Bovine Milk Triacylglycerol Regioisomer Ratio Shows Remarkable Inter-Breed and Inter-Cow Variation

Abstract

Regioisomers (or positional isomers) of triacylglycerols (TAGs) of milk are known to show differential outcome in relation to human absorption. Quantitation of TAG regioisomers remains a big challenge due to the lack of facile chromatographic separation technique. The feasibility of using fragment ion intensity ratio to determine the ratio of co-eluting AAB/ABA-type regioisomer pairs was confirmed in this study. The ability of C30 stationary phase in resolving interfering TAG isomers was demonstrated for the first time. This allowed us to reveal the complexity of using fragment ion intensity to quantify 1,2-olein-3-palmitin (OOP), 1,3-olein-2-palmitin (OPO), 1,2-olein-3-stearin (OOS), and 1,3-olein-2-stearin (OSO) regioisomers in milk samples. A novel algorithm was proposed to consider the contribution of OPO/OOP and OSO/OOS double bond (DB)-isomers and to eliminate the interference of isobaric ions from other isomers, an aspect overlooked in previous studies. This liquid chromatography-mass spectrometry method that requires no pre-fractioning and a moderate chromatographic separation time of 36 min is simple and, thus, suitable for screening a large number of samples for genetic analysis of this trait. Preliminary results using a small cohort of animals showed that OPO/OOP ratio differs significantly between Jersey and Holstein cows, and a large variation was also observed across individual Holstein cows.

Advanced Tandem Mass Spectrometric Analysis of Complex Mixtures of Triacylglycerol Regioisomers: A Case Study of Bovine Milk Fat

“…The method was applied for analyzing the OPO/OOP and the OSO/OOS pairs using fragment ion intensity ratios. As a result, it provides structural information for targeted TAGs rather than comprehensive information on the regioisomer profile in bovine milk . They concluded that the regioisomer ratios are affected by both cow breed and individual cows, but our OPO and OSO ratios are comparable with the average results in their study, having the closest matching profile of the two regioisomer pairs in the milk fat of the Jersey cow breed.…”

“…For comparison of the bovine milk TAG regioisomer results, there are very limited studies that have taken into account the effects of isobaric fragment ion interference. Recently, Liu et al demonstrated the regioisomeric analysis of specific bovine milk TAGs emphasizing chromatographic separation of interfering isobaric TAGs species with C30 stationary phase column . The method was applied for analyzing the OPO/OOP and the OSO/OOS pairs using fragment ion intensity ratios.…”

“…It has been shown that cow breed can significantly influence the regioisomer ratios of certain TAGs in bovine milk. 34 While the amount of investigated TAG regioisomers in that study was limited to two pairs, it shows that there can potentially be substantial differences in the milk TAG regioisomer composition of different cow breeds. As bovine milk is a significant ingredient for food industry worldwide, deep characterization of the molecular structure will enhance our knowledge on its nutritional effects and show what factors potentially lead to differences in the regioisomer composition.…”

“…Bovine milk fat is considered to be one of the most complex natural mixtures of TAGs, containing a wide range of fatty acids of short to long chains and varying number of double bonds. , Although molecular species of TAGs in bovine milk have been widely reported by previous studies, , the regioisomeric composition remains still largely unknown, mainly due to the lack of comprehensive analytical methods. It has been shown that cow breed can significantly influence the regioisomer ratios of certain TAGs in bovine milk . While the amount of investigated TAG regioisomers in that study was limited to two pairs, it shows that there can potentially be substantial differences in the milk TAG regioisomer composition of different cow breeds.…”

Determination of 1,3-olein-2-palmitin (OPO) content in infant formula by liquid chromatography coupled mass spectrometry LC-MS/MS

“…Trên thế giới đã có nhiều phương pháp xác định hàm lượng OPO trong chất béo, trong thịt lợn, thịt bò và sữa, bằng nhiều kỹ thuật như sắc ký khí ion hóa ngọn lửa GC-FID [4][5], quang phổ cộng hưởng từ hạt nhân 13 C-NMR [6], sắc ký lỏng và sắc ký lỏng khối phổ [7][8][9]. Tuy nhiên, phương pháp GC-FID có quá trình xử lý mẫu phức tạp, tốn nhiều thời gian.…”