Comparison of methylation methods for fatty acid analysis of milk fat

Food Chem. 2018 Sep 30:261:210-215. doi: 10.1016/j.foodchem.2018.04.053. Epub 2018 Apr 17.

Abstract

Three acid- and alkaline-catalysed transesterification methods were compared with the aim to validate a simple yet reliable protocol for fatty acid (FA) profiling of milk fat. While both the acid- and alkaline-catalysed methods were able to convert completely triglycerides and phospholipids into fatty acid methyl esters (FAMEs), the acid catalyst caused significant degradation of conjugated linoleic acid C18:2c9t11 at high temperature. Although a milder temperature can mitigate this negative impact, a long reaction time (2 h) is required to achieve full methylation. By contrast, despite being unable to methylate free fatty acids (FFA), the alkaline-catalysed transesterification yielded comparable results for all major FA due to the very low level of FFA in milk. The alkaline-catalysed methylation is benign for C18:2c9t11. We recommend here a simple one-step protocol based on 0.2 M methanolic KOH, a short reaction time (20 min) and a mild reaction temperature (50 °C) for milk FAME preparation.

Keywords: Fat; Fatty acids; Methylation; Milk.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Dietary Fats / analysis
  • Fatty Acids / analysis*
  • Fatty Acids, Nonesterified / analysis
  • Fatty Acids, Nonesterified / chemistry
  • Food Analysis / methods*
  • Linoleic Acids, Conjugated / analysis
  • Linoleic Acids, Conjugated / chemistry
  • Methylation
  • Milk / chemistry*
  • Phospholipids / chemistry
  • Triglycerides / chemistry

Substances

  • Dietary Fats
  • Fatty Acids
  • Fatty Acids, Nonesterified
  • Linoleic Acids, Conjugated
  • Phospholipids
  • Triglycerides