Samenvatting
Samenvatting Food Chemistry
- Vak
- Food Chemistry
- Instelling
- Wageningen University (WUR)
In dit document heb ik alle learning outcomes uitgewerkt van ieder hoofdstuk.
[Meer zien]Voorbeeld 4 van de 85 pagina's
Voorbeeld 4 van de 85 pagina's
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Voorbeeld van de inhoud
Carbohydrates§1.2 Classification of carbohydrates
§1.2.1 Monosaccharides
☐ Know and recognize aldose/ketose, hexose/pentose, pyranose/furanose, α/β
Aldose (aldehydes): =O is connected to C1
Ketose (ketones): =O is connected to C2
Hexose: 6 C-atoms in the main chain
Pentose: 5 C-atoms in the main chain
Pyranose: 6 membered ring
Furanose: 5 membered ring
Ringform >99%
Anomeric carbon: Carbon between two oxygen groups
α-anomer: OH group on the anomeric carbon points down
β-anomer: OH group on the anomeric carbon points up
☐ know that D/L-enantiomers are mirror images
Highest numbered chiral carbon atom: next-to-last carbon
D-enantiomer: OH group on the highest numbered chiral carbon atom positioned on the
right in the Fisher projection
L-enantiomer: The hydroxyl group on the highest numbered chiral carbon atom positioned on the
left in the Fisher projection.
☐ know and recognize the anomeric carbon in a saccharide
The hydroxyl group OH and carbonyl group =O can react
→ cycle (cyclic hemiacetal) with anomeric carbon (between two O groups)
☐ Understand what a reducing sugar is
All monosaccharides can be in open and closed form.
Open form is reactive = reducing sugar
E.g. reaction with Cu2+, reduces coper
,☐ Recognize the structure of a reducing sugar
The OH group on the anomeric carbon is free
☐ know the importance of a reducing sugar for reaction
Reducing sugars
- Monosaccharides: all
- Disaccharides: almost all
- oligo-, polysaccharides: reducing ends
Reducing sugars are reactive at elevated temperatures
They can cause two types of browning reactions
- Caramelization
- Maillard
☐ Know what mutarotation is and the effect it has on optic rotation
Mutarotation, dependant in temperature
- Converting from one anomeric to another through the open ring structure
o Between α-and β.
o Between pyranose and furanose
Optic rotation
- Anomers differ in optic activity
- Polarize light beamed through sugar solution→ the different anomers rotate the plane of
polarization differently (mutorotation) → optic rotation of a solution can be measured →
changes of the sugar can be measured
☐ Recognize the general structure of a monosaccharide
Monosaccharides are the simplest unit of carbohydrates. They're composed of carbon, hydrogen,
and oxygen atoms, and they cannot be broken down further since they are already in their simplest
form
☐ Recognize the difference between the structures of the different monosaccharides
Glucose
- Obtained by hydrolysis of starch
- Mild sweetener in foods
- Naturally in fruits, honey (most abundant in nature)
- Building block of starch and cellulose
Types
- D(+)-glucose = Dextrose (alsohexose)
- B/D are mostly used B=D, C=E.
- α-form (+112)stronger optic rotation than β (+19). In solution → mutarotation
20 degrees C water → 1/3 α-and 2/3 β → equilibrium rotation (+53)
,Fructose
- obtained from corn starch and inulin
- HFCS (high fructose corn syrup is produced)= syrupy fluid of fructose, glucose, small amounts
of non-hydrolysed oligo- and polysaccharides
o Starch → glucose
▪ 95 % starch converted to D-glucose by α-amylase and gluco-amylase
o Glucose→ fructose
▪ 45% of the glucose converted to fructose by glucose isomerase
▪ Fructose: high sweetening capacity
Less dental caries than glucose and saccharose
Diet sugar for diabetics
- D(-)-fructose = ketohexose, pyranose (79%), furanose (21%)
- β form (-132 )stronger optic rotation than α- .
- In solution → mutarotation 20 degrees C water → equilibrium rotation (-92)
Mannose
- slightly sweet sugar
- building block of polysaccharide e.g. mannan
- component in coffee beans
Galactose
- building block of oligo-and polysaccharides e.g.
- lactose, raffinose, stachyose
- pectin and different mucilages, microbial exopolysaccharides (yoghurt)
Xylose
- aldopentose
- building block of xylans
- xylose and the alditol xylitol are sweet
- used in diabetic foods
Arabinose
- building block of hemicelluloses pectin, mucilages
- mostly in furanose form
, ☐ Know and recognize the general structure of uronic acid
Uronic acid
- monosaccharides
- OH group at C6 is oxidised to a carboxylgroup (COO- or COOH)
- E.g. Galacturonic acid. Uronic acid of galactose in pectin
☐ Understand the effect of pH on the charge of uronic acid
pH low: COOH (neutral)
pH > 4: COO- (negatively charged)
§1.2.2 disaccharides
☐ Know and recognize and be able to draw glycosidic linkages
Monosaccharides can be linked through glycosidic linkages
Form oligo and polysaccharides
- Hemiacetal OH groups bond
o Nonreducing
- Hemiacetal OH and alcoholic OH bond
o Reducing
☐ know the definition of a disaccharide
Disaccharide is made out of two monosaccharides
☐ understand the systematic name of oligosaccharides
Saccharose: O- α-D-glucopranosyl-(1→2)-β-D-fructofuranoside
- Contains of two sugars glucose and fructose
- Linked 1,2 (C1 glucose and C2 fructose)
- Glucose α form, fructose β form
☐ Know what an invert sugar is
Invert sugar: obtained from saccharose hydrolysis to a 1:1 mixture of glucose and fructose
☐ Know the monomeric units of saccharose, lactose, maltose
Saccharose: Glucose + Fructose Lactose: Galactose + Glucose Maltose: Glucose 2x
O- α-D-glucopranosyl-(1→2)-β-D-fructofuranoside O- β -D-galactopyranosyl-(1→4) -D-glucopyranose O- α -D-glucopyranosyl-(1→4) -D-glucopyranose
- Table sugar - milk sugar - syrups
- Hemiacetal OH group bond - digestion β-galactosidase (lactase) - reducing ends
- No mutarotation - lack, lactose-intolerant
- No reducing ends - hemiacetal OH glucose stays intact
- mutarotation
- reducing properties
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