distribution of the milk fat globules as shear-homogenization at 20 MPa. Proteomics analysis revealed that in total 192 MFGM proteins were identified and quantified and a number of these proteins were lost after both treatments; however, more MFGM proteins remained after ultrasonication than after shear-homogenization. SDS-PAGE results showed that milk plasma proteins, and especially caseins, were absorbed on the milk fat globules after both treatments. In addition, the amount of the volatile free fatty acids increased after both treatments.Industrial relevance: Ultrasonication, as an innovative food processing technology, in comparison to traditional homogenization, was shown to equally efficiently decrease the MFG size, but lead to less damage to native MFGM proteins, which may be due to its longer homogenization time window. These results increased knowledge on the biochemical changes of milk fat globules after their size reduction and showed that ultrasonication could be used as a novel approach to improve dairy product quality.

Highlights

The lipids in milk are present in the form of milk fat globules (MFG), consisting of a triglyceride core, surrounded by a thin membrane, called the milk fat globule membrane (MFGM) consisting of an inner mono layer and an outer bilayer (Dewettinck et al, 2008)
Ultrasonication has been considered as an effective system for ho mogenizing MFG through cavitation effects, which refers to formation and violent collapse of bubbles (Ertugay & Sengül, 2004)
To find the appropriate ultrasonication treatment dosage that would have a similar homogenization effect compared with shear homogenization, we treated the milk at different treatment intensities and times (40 W and 60 W for 30, 60, 90, 120, and 180 s)

Summary

Introduction

The lipids in milk are present in the form of milk fat globules (MFG), consisting of a triglyceride core, surrounded by a thin membrane, called the milk fat globule membrane (MFGM) consisting of an inner mono layer and an outer bilayer (Dewettinck et al, 2008). MFGM contains polar lipids, cholesterol, and membrane-specific proteins, acts as an emulsifier for milk fat, and protect the MFG from enzymatic degradation and coalescence (Holzmüller & Kulozik, 2016; Zheng et al, 2020). Filtration of buttermilk, are the most common methods to isolate MFGM material. These isolation procedures will inevitably lead to a loss of native MFGM proteins (Holzmüller, Müller, Himbert, & Kulozik, 2016)

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