Lactose (milk sugar )-

Lactose 

Lactose is from carbohydrates and its chemical composition results from combination between glucose and galactose and classified as di succharide .

Enzyme which help in digestion lactose is lactase (milk enzyme ).

Lactose is less sweet sugar, sucrose is sweeter than lactose by 7 times .

Lactose is little sweet to avoid high consumption of milk which may results in bad results.

Lactose  is poor soluble in water.

Milk of human and green monkey is the richest milk in lactose because lactose percent in milk of human and green monkey  is about  7% while in cow and buffalo milk is about 5%.

There are two types of lactose, alpha and beta , alpha lactose is hydrated ( saturated with water ) so it is insoluble in water while beta lactose is non hydrated (  little not saturated with water ) so it is relatively soluble in water.

Hydrolysis of lactose :

Lactose is hydrolyzed by lactase in gastrointestinal tract into glucose and galactose while in yogurt manufacture is hydrolyzed by lactic acid bacteria into lactic acid and carbon-dioxide , so lactic acid in yogurt is the cause of high acidity and low PH .

When PH of milk reaches 4.5 , the activity of lactic acid bacteria is inhibited .

In yogurt manufacture , 1 ml lactose gives .8 ml lactic acid by lactic acid bacteria.

10 - 30 % of lactose in milk converts into lactic acid by lactase enzyme secreted by lactic acid bacteria  during yogurt manufacture .

Lactose intolerance :

Lactose intolerance is pathological condition occurs when lactase enzyme is not secreted , the cause of absence secretion of lactase is mostly genetic cause and enteritis.

In case absence of lactase enzyme in gastrointestinal tract , lactose is not absorbed , so lactose accumulates in small intestine and withdraws water into small intestine, under effect of sugar , water and anaerobic condition , pathogenic bacteria activate and cause diseased condition. 

In case  sever  accumulation of water , lactose and anaerobic condition cause paralysis of smooth muscle of intestine which results in diarrhea .

individuals who suffers from lactose intolerance , it is advisable to drink lactose free milk .

NB yogurt is forbidden to children who suffer from lactose intolerance because in yogurt , only part of lactose not all lactose  converts into lactic acid .

Nutritive value of lactose : 

1-lactose helps in absorption calcium and phosphorus in small intestine  , so prevent rickets disease .

2-fructose synthesis  needs lactose .

3-give energy without fattening .

4-activate beneficial bacteria .

Lactose and dairy manufacture :

1- sandiness ( due to beta lactose )

crystallization of  lactose occurs in ice-cream and condensed milk due to slow cooling during manufacture.

2-lactose gluss ( due to beta lactose )

hygroscopic activity (tending to absorb moisture from the air ) of lactose absorbs water to form glass like crystals.

3-cooked flavor 

is due to UHT ultra heat temperature , 137 c for 5 seconds .

4-brown color 

is due to Millard reaction .

To avoid brown color with low temperature and equal distribution of lactose. 

5-caramelization 

due to over heating lactose or oxidation .

Tags: food safety