Lactose if One of the Major Components

Lactose if one of the major components of milk, and plays a crucial role in human development. This paper will examine the structure, function, physical properties, chemical properties, reactions, and everyday uses of lactose. In addition, a discussion of the common issue of lactose intolerance in humans is included.

A natural sugar found in milk, lactose is likely one of the most commonly identifiable of all milk ingredients (except perhaps calcium). Lactose makes up to 4.8 to 5.2% of milk, and 70% of the whey solids in milk.

Other carbohydrates in milk are present in small amounts, including glucose, galactose, and oligosaccharides. Milk also contains a number of other components, including water, milk lipids (which make up products like butter), and milk proteins like caseans and whey proteins (which are predominantly present in milk solids like cheese), milk enzymes (including lipoprotein lipase, plasmin, and alkaline phosphatase), and vitamins (B1 - thiamine, B2 - riboflavin, B6 - pyridoxine, B12 - cyanocobalamin, niacin, pantothenic acid), All 22 minerals essential to the human diet are found in milk, including sodium, chloride, potassium, calcium, magnesium, iron, nickel, manganese, zinc, copper, and even silicon and tin (University of Guelph).

Lactose is not found within plant sources, and is less sweet than many other sugars, including sucrose. Lactose is only found within milk, which is produced by lactating mammals, including humans, for the nourishment of their offspring. Milk is produced within animal mammary glands (Thelwall), and is the primary carbohydrate within milk in most animal species (Hurley).

In Western society, lactose (within milk) is used within a wide variety of milk products. Cheeses, cottage cheese, sour cream, and yogurts are milk products. In addition, milk is used in a wide variety of other food products, including breads, pizzas, ice cream products, and even cereals (Martens). The use of lactose as a fermentation product is an important component of the use of lactose in food products. Lactic acid bacteria make lactic acid from lactose, which acts as the basis of many fermented dairy products, such as sour cream and yoghurt (University of Guelph).

The souring of milk comes from a chemical reaction that occurs to the lactose molecule that is closely related to the fermentation process noted earlier. In common experience, soured milk tastes less sweet than fresh milk, reflecting the breakdown of lactose. When milk sours, lactose within the milk is converted to lactic acid by bacteria in the milk, thus reducing the sweetness of milk, and creating the off-putting acidic odor and taste that characterize lactic acid (Thelwall).

Lactose is a relatively insoluble molecule (University of Guelph). As such, this insolubility can often be a problem within the production and storage of many milk products including ice cream.

In structure, lactose is a white crystalline disaccharide that is comprised of two sugars that are bound together: glucose and galactose. Glucose and galactose are monosaccharides. Lactose has the same chemical formula as sucrose and maltose (C12H22O11). However, lactose differs from sucrose and maltose in structure. When hydrolyzed, lactose yields D-glucose and D-galactose. This hydrolysis is catalyzed by lactase within the digestive tract (Miller). Thy hydrolysis of lactose results in increased sweetness, and a depression of the freezing point of milk (University of Guelph).

Lactose synthesis requires to glucoses for each lactose molecule. The synthesis of lactose is dependent upon the levels of glucose in the blood. One glucose molecule is converted to UDP-glucose, then UDP-galactose by the action of an epimerase enzyme. The other glucose molecule is not modified within the glucose pathway. The synthesis of lactose occurs within the Golgi apparatus through a glucose transporter named GLUT 1. This glucose transporter is only present in mammary epithelial cells. Lactose synthesis is one way, and lactose is not hydrolyzed back into glucose and galactose (Hurley).

The molecule lactose is crystalline in form within nature, and within milk. Lactose crystallization takes place in an alpha form that commonly takes a tomahawk shape (University of Guelph).