carbohydrates Flashcards
what is photosynthesis
the process by which green plants use energy from the sun to change carbon dioxide and water into glucose and oxygen
what are the three types of carbohydrates
monosaccharides, disaccharides and polysaccharides
what is a monosaccharide
one sugar unit, C6H12O6, examples are fructose, glucose and galactose
what are disaccharides
they are formed when two monosaccharides join together with the elimination of water, examples are maltose, sucrose and lactose. the chemical formula is C12H22O11
What is a polysaccharide
formed when two or more monosaccharides join together with a loss of a water molecule each time, they may be straight or branched. examples are starch, pectin, gums and glycogen, their chemical formula is n(C6H10O5)
What are NSPs?
nonstarch polysaccharides that cannot be digested and absorb large amounts of water
what is peristalysis
the muscular movement of food along the gut
what are sources of NSPs
wholemeal bread, brown rice and wholemeal pasta
what are the properties of sugar
solubility, flavour/sweetness, assists aeration, caramelisation, crystalisation, hydrolysis, inversion, Maillard
what is solubility of sugar + culinary app
sugar is soluble in water, a syrup is formed when a large amount if sugar is dissolved in a small amount of water, culinary ap is canned peaches to preserve
what is the flavour of sugar + culinary app
sugar is sweet and gives an appetising flavour to food, sweetness is measured on a percentage scale for example fructose is 170%, culinary app: shortbread
what is asissts aeration of sugar + culinary app
occurs when sugars are whisked with egg whites, sugar helps to denature the egg protein, culinary app: meringues
what is the maillard reaction of sugar + culinary app
non enzymic browning of food due to a reaction between amino acids and sugars under dry heat results in an attractive brown colour and a crust with appetising flavour. culinary app: shortbread
what is caramelisation of sugar + culinary app
when sugar is heated it melts and caramelises which occurs over 10 gradual stages, caramelisation occurs at 160 degrees culinary app: creme caramel
what is crystallisation of sugar + culinary app
when a liquid has dissolved as much sugar as it can it is saturated, if more sugar is added crystals of sugar form and solidify when cooled. culinary app: fudge
what is hydrolysis of sugar
hydrolysis is the addition of a water molecule. disaccharides react with water and enzymes which breaks down sugar to two monosaccharide units
what are the properties of starch
flavour, solubility, hygroscopic, dextrinisation, gelatinisation and hydrolysis
what is inversion of sugar + culinary app:
inversion occurs when a liquid sucrose solution is heated in the presence of an acid or enzyme to split it into glucose and fructose, this is sweeter than sucrose, culinary app: jam making
what is the flavour of starch
not sweet
is starch soluble in water
it is insoluble in cold water
what is hygroscopic in starch
how starch absorb moisture from the air eg how biscuits soften if not kept air tight
what is dextrinisation + culinary app
dextrins are shorter chains of starch, on heaing, dextrins form longer chains and become brown coloured substances call pyrodextrins a culinary app is toasting bread
what is gelatinisation of starch + culinary app
as temperature rises, the mixture becomes even more viscous, forming a sol, on cooling this becomes a gel a culinary app is using flour to thicken soups and sauces
what is hydrolysis of starch
a chemical breakdown of a molecule by adding water to produce smaller molecules
what is dietary fibre
it is insoluble in water and cannot be digested by the body but gives bulk to the diet as it absorbs water as it passes through the intestinal tract and stimulates the removal of waste from the body by peristalsis, this speeds up the passage of food preventing bowel disorders
how would you increase fibre intake
reduce sugar intake and refined starch and include whole grains in the diet. choose brown bread, pasta and rice, add bran seeds and nuts and increase fruit and veg intake
what are gums + culinary app
they are soluble in water and have the ability to absorb large amounts of water to form a thick gel with a firm texture, culinary app: ice cream
what are the properties of pectin + culinary app:
naturally present in plant cells and cell walls of fruit and veg, used as a setting agent in jams and jellies as it has the ability to absorb water to form a gel. it is only present in fruits when they are ripe, pectin can only be extracted with heat and acid, culinary app: jam making
what are the effects of dry heat on carbohydrates
dextrinisation, caramelisation and maillard reaction
what are the effects of moist heat on carbohydrates
cellulose softens eg cooked vegetables, gelatinisation, inversion, solubility
biological functions of carbohydrates
used for heat and energy in the body, spare protein so it can be used for growth and repair, excess carbohydrates are converted to glycogen and stored in the liver and muscle as an energy reserve or stored as adipose tissue to insulate, cellulose/fibre moves food through intestine preventing constipation
describe the digestion of carbohydrates
salivary amylase breaks starch into maltose in the mouth, they are physically churned in the stomach, in the intestine, amylase in pancreatic juice breaks starch into maltose. in the intestinal juice: maltase breaks maltose into glucose, sucrase breaks sucrose into glucose and fructose , lactase breaks lactose into glucose and galactose.
how are carbohydrates absorbed in the body
monosaccharides are absorbed through the villi of the small intestine into the blood stream and are carried to the liver in the portal vein
