Chapter 10 - Milk as a Natural Product: Foreign Natural and Anthropogenic Organic Compounds in It

Abstract

Abstract Few researchers in the phytochemical sciences regard milk as a bioactive natural product. However, milk emanates entirely from living mammals and every carbon atom in milk stems directly or indirectly from plants, fungi, and bacteria with the exception of anthropogenic contaminants. In addition to the usual constituents of milk, lactogenesis or milk synthesis drags with it a substantial number of adventitious organic compounds, healthy, and appetizing or downright harmful and repulsive, acquired through diet, breath, and skin absorption. Animals and people alike are exposed to a large number of organic pollutants, pharmaceutical drugs, substances from wood combustion for cooking and heating, and many other sources related to human activities. These nonnatural products can reach pristine remote pastures carried by long range air circulation, posing new challenges to dairy cattle husbandry. Many of these compounds are carried over to milk passing through the animal in proportion to the lipid-to-water partition coefficients and to physicochemical features well defined by their molecular structure. Several compounds uptaken in blood get across the plasma–milk barrier by way of passive diffusion or aided by specific transmembrane transporters. Milk chemistry is also a complex biochemical subject. As a most nutritious medium, milk harbors numerous bacteria, fungi, and yeasts that modify deeply its natural chemistry through catabolism of existing compounds or introducing new ones. If pathogen infestation of milk continues to be a major problem, in part due to the formation of obnoxious exo and endotoxins and other products of their metabolism, the complex microcosm thriving in milk is also a source of opportunities for the dairy industry. Proper management and deep knowledge of the natural organic chemistry of milk and downstream dairy products can not only prevent product spoilage but also enhance its nutritional, nutraceutical, and taste qualities. This latter property is extensively being exploited to manufacture cultured creams, yogurts, spreads, and cheeses of ever growing sophistication, as are methods of analytical organic chemistry and quality control of milk feedstocks. In reviewing the literature of the past 25 years and up to mid-2016, this chapter emphasizes the natural product essence of milk as a biochemically living stuff of exceedingly complex and dynamic organic chemistry, subject to great variability considering the number of inputs from the outside of the mammal, internal processing of the ingested organic materials, microbial intervention in the digestive tract in healthy and diseased livestock, and the multifarious ripening of fermented dairy products that make them favorite foods for millions of people across the world.