Actual Ratio of Triacylglycerol Positional Isomers in Milk and Cheese

Abstract

Actual ratios of triacylglycerol (TAG) positional isomers in human, rat, and cow milk fat and cow, buffalo, goat, and sheep cheese fat were analyzed using HPLC–UV–atmospheric pressure chemical ionization–MS/MS system equipped with an octacosyl silylation column or polymeric ODS column. We substituted cheese fats for milk fats in parts of our study because milks from ruminants, with the exception of cows, are difficult to get in Japan. The actual ratio of β–PPC (the TAG consisting of two palmitic acids (P) and one capric acid (C), with the palmitic acid located at the β position) and β–PCP in human milk was different from those in ruminants, with more than half of the medium-chain fatty acids located at the β position even though other fats possessed it mainly at the α position. Palmitic acid was mainly located at the β position for human milk and rat milk; however, the location in ruminant cheese fat was mainly at the α position. The location of fatty acids is thought to be very important for infant nutrition. Particularly, the location of palmitic acid in case of human milk and of medium-chain fatty acids in case of ruminant milk was very characteristic and is considered to be very important to the fatty acids in milk fat.