Free from lactose

Occurrence of lactose

In mammalian milk as well as in dairy products, lactose makes up almost all of the carbohydrates. The amount of lactose in dairy products varies due to the manufacturing process. During cheese production, some of the lactose is separated with the whey and further broken down by ripening. Fresh cheeses therefore have a lactose content of more than 2 % and longer matured hard cheeses often have less than 0.1 % lactose.

Cow's milk contains up to 47 g/l lactose. It is obtained from sweet or sour whey, which is produced in large quantities as a by-product of cheese production. By heating, ultrafiltration and ion exchange, the whey is freed from lipids, proteins and minerals and concentrated in a vacuum. The lactose then crystallises from the concentrated solution.

Lactose intolerance - symptoms

People with lactose intolerance cannot tolerate milk and dairy products, or tolerate them poorly. The reason for this is an enzyme deficiency that prevents the absorption of lactose. This is the so-called double sugar (disaccharide), which cannot be absorbed by the mucous membrane of the small intestine, because it must first be broken down into the individual sugars (galactose and glucose). This requires the enzyme lactase, which is normally produced in the mucous cells of the small intestine. However, people with an intolerance cannot produce any or only a little of it, which is why the undesirable reactions occur. 

The following symptoms typically occur in lactose intolerance as soon as an individually intolerable amount of lactose ends up in the intestine:

  • bloated belly
  • feeling of fullness
  • intestinal wind
  • loud bowel sounds
  • abdominal pain
  • nausea, rarely with vomiting
  • diarrhea

The flatulence and abdominal pain are caused by the gases produced by the bacteria in the large intestine when they break down the undigested milk sugar. Other waste products that are produced in the process - namely lactic and fatty acids - have a "water-pulling" effect. As a result, more fluid flows into the intestine and causes diarrhoea.

Paradoxically, lactose intolerance can also lead to constipation. This is when the bacterial decomposition of lactose predominantly produces methane. This gas slows down intestinal activity and thus triggers constipation.

Important: If you are lactose intolerant, you should make sure that you get enough calcium to prevent osteoporosis or calcium deficiency. A regular check of the calcium level at the doctor's can provide information and an undersupply can be avoided.   


Characteristics of lactose

Lactose is a crystalline, colourless substance with a sweet taste; depending on the concentration, its sweetening power is between 25 and 60 % of the power of sucrose. In its anhydrous form, lactose is hygroscopic; from the aqueous solution, the more stable α-form crystallises out as a monohydrate. Lactose is less soluble in water than other sugars, such as maltose. The water solubility of the α- and β-forms differs considerably (5 and 45 g/100 g at 0 °C, respectively). Lactose is optically active and is one of the reducing sugars.

The individual components of lactose, galactose and glucose, are linked to each other via a β-1,4-glycosidic bond. In aqueous solution, there is an equilibrium of α- and β-D-form of the glucose part due to mutarotation, partly also in open-chain form. Due to the glucose residue present, lactose as a reducing sugar gives a positive Tollens or Fehling sample. With the Wöhlk reaction it is possible to distinguish lactose (salmon red colour) from glucose (yellow colour) and sucrose (colourless).

When heated or in alkaline solution, lactose is partially converted into lactulose, which tastes sweeter than milk sugar.

Further information: Wikipedia "Lactose"