Milk Powder Extraction: Optimization of Conditions for the Water-Soluble Metabolites by Proton Nuclear Magnetic Resonance (¹H-NMR)

Abstract

Milk is a favorable for humans due to its nutritional composition. Metabolites in milk relevant to human health have received increased attention. Proton nuclear magnetic resonance (¹H-NMR) is commonly used for water-soluble metabolites due to rapid data acquisition and excellent precision. Extraction to separate fats and proteins from the metabolites is necessary to obtain high quality spectra. In the present work, various extraction procedures were compared for ¹H-NMR. The mass of milk for extraction was also optimized. Overall, 2/1 (v/v) methanol/skim milk was selected to be the most efficient system. The best precision was obtained for 500 to 600 mg milk powder redissolved in 2 mL water and 0.5 mL skim milk for the subsequent extraction. This study provides a sample preparation protocol for milk metabolomics that may be appropriate for other samples.

KEYWORDS:

• Extraction
• metabolomics
• milk
• proton nuclear magnetic resonance (1H-NMR)

Additional information

Funding

This work was supported by MBIE NZ-China Grant: Integrated Tracing Technologies for Dairy Products (Grant number: UOOX1501) and the University of Otago PhD Scholarship.