Quantitative Analysis of Lactone Enantiomers in Butter and Margarine through the Combination of Solvent Extraction and Enantioselective Gas Chromatography-Mass Spectrometry.

We quantified the enantiomeric distributions of δ- and γ-lactones in butter, fermented butter, and margarine through the combination of solvent extraction and enantioselective gas chromatography-mass spectrometry. The main lactones in butter and fermented butter comprised (R)-δ-decalactone, (R)-δ-dodecalactone, (R)-δ-tetradecalactone, (R)-δ-hexadecalactone, and (R)-γ-dodecalactone. In contrast, margarine samples consisted of only δ-decalactone and δ-dodecalactone in racemic forms, indicating that synthetic aroma chemicals were added to margarine. After heat treatment, 13 types of lactones were detected in butter and fermented butter. In heated butter and fermented butter, major δ-lactones in the (R)-form were abundant, but only δ-octalactone in the (S)-form was detected. In contrast, γ-dodecalactone (main γ-lactone in the heated samples) was abundant in the (R)-form, whereas other γ-lactones were detected in the racemic form. These results suggested that the major lactones in dairy products are in the (R)-form. Furthermore, the heat treatment affected the enantiomeric distribution of lactones in butter and fermented butter.

Effects of Heat Treatment on Lactone Content of Butter and Margarine.

The lactone content of butter, fermented butter, and margarine was compared using gas chromatography-mass spectrometry. The main lactones in butters and fermented butters consisted of δ-decalactone, δ-dodecalactone, δ-tetradecalactone, δ-hexadecalactone, and γ-dodecalactone. In contrast, the main lactones in margarines were δ-decalactone and δ-dodecalactone. The total lactone content in butters and fermented butters increased by approximately two-fold upon heat treatment, whereas, heat treatment did not affect the lactone content in margarine. The changes in lactone content caused by heat treatment were greater in fermented butters than in butters. These findings suggested that the fermentation process could increase lactone or lactone precursor content in butter.

Analysis of hydroxy triacylglycerol as a lactone precursor in milk fat using liquid chromatography electrospray ionization tandem mass spectrometry.

Heating milk fat leads to lactone formation. Hydroxy fatty acids, esterified in triacylglycerol (TAG), are likely precursors of lactones in milk fat, but respective hydroxy TAG isomers have not been directly detected for several decades. In this study, we separated hydroxy TAG isomers-1,2-dipalmitoyl-3-(5-hydroxy decanoyl)-rac-glycerol (PP(C10-5OH)-TAG), 1,2-dipalmitoyl-3-(5-hydroxy dodecanoyl)-rac-glycerol (PP(C12-5OH)-TAG), 1,2-dipalmitoyl-3-(5-hydroxy tetradecanoyl)-rac-glycerol (PP(C14-5OH)-TAG), and 1,2-dipalmitoyl-3-(4-hydroxy dodecanoyl)-rac-glycerol-by using liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) with an octacocyl silylation column. This method revealed the presence of PP(C10-5OH)-TAG, PP(C12-5OH)-TAG, and PP(C14-5OH)-TAG in butter oil, whereas no hydroxy TAG isomers were detected in heat-treated butter oil. Furthermore, a heating test of hydroxy TAG standards showed a decrease in hydroxy TAG levels and an increase in the corresponding lactone levels. These changes were stimulated by adding a small amount of water. This is the first reported analysis of respective hydroxy TAG isomers in milk fat using LC-ESI-MS/MS.

Simple Quantification of Lactones in Milk Fat by Solvent Extraction Using Gas Chromatography-Mass Spectrometry.

The analysis of lactones as an indicator of milk quality is important in food manufacturing. However, the extraction of lactones requires sensitive conditions due to their volatility. In this study, the parameters for resolution of lactone standards were evaluated by gas chromatography-electron ionization/mass spectrometry (GC-EI/MS) to develop a rapid and simple method for the quantification and compositional analysis of lactones in edible fats, especially milk fat. Fourteen lactone standards consisting of 6-16 carbon atoms were analyzed and their correction factors (CFs) were obtained by using δ-undecalactone as an internal standard. The CFs of the lactone standards followed the same trend for δ-lactones and γ-lactones. Three volume equivalents of organic solvent per unit sample yielded the best recovery in the lactone analysis. Notably, 91-114% lactone recovery for the standards was achieved with methanol as the extractant. This method was also applicable to other fat samples, such as virgin coconut oil that is thought to contain large amounts of lactones. The recovery of lactones from virgin coconut oil was in the range of 87-104%, indicating that the developed method is also applicable to solid or semi-solid fat samples. The lactone content of butter oil, coconut oil, and butter samples was calculated by using the obtained CFs and the results were in good agreement with those of previous reports. Consequently, the GC-EI/MS method developed in this study is deemed applicable for the quantification of lactones in fat samples.