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Functional foods > carbohydrates > Flashcards

carbohydrates Flashcards

1
Q

what are reducing sugars and non reducing sugars

A

reducing sugars can reduce some chemicals, with a free aldehyde or ketone group (open ring). non reducing sugars have a sealed ring and therefore are unable to reduce some chemicals

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2
Q

how can sugars bind

A

either hemiacetal (aldehyde) or hemiketal (ketone) reacts with alcohol to form glycosidic bonds. either an alpha or beta linkage (up or down configurations, which are fixed after bond made)

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3
Q

what is the chemical name and chemical symbol of maltose

A

chemical name
α-D-glucopyranosyl-(1-4)-D-glucopyranose

chemical symbol
αGlc_p [1-4]Glc_p

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4
Q

what is the chemical name and chemical symbol of isomaltose

A

chemical name
α-D-glucopyranosyl-(1-6)-D-glucopyranose

chemical symbol
αGlc_p [1-6]Glc_p
(_ means subscript)

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5
Q

what is the chemical name and chemical symbol of Lactose

A

chemical name
β-D-galactopyranosyl-(1-4)-D-glucopyranose

chemical symbol
β Gal_p [1-4]Glc_p
(_ means subscript)

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6
Q

what is the chemical name and chemical symbol of sucrose

A

chemical name
α-D-Glucopyranosyl-(1-2)-β-D-Fructofuranose

chemical symbol
αGlc_p [1-2]βFru_f
(_ means subscript)

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7
Q

what is the chemical name and chemical symbol of Fructose

A

chemical name
α-D-Fructofuranose

chemical symbol
α-D-Fru_f
(_ means subscript)

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8
Q

what is the chemical name and chemical symbol of Glucose

A

chemical name
β-D-glucopyrannose

chemical symbol
β-D-Glc_p
(_ means subscript)

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9
Q

what is the chemical name and chemical symbol of Galactose

A

D-Gal_p

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10
Q

what is the chemical name and chemical symbol of Mannose

A

D-Man_p

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11
Q

what are the three types of sugars and their examples

A

Simple carbohydrates (mono and polysaccharides), complex carbohydrates (starch and dietary fibres), and sugar alcohols (manufactured and added to foods as they are 0 calories as they cannot be digested)

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12
Q

what do the D and L for monosaccharides mean

A

they describe the stereo configurations of molecules (non super impossible mirror images of chiral carbon)

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13
Q

what are structural isomers and give an example

A

compounds with the same molecular formula but are arranged differently (D-Glucose and D-Fructose

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14
Q

what are enantiomers and what is an example

A

non superimposable mirror images (d and l sugars). D-Glucose vs L-Glucose.

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15
Q

what are stereoisomers

A

molecules that have the same molecular formulae and sequence, but differ in the spatial orientation of the atoms. (D-Mannose vs D-Glucose)

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16
Q

what are epimers and what is an example

A

diastereomic monosaccharides which have opposite configurations of a hydroxyl group at only one pair (D-Glucose and D-Mannose pair)

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17
Q

what is an anomer and what is an example

A

a pair of monosaccharides which differ only in the position of the CI-OH (carbon 1 in the ring form (alpha-D-Glucose and Beta-D-Glucose)

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18
Q

what is a conformer and what is an example

A

a pair of monosaccharides which differ only in their ring conformation (Pyran vs Pyranose)

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19
Q

what is the product of oxidation of sugars and what is the process

A

oxidation (loss of electron or hydrogen atom) produces a sugar acid. this is the oxidation of the aldehyde or keto functional group of the parent sugar

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20
Q

what are the oxidation and reduction products of glucose

A

oxidation: glucuronic acid (oxygen added to the aldehyde to make it a carboxylic acid)

reduction: D-Glucitol (CHO to CH2OH, the aldehyde is turned into an alcohol)

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21
Q

what is the product of reduction of sugars

A

it produces sugar alcohols by reducing (gaining electron or hydrogen atom) the aldehyde or keto functional group of the parent sugar

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22
Q

what are the biochemical actions of alpha amylase, and is it endo or exoenzyme

A

hydrolyses alpha-1,4-glucosidic bonds in a random fashion along the chain. produces corn syrup. it is an endoenzyme (meaning hydrolyses enzymes from the middle)

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23
Q

what are the biochemical actions of beta-Amylase, and what does it make

A

an exoenxyme which removes successive maltose units from the non-reducing end of the glucosidic chain. important in brewing and distilling to convert starches into fermentable maltose.

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24
Q

what are the biochemical actions of gamma-Amylase and what does it make

A

an exoenzyme (hydrolyses from ends) which removes Glc units in a consecutive manner from the non reducing end of the chain. it can also slowly attack the alpha-1,6 linkages at the branch point, meaning it completely degrades starch to Glc. Creates high glucose corn syrups from corn starch.

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25
Q

what are the biochemical actions of glucose isomerase

A

isomerisation of Glc to Fru. creates high fructose corn syrups

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26
Q

what are the biochemical actions of Sucrase

A

cleaves non reducing alpha-1,2 bond of sucrose. this turns sucrose into glucose and fructose, a product called the inverted sugar.

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27
Q

what is the degree of polymerisation

A

the average size of the polymer (how many sugars). larger number means larger average polymer size

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28
Q

what are the methods to determine DP

A

specific chemical reaction to determine number of reducing sugars and therefore number of oligomers

general chemical reaction to determine hexoses after strong acid hydrolysis, therefore the number of monosaccharide units

(basically count number of chains, then dissociate and find number of sugars, and divide).

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29
Q

what is mutarotation

A

the change in optical rotation of a sugar solution due to interconversion of alpha and beta forms of sugars until equilibrium is reached (pure solution of alpha will convert to equilibrium of alpha and beta changing optical rotation properties of solution). Equilibrium favours more stable compound. (the less dipole instability)

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30
Q

explain why mutarotation occurs in glucose

A

in alpha glucose there is dipole repulsion between hydroxyl groups, meaning beta is more stable in equilibrium

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31
Q

what are the basics of food browning

A

polymers lead to colour, small molecules lead to flavour

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32
Q

what is enzymatic browning

A

polyphenol oxidase catalyse the sequential hydroxylation and oxidation of monophenol to ortho-quinone. the o quinone condenses with other compounds to form dark brown colour. the damage of the cells is required to initiate browning because the enzyme is kept seperate. examples are cut apples and ripening of bananas.

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33
Q

what is needed for enzymatic browning?

A

polyphenol oxidase, and oxgen from the air, and therefore exposure to the air.

34
Q

what does polyphenol oxidase do?

A

it catalyses 2 reactions. it adds a hydroxyl group to the monophenol forming monocatechol, which is then oxidised into o-quinone.

35
Q

how does ascorbic acid (found in lemon juice) inhibit enzymatic browning

A

it is a reducing agent which prevents the build-up of o-quinone by reducing oxidised substrates

36
Q

how does vinegar prevent enzymatic browning

A

it reduces the pH which inhibits the PPO enzyme by denaturing it, reducing the browning.

37
Q

how does blanching cut vegetables prevent enzymatic browning

A

the high temperature denatures the enzyme PPO, inhibiting the enzymatic browning

38
Q

what are the methods of preventing enzymatic browning

A

blanching (denature through temp), vinegar (denature through pH), ascorbic acid (reduces o-quinone, preventing condensation to colour compounds)

39
Q

what is caramelisation

A

when sucrose are heated to high temp (>150 C) (in the absence of water) a darkening is observed. the sucrose is first broken down into two monosaccharides. then there are two competing reactions, a decomposition which forms small particles responsible for the flavour and aroma, and dimerisation (type of oligomerisation) which is responsible for the colour.

40
Q

what is the decomposition reaction of the caramelisation.

A

when the sucrose breaks down into two monosaccharides, it can further break down, from which a large number of molecules are derived, which are each responsible for different tastes and aromas.

41
Q

what is the dimerisation (Oligomerisation) reaction of caramelisation

A

when sucrose is undergoing caramelisation, it takes the form of isosacchrosan through oligomerisation. this can form caramelan (self assembly of singular into crystal structure, smallest), caramelin (three isosacchrosan into one and self assembly into crystal structure, medium), and caramelen (2 isosacchrosan forms largest with other reactions).

42
Q

what are the consequences of caramelisation (and if too much)

A

leads to nice flavours and colours in many foods. If it proceeds too far, the decomposition goes too far, destroying the sugar, removing the sweet taste, and forming other compounds. Eventually the flavour turns bitter.

43
Q

what are Maillard browning reactions?

A

it occurs when sugars are heated near amines such as from free amino acids or side chains of proteins. it can create a very wide range of compounds.

44
Q

how do the compounds produced in Maillard reactions differ to caramelisation?

A

the Maillard reaction products have a wider access to other molecules such as nitrogen. Therefore Maillard reactions can produce the same compounds, but can also produce more different compounds.

45
Q

what are the steps of Maillard reactions (and how do the colour compounds form)

A

sugar and amino group heated to a high temperature, forming an Amadori product which is rearranged before the amino group is removed. Then fragmentation and dehydration occur , forming smaller aroma and flavour compounds, leading to formation of colour compounds due to reactive groups on the molecules reacting with itself (aldol condensation) or other molecules, building up melanoidins.

46
Q

what is the process of Maillard reactions

A

sugar and amino group heated to a high temperature, forming an Amadori product which is rearranged before the amino group is removed. Then fragmentation and dehydration occur, forming smaller aroma and flavour compounds, leading to formation of colour compounds due to reactive groups on the molecules reacting with itself (aldol condensation) or other molecules, building up melanoidins.

47
Q

what are the effects of pH on Maillard reactions

A

reactions decrease in acidic pH (as acidity removes the nucleophilicity of amino group due to protonation) and increase in alkaline pH (maintains the amino group as the free form)

48
Q

what are strecker reactions

A

as a part of the side reactions of Maillard reactions (not forming malanoidins), the Maillard intermediates (Deoxyosones) react with other amino acids, forming important compounds.

49
Q

what is the product of Maillard reactions

A

Maillard reactions can result in colours, flavours, aromas, Antioxidants, nutritional loss, toxic compounds, mutagenic compounds.

50
Q

what is the product of Maillard reactions

A

Maillard reactions can result in colours, flavours, aromas, Antioxidants, nutritional loss, toxic compounds, mutagenic compounds.

51
Q

what are the health consequences of the Maillard reactions

A

Loss of essential amino acids (such as lysine), formation of glycation end-products such as pentisidine (sugars added to amino acids on proteins, which can be inflammatory and contribute to diabetes), formation of compounds that promote cross linkage of proteins in body (might contribute to diabetes), and formation of potential carcinogenic heterocyclic compounds in food (contribute to colon cancer due to oxidative nature).

52
Q

what are furosine and lactulose and how are they used to monitor milk quality?

A

they are both molecules formed in Maillard reactions when milk is heated during pasteurisation or processing. They indicate quality of milk, as they show how processed they have been, determining between raw, and pasteurised milk through to ultrahigh heated and milk powder.

53
Q

how is furosine formed

A

the lactose sugar and amino group of protein react together when heated forming Amadori products before acid hydrolysis turns it into Furosine.

54
Q

how is lactulose formed

A

lactose dissociates into Galactose and Glucose through Lactase. The glucose then isomerises into fructose, bonding to the galactose, forming lactulose (i think?)

55
Q

what is the effect of building up lactulose

A

as it requires lactose, it’s removing the sugar making it less sweet and changing the taste

56
Q

What are the sugar composition, linkages, and general properties of Amylose?

A

it is an alpha 1,4 linked Glc polysaccharide. the consecutive alpha linkages “kinks” the chain into helices. stabilised by hydrogen bonding between forward and backward sugars. Helical coil structure. (intramolecular hydro bonding)

57
Q

What are the sugar composition, linkages, and general properties of Amylopectin?

A

alpha 1,4 linked glc chains branches in alpha 1,6 linkage to the main polymer. the branches in chains reduce capacity to form regular structures, resulting in more expanded structure in solution. Branches also provide sited for enzyme binding, increasing digestion speed.

58
Q

what is starch retrogradation

A

loss of viscosity, shrinkage of gels, syneresis, expulsion of water, toughening of textures. This is where the interacting starches result in amylose reasociating, forming helixes, expelling the water which hydrated it. However, amylopectin does not

59
Q

In theory, we can predict that low amylose starch such as waxy starch would be less retrogradative than high amylose starch. Explain?

A

Retrogradation is related to recrystallisation of amylose

60
Q

what is resistant starch? and non-starch polysaccharides (nsp)

A

starch which is resistant to enzymatic digestion. nsp is any other polysaccharide which is not a starch, meaning that we cannot digest it, as we only have enzymes to break down starch.

61
Q

Where is starch digested?

A
  • in the small intestine. The specialised cells of the small intestine are called enterocytes. The enzymes in starch digestion are found in the microvilli of the small intestine.
62
Q

What enzymes are involved in starch digestion?

A
  • Pancreatic alpha amylase which polymerises large starch molecules like amylose and amylopectin into oligosaccharides, which are too large to be absorbed. Then mucosal alpha-glucosidases of which each are specialised to break particular bonds (e.g. alpha 1,4), producing absorbable glucose units.
63
Q

what are galacto-oligosaccharides

A

a range of dietary fibers which are Prodominantly galactose, but also include fructose and glucose. they are very effective prebiotics, but produce lots of gas (carbon dioxide, hydrogen, and methane.

64
Q

what are fructo-oligosaccharides

A

inulin. the fermentation of inulin is slower than galacto… and therefore more pleasant to the body.

65
Q

how are fiber polysaccharides classified

A

According to their main sugar in the polymer chain) glucans are polymer of Glc, Xylans are polymers of Xyl. they can also be classified into homopolysaccharides and heteropolysaccharides (only 1 sugar, or more than 1 sugar type), and branched, and unbranched.

66
Q

describe beta glucan

A

predominantly beta 1,4 linked cellotriose, cellotetrose and cellopentose linked by beta 1,3 linkages. (chains are 1,4 linked, and 1,3 links bond them together) fermentable.

67
Q

describe pectin

A

They are galacturoans. large polymer of linear D-GalA interspaces with some L Rhamnose. Highly soluble.

68
Q

describe galactomannans

A

gums. linear branched heteropolysaccharide of D-Man linked chain with single D Gal linked branch. High solubility and fermentability.

69
Q

describe carrageenan

A

sulphate galactans. repeating Gal_p-Gal_p disaccharide units.

70
Q

describe alginate

A

from seaweeds, are alginic acid polymers. Extended random coil polymers of beta D Manuronic acid and alpha L guluronic acid.

71
Q

what are low vs high methoxypectins, and how do each form gels. Under which conditions do each thrive

A

Degree of methoxylation. > or < 50%. Low forms gel with Ca+ ions, and is weaker at higher temps. High forms gel by hydrophobic interactions, and is stronger at higher temps.

72
Q

what is an oligosaccharide

A

a sugar of 3-10 units.

73
Q

methoxypectins, and how do each form gels. Under which conditions do each thrive

A

Degree of methoxylation. > or < 50%. Low forms gel with Ca+ ions, and is weaker at higher temps. High forms gel by hydrophobic interactions, and is stronger at higher temps.

74
Q

predominantly beta 1,4 linked cellotriose, cellotetrose and cellopentose linked by beta 1,3 linkages. (chains are 1,4 linked, and 1,3 links bond them together) fermentable.

A

beta glucan

75
Q

large polymer of linear D-GalA interspaces with some L Rhamnose. Highly soluble.

A

pectin

76
Q

linear branched heteropolysaccharide of D-Man linked chain with single D Gal linked branch.

A

galactomannans

77
Q

repeating Gal_p-Gal_p disaccharide units.

A

carrageenan

78
Q

Extended random coil polymers of beta D Manuronic acid and alpha L guluronic acid.

A

alginate

79
Q

where are alpha, beta, and gamma amylase found in nature

A

alpha is widely distributed in animals and plants, beta is found in fungi, higher plants, and bacteria, and gamma is found in bacteria and moulds

80
Q

Explain why a solution of glucose has 35% a-pyranose and 65% b-pyranose form similar to a solution of galactose, while a solution of mannose has the reversed proportion?

A

structure of hydroxyl groups in C2. Dipole on C1 and C2 interact and repel each other. For Mannose, the C2 is much further away on alpha config.

Functional foods (6 decks)

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