Milk lipids characterization in relation to different heat treatments using lipidomics
Graphical abstract
Introduction
Milk is an important nutrient source in the human diet. One of the main components of milk solids, lipids account for 3%–5% of the total milk composition. Milk lipids profoundly impact the properties and quality of milk and are also important nutrients (Liu, Li, Pryce, & Rochfort, 2020b). Fat in milk exists in the form of fat globules. Triacylglycerols (TGs) are located in the core of the fat globules and account for more than 98% of the total milk fat (Liu, Li, Pryce, & Rochfort, 2020a). The TG core is wrapped in the milk fat globule membrane (MFGM) composed of phospholipids, glycolipids, and proteins (Gallier, Gragson, Jimenez-Flores, & Everett, 2010). Polar lipids in the fat globule membrane have a significant impact on human health (Kosmerl, Rocha-Mendoza, Ortega-Anaya, Jimenez-Flores, & Garcia-Cano, 2021), such as improving neurodevelopment, reducing the risk of cardiovascular diseases, and regulating cholesterol absorption (Silva et al., 2021, Snow et al., 2010). Lipids in milk are attracting increasing attention.
To extend milk storage time and ensure its safety, heat treatment has become a necessary step in commercial milk production (Li et al., 2021, Zhang et al., 2018). However, heat treatment leads to the deterioration of sensory quality (Oupadissakoon, Chambers, & Chambers, 2009) and changes in milk lipid composition (Jadhav, Annapure, & Deshmukh, 2021). Heat treatment causes casein and whey protein to bind to the MFGM surface through the disulfide interchange reaction, which causes structural changes in the MFGM (Sharma, Oey, & Everett, 2015). Moreover, heat treatment affects fat globule stability and lipid digestion (Lund, Nielsen, Nielsen, Ray, & Lund, 2021). Although pasteurization does not cause significant changes in the milk fatty acid (FA) composition, it significantly increases the levels of oxylipins derived from arachidonic acid and 18-carbon polyunsaturated fatty acids (PUFAs; linoleic acid and α-linolenic acid) (Pitino et al., 2019). In addition, studies on the volatile components of milk have shown that heat treatment leads to the formation of methyl ketones in milk, which impacts milk flavor (Reis et al., 2020). The influence of heat treatment on milk FAs has been extensively studied, but the biological function of lipids and their potential nutritional value are usually related to specific lipid species or even the stereo-structures of lipid molecules (Contarini & Povolo, 2013). Therefore, it is necessary to comprehensively characterize lipid changes caused by heat treatment at the molecular level.
The development of high-resolution mass spectrometry has greatly promoted qualitative and quantitative studies of milk lipids (Liu et al., 2020b). Several reports have proven the feasibility of using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) for non-targeted milk lipidomics, including identifying 411 species of lipids in human milk (Zhao et al., 2021) and characterizing human milk phospholipid profiles at different lactation stages (Song et al., 2021). In addition, differences in lipid composition between infant formula and human milk were discovered using a similar method (X. Zhang et al., 2021). However, there is still a lack of research using this technique to explore the relationship between heat treatment and lipid changes in milk.
In this study, we used ultra-high performance (UHP) LC-Q-TOF-MS/MS to comprehensively characterize the lipid composition of milk after processing using different heat treatments. Our results revealed changes in milk lipids specific to the heat treatment and provide a reference for identifying the thermal-processing degree of milk.
Section snippets
Chemicals and reagents
Methyl tert-butyl ether (MTBE), methanol (MeOH), and dichloromethane (DCM) (all HPLC grade) for lipid extraction were purchased from Macklin Biochemical (Shanghai, China). Isopropanol (IPA) and acetonitrile (ACN) (both LC-MS grade) were purchased from Fisher Scientific (Waltham, MA, USA). Decanoic acid(d10) standard was obtained from Macklin Biochemical (Shanghai, China). C15 Ceramide-d7 Standard and SPLASH® LIPIDOMIX® Mass Spec Standard were obtained from Avanti Polar Lipids (Alabaster, AL,
Lipids identification
A total of 29 lipid classes and 788 lipid species were identified. The qualitative and quantitative lipid results are shown in Tables S3 and S4, respectively. Among the 29 identified lipid classes, glyceride (GL) and free fatty acids (FFAs) were the main lipid components in milk, accounting for 98.2%–98.4% of the total lipids (Table 1). Oxidized lipids (0.53%–0.96%) were the second most abundant lipids in milk, including OxTG, OxFFA, OxPC, OxPE, and OxPI. In addition, the composition of polar
Conclusions
In summary, a comprehensive lipidomics approach was used to study variations in the lipid profiles associated with different heat treatments of milk. A total of 29 types of lipids and 788 different lipid species were identified and quantified. Heat treatment led to a significant increase in the hydrolysis of milk lipids. ESL treatment led to the highest level of hydrolysis of TGs, and UHT treatment led to the highest hydrolysis of GPs. With the enhancement of heat treatment, the oxidization of
CRediT authorship contribution statement
Hongda Zhang: Conceptualization, Methodology, Investigation, Data curation, Visualization, Writing – original draft. Yanyang Xu: Investigation, Methodology, Data curation. Chengxiang Zhao: Investigation, Methodology, Data curation. Yi Xue: Methodology, Formal analysis, Writing – review & editing. Dongfei Tan: Methodology, Formal analysis, Writing – review & editing. Shaolei Wang: Resources, Methodology. Man Jia: Resources, Methodology. Huaxing Wu: Resources. Aijin Ma: Conceptualization, Writing
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors thank New Hope Dairy Co., Ltd. (Sichuan, China) for providing the processed milk samples.
Funding
The project was supported by the Huhhot Science & Technology Plan, National Dairy Innovation Center [grant number 2021-10].
References (51)
- et al.
Lipid peroxidation generates biologically active phospholipids including oxidatively N-modified phospholipids
Chemistry and Physics of Lipids
(2014) - et al.
Advances in Our Understanding of Oxylipins Derived from Dietary PUFAs
Advances in Nutrition
(2015) - et al.
The role of heat treatment in light oxidation of fluid milk
Journal of Dairy Science
(2020) - et al.
Fat globules selected from whole milk according to their size: Different compositions and structure of the biomembrane, revealing sphingomyelin-rich domains
Food Chemistry
(2011) - et al.
Lipid extraction by methyl-tert-butyl ether for high-throughput lipidomics
Journal of lipid research
(2008) - et al.
Nanomolar concentrations of lysophosphatidylcholine recruit monocytes and induce pro-inflammatory cytokine production in macrophages
Biochemical and Biophysical Research Communications
(2008) - et al.
Seasonal variation in fatty acid and triacylglycerol composition of bovine milk fat
Journal of Dairy Science
(2021) - et al.
Interfacial properties and transmission electron microscopy revealing damage to the milk fat globule system after pulsed electric field treatment
Food Hydrocolloids
(2015) - et al.
Short communication: Decrease of lipid profiles in cow milk by ultra-high-temperature treatment but not by pasteurization
Journal of Dairy Science
(2020) - et al.
Lipid composition and structural characteristics of bovine, caprine and human milk fat globules
International Dairy Journal
(2016)
Seasonal variation in the positional distribution of fatty acids in bovine milk fat
Journal of Dairy Science
A metabolomics approach to characterize raw, pasteurized, and ultra-high temperature milk using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry and multivariate data analysis
Journal of Dairy Science
Lipid compositional changes and oxidation status of ultra-high temperature treated Milk
Lipids in Health and Disease
Generation and Biological Activities of Oxidized Phospholipids
Antioxidants & Redox Signaling
Functional Lipids in Autoimmune Inflammatory Diseases
International Journal of Molecular Sciences
Integral Stereoselectivity of Lipase Based on the Chromatographic Resolution of Enantiomeric/Regioisomeric Diacylglycerols
Journal of Agricultural and Food Chemistry
Phospholipids in Milk Fat: Composition, Biological and Technological Significance, and Analytical Strategies
International Journal of Molecular Sciences
Heat-induced changes in the sensory properties of milk
International Dairy Journal
Plasmalogens, platelet-activating factor and beyond - Ether lipids in signaling and neurodegeneration
Neurobiology of Disease
Using Confocal Laser Scanning Microscopy To Probe the Milk Fat Globule Membrane and Associated Proteins
Journal of Agricultural and Food Chemistry
Milk Fatty Acid Profile of Holstein Cows When Changed from a Mixed System to a Confinement System or Mixed System with Overnight Grazing
International Journal of Food Science
Milk phospholipid antioxidant activity and digestibility: Kinetics of fatty acids and choline release
Journal of Functional Foods
Non-thermal Technologies for Food Processing
Frontiers Nutrition
UHPLC-Q-Orbitrap HRMS-based quantitative lipidomics reveals the chemical changes of phospholipids during thermal processing methods of Tan sheep meat
Food Chemistry
Cited by (10)
Promising bioactivities of postbiotics: A comprehensive review
2023, Journal of Agriculture and Food ResearchLipidomics in milk: recent advances and developments
2023, Current Opinion in Food Science