Carbohydrate reactions

Question 1

How are aldonic acids formed?

Answer 1

the aldehyde group of aldoses is oxidized into carboxyl resulting in carboxylic acid group

Question 2

what is is it called when the carboxylic acid is on an aldose? and what is the complemntary base, the salt called?

Answer 2

1. aldonic acid
2. aldonate

Question 3

aldonates have many applications what are some of them and why?

Answer 3

The why: gluconate salts from at a higher PH

1. sodium-D-gluconate is uses as a persavative that is allowed to be a food additive
2. calcium-D-gluconate is used for calcium fortification
3. Copper, zinc, iron-D-GLuconates are used for nutritional supplemnets

Question 4

why are Copper, zinc, iron-D-GLuconates used for nutritional supplments?

Answer 4

because they are more soluble than other salts

Question 5

why is calcium-d-gluconate used for calcium fortification?

Answer 5

because there is no taste, no odor and is very bioavailable. It is also not irratating to the gastrointestinal tract.

Question 6

How do redox reactions help in quantative determination of sugars like glucose and lactose?

Answer 6

In the redox reaction, the aldehyde group of a reducing sugar (like glucose or lactose) is oxidized to a carboxylic acid, reducing another reagent (like copper in Fehling’s solution and silver in tollens) which changes color, indicating the presence of the reducing suga

Question 7

What distinguishes aldoses from ketoses in the context of reducing sugars?

Answer 7

Aldoses have an aldehyde group that can directly participate in redox reactions, making them reducing sugars. Ketoses, which have a ketone group, generally do not participate unless they undergo isomerization to form an aldose.

Question 8

How can ketoses show a positive result in tests for reducing sugars?

Answer 8

Ketoses like fructose can isomerize to aldoses under alkaline conditions, which then allows them to participate in redox reactions as reducing sugars.

Question 9

Example of a ketose that can act as a reducing sugar under specific conditions.

Answer 9

Fructose is a ketose that can tautomerize into an aldose such as glucose or mannose in alkaline conditions, allowing it to show a positive result in tests for reducing sugars.

Question 10

What are uronic acids/how do they form?

Answer 10

they are formed from selective oxidation of primary alcohols of monosachrides. A primary alcohol is the alcohol attached to a carbon atom at the end of the carbon chain that is only bonded to one other carbon atom.

Question 11

What are aldaric acids/how do they form?

Answer 11

They form from the oxidation of both aldehyde groups and primary alcohols on monosachrides resulting in both ends of the molecule being oxidized

Question 12

in what conditions are aldaric acids fromed?

Answer 12

• in the presence of hot nitric acid
• formed by special enzymes as well

Question 13

How are lactones formed?

Answer 13

They are formed from aldonic acids undergoing an esterfiactin reaction in wich an ester is formed from an alcohol and carboxyl. This is a intramolecular reaction that forms a cyclic ester, hence the name lactone. This reaction is catalyzed by glucose oxidase or hexose oxidase

Question 14

What type of rings can be formed

Answer 14

1. 6 membered ring (1,5 or δ)
2. 5 membered ring (1,4 or γ) which is more often stable

Question 15

what are the uses of lactones D-glucono-δ-lactone (GDL)

Answer 15

1. used in industrial baking for leaving agent in refigerdated/frozen doughs since during baking there will be reversion to D-gluconic acid which is a leavening agent since it reacts with bicarbonate and releases CO2
2. Used in the manufacturing of some cheeses since it has the same effect as lactic acid but lowers the cost since no fermenation
3. Used in fish products to lower pH and then increase antimicrobial effect of perseving agent
4. used in canning of frozen fruits and veggies since it can interact and remove iron that catalyzes enzymatic browning reaction so color remains good
5. Used for bread dough improvment because adding enzymes will make GDL and hydrogen peroxide which is a powerful oxidant which can replaced oxidants that shouldnt be used

Question 16

What is the result of reduction of carbonyl groups?

Answer 16

In carbohydrates will add H2 to the aldehyde or ketone group forming alditol→also known as polyhydroxy alchol, sugar alchol

Question 17

what are polhydroxy alcohols?

Answer 17

• not sugars since no aldehyde or ketone group, not reducing, and cannot be in malliard reactions
• resistant to strong acid/base conditions
• low in calories
• sweet and can sub sucrose
• not fermentable by most bacteria

Question 18

Briefly describe the following sugar alchohols: Erythritol,mannitol,sorbtiol

Answer 18

1. sorbitol: exists natrually in low [], it is comerically made by catalytic hydrogentation, one of the most common sweetneer, crystaline in solide state
2. Mannitol: is the reduction product of D-mannose made comerically and is found in high fructose corn syrup, can also make sorbitol, crystaline in solid state, not very soluble
3. erythritol: product of D-erythrose through fermnation, not D or L, non chrial, very low caloric value, anti-cariogenic

Question 19

rate these sugars in terms of sweetnes releative to succrose: erythritol, mannitol, srobitol

Answer 19

erthritol (1)→manitol + sorbital (0.5-0.7)

Question 20

how does caramelization reaction occur?, what are the steps?

Answer 20

1. dehydration-remove water
2. decomposition-break down the sugar
3. condenstation: individual sugars loose water and react with each other
4. isomerization
5. cyclation

Question 21

what happens during the process of caramelization?

Answer 21

Volatile chemicals are released which produce the caremal flavour. Results in a complex mix of polymeric compounds most of which are unsaturated, cyclic, low molecular weight and aroma compounds

Question 22

what is an example of one of the compounds released during caramelization?

Answer 22

Melanoidin which has low moleculr weight

Question 23

What are the four classes of cameral colors?

Answer 23

1. heating in the absence of ammonium/sulfite ions→brown soluble
2. heating in the presence of sulfite ions→rarely used
3. heating in the pressence of ammonia ions→brown, collodial particles
4. heating in the presence of both sulfite and ammonium ions→ brown, lower pH so used in acidc bervages, collodial partciles

Question 24

What are acids, based and salts used for in caramilzation?

Answer 24

used to adust color and flavour compounds

Question 25

why is caramelization different from malliard?

Answer 25

it happens at higher temperatures, no AA and involves pyrolysis of sugars

Question 26

what are the steps of the malliard reaction?

Answer 26

1. Sugar + amino acids heated a high temp→(colourless)
   
   1. Schiff base: formation is realy the first step, a glycosylation rxn between protiens and carbs, there must be no reductive agent since it stabilizes schiff base
   2. Amadori adduct- fromed by the isomeration of shciff base.
   3. Dehydration and fragmentation of intermediats resulting in the oxidation of amadori compound which leads to aromatic compound products like HMF and pyruvaldehyde
   4. aldol condensation and futher reactions lead to polymerization which results in melanoidins which result in different aroma and brown color

Question 27

how is malliard reaction controlled?

Answer 27

• temperature (decrease it and decrease rxn rate)
• pH (decrese=decrease reaction rate)
• wayer content adjustment
• more reactive sugars so reducing sugars with/without certain amino acids to create browning
• sorbitol so non reducing can be used to avoid browning
• metal ions

Question 28

what is acrylamide?

Answer 28

a product of the malliard reaction which is formed from reducing sugar and free aspargine in foods and is a carcinogen, so asparaginease is used to reduce amount

Question 29

where is malliard used, specific example

Answer 29

maple syrup. Sucrose is converyed to glucose and fuctose, the glucose will react with amino acids in sap during evaporation.