Carbohydrates
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what are the functions of carbohydrates
energy and carbon source energy store flavouring functional ingredient (gum, probiotics)
what are the 4 types of carbohydrate
monosaccharide disaccharide oligosacchardie polysaccharides
outline the characteristics of monosaccharides
• simple, one sugar unit • C3H6O3 • aldoses and ketoses
what are the characteristics of aldoses
has a carbon and a double bonded oxygen at the end of the chain contains an aldehyde group
what are the characteristics of ketoses
has a carbon and double bonded oxygen in the middle of the chain contains a ketone group
define chiral
cannot be placed on top of its mirror image
examples of stereoisomers
D-… L-…
what are the two chiral forms
enantiomers epimers
what is an enantiomer
mirror reflection compounds related by inverting the configuration at all asymmetric carbons OH group pointing left = L-glucose OH group pointing right= D-glucose
what is an epimer
disastereomers with an inverted configuration at one asymmetric carbon
what is a disastereomer
compounds related by inverting configuration at one or more chiral centres
what is meant by the cyclic structure of monosaccharides
reaction occurs between -OH at C-5 and the aldehyde at C-1, producing a pyranose ring this produces an new asymmetric centre at C1, with two new alpha and beta stereoisomers- called anomers alpha anomer- above the ring beta anomer- below the ring the anomie’s are interchangeable by mutarotation
give an example of a reducing sugar
all monosaccharides glucose, fructose maltose, lactose
give examples of naturally occurring food monosaccharides
glucose, fructose, lactose, ribose
how is the anomeric carbon configuration determined
glucose • CH2OH and OH are on opposite sides on the anomeric carbon • 6 membered ring= pyranose fructose • CHOH and OH are on the same side of the anomeric carbon • 5 membered ring= furanose
example of a disaccharide
maltose
how are disaccharides formed
the hemiacetal end is free to open or close the hemiacetal group of the alpha-delta-glucose reacts with the OH group of the beta-delta-glucose and forms a glycosidic bond two monosaccharides formed by the glycosidic bond
how is sucrose formed
glucose and fructose = sucrose head to head no free anomeric carbon so is non-reducing inversion on heating made by plants
sugar beet is…
UK grown and processed in 6 factories seasonal (Sept- March)
sugar cane is…
a tropical plant that is shipped raw to the UK processed all year in 1 UK factory has many uses (flavour, colour, sweetener)
how is lactose made
glucose and galactose head to tail reducing sugar
give an example of a non-reading sugar
sucrose, trehalose
how is trehalose made
glucose and glucose head to head energy storage in insects non-reducing sugar
what are polyols
sugar alcohols