Oleic Acid in Milk of Different Mammalian Species

Milk from different mammal species, being a biological fluid, varies considerably in many of its constituents. Fat content of milk is the nutrient showing the most variation in its percentage. In fact, milk fat is one of the most complex of all common fats, composed of about 98% triglycerides; other milk lipids (as a percentage of the total milk fat) include diacylglycerides (0.25-0.48%), monoacylglycerides (0.02-0.04%), phospholipids (0.6-1.0%), cholesterol (0.2-0.4%), glycolipids (0.006%) and free fatty acids in milk (0.1-0.4%). Milk fat contains many fatty acids, mainly saturated but also monounsaturated and polyunsaturated. Several factors, many of which are interactive, are known to cause variation in milk fatty acid composition. These include stage of lactation, seasonal variations, feeding and animal genetic. Milk fatty acid composition has been frequently investigated because of its implications for human health; due to the relationship between high-fat diets and heart diseases, consumer interest in milk fat content and also in fatty acid composition of foods has grown in the recent years. Oleic acid (C18:1cis9), a monounsaturated fatty acid, has been deeply studied because of its possible beneficial effects on human health, normally associated with a reduction of serum cholesterol and also of plasma cholesterol levels. Scientific evidence and nutritional guidelines recommend a reduction in total fat intake, and particularly of saturated fatty acids, which are associated with an increased risk of obesity, hypercholesterolemia and some cancers. In mammalian species, milk fat has a double origin: circulating fatty acids are transported in lipoproteins, other fatty acids are synthesised in the udder. The fatty acid composition of milk fat is of interest because it affects both the texture and the flavour of dairy products. Milk fat in ruminant species is characterized by an higher content of saturated fatty acids, while fatty acid composition in mare’s milk and donkey’s milk shows interesting percentages of essential fatty acids.