Carbohydrates Flashcards
Classify carbohydrates according to their structure and give two examples in each class?
Monosaccharides
A simple sugar that contains one simple sugar unit . It is the smallest unit of carbohydrates
Eg glucose and fructose
Disaccharide
Formed when two monosaccharides join resulting in the lose of a water
Eg maltose and sucrose
Polysaccharide
Formed when three or more monosaccharides join together resulting in the loss of a water molecule with a new link . Chains can be straight or branched
Eg starch and pectin
Write a brief note on a)pectin b)cellulose
Pectin.
Naturally present in plant cells and the walls of fruit and vegetables. It is used as a setting agent and has the ability to absorb water and from a gel. For pectin to be abstracted it needs heat and acid eg lemon juice
Cellulose
Insoluble in water. Cannot be digested by the body. Absorbs water as it passes through intestinal tract and stimulates peristalsis . This feeds up passage of food and waste and prevents bowel disease
What are 6 properties of sugar
Caramelisation Crystallisation Hydrolysis Inversion Solubility Sweetness
What is caramelisation and culinary application
On heating sugar melts and carmalises.
This occurs over ten gradual stages between 104 degrees to 177 degrees
Normally occurs at 160 degrees resulting in brown colour and sweet taste
Culinary application: caramel squares
What is crystallisation and culinary application
When a liquid has dissolved as much sugar as it can it is saturated
If more sugar is added crystals form in the solution and solidify when cool
Culinary application. Fudge
What is inversion and culinary application
When a liquid sucrose solution is heated in the presence of an acid or enzyme it causes the disaccharide to split to monosaccharides
Also know as an invert sugar
Culinary application. Jam-making
What is hydrolysis
The reverse of the condensation reaction occurs during digestion
Water and enzymes split disaccharide into two monosaccharides e.g lactose in glucose and galactose
What is soluabilty and culinary application
Sugar is a white crystalline compound
Soluble in water
A syrup if formed when a large amount of sugar is dissolved in a small amount of water
Culinary application. Canned fruit
What are the 6 properties of starch
Soluabilty Flavour Hydroscopy Gelatinisation Hydrolysis Dextrinisation
What is the rda of fibre
25-35g per day
Effects of dry heat on carbohydrates
Dextrinisation eg toasting bread
Carmalisation eg creme caramel
Mallard reaction eg roast beef
Effects of moist heat on carbohydrates
Syrup formation eg tinned peaches
Gelatinisation eg white sauce
Cellulose softens eg tomatoes
Pectin extraction eg jam
What are the 4 biological functions of carbohydrates
Supply the body with heat and energy. Keep body at 37 degrees and supply energy for all activity’s
Protein-sparing function. Protein can fulfill their primary function of growth and repair of cells rather than being used to produce energy
Fibre absorbs water as it passes through the intestinal tract which stimulates peristalsis. Speed up passage of food and water and prevent bowl diseases
Excess carbohydrates converted to glycogen and store in the liver and muscle as a long term energy reserves . Can be converted to fat and stored in adipose tissue to insulate the body
What is the energy value of carbohydrates
1g provides 4 kcal of energy
Absorption of carbohydrates
After digestion the monosaccharides are ready to be absorbed by the small intestine .
Pas through wall of villi and into the bloodstream
Hepatic portal vein transports monosaccharides to the liver
In the liver fructose and galactose be converted to glucose
Glucose is oxidised to produces heat and energy
Converted to glycogen and stormed in liver and muscle as a long term energy reserve
Digestion of carbohydrates in mouth
Pancreas
Small intestine
During digestion water and enzyme break carbohydrates into monosaccharides
Mouth. Food is chewed into small pieces by the teeth. Salivary glands secrete saliva which contains the enzyme salivary analyses which breaks down starch to maltose
Pancreas . Secretes pancreatic juices contains the enzyme amylase into the duodenum. Continues break down of starch to maltose
Small intestine. The ileum secretes intestinal juices containing the enzyme maltase which breakdown maltose to glucose and the enzyme sucrase which breaks down glucose to fructose and enzyme lactase which breaks lactose down to galactose
What is hyrdroscopy and culinary application
Starch has the ability to absorb moisture from the air
Can cause uncovered food to soften and lose crunch
Culinary application keeps cakes from drying out
What is dextrinisation and culinary application
When starch food is dry heated short chained polysaccharide called dextrins form
Further heating theses combine and form pyrodextrins
Causes colour change on food surface
Culinary application. Browning of bread to make toast
Assimilation of carbohydrates
Monosaccharides can be oxidised to produce energy
Monosaccharides are changed to glycogen and stored in the liver and muscle as an energy reserve
Excess carbohydrates are changed to fat and stored in the adipose tissue under the skin
What is gelatinisation
Starch is heated in the presence of water
Starch grains swell and burst and absorbs water
Results in thickening of the liquid
As temperature rises mixture become viscous forming a sol
On cooking this becomes a gel
Eg using flour to thicken soups
Two properties of non-starch polysaccharides
Pectin
Cellulose
