What Are Carbohydrates?

Food Technology — Theory

Food Technology Theory

What Are Carbohydrates?

Produced by plants during photosynthesis
After eating plant foods, humans convert the carbohydrates into glucose
Glucose is the most abundant carbohydrate
Preferred source of energy for the blood, brain, and nervous system
Carbohydrate-rich plant foods make up the foundation of diets all over the world

Define - Carbohydrate chemically

Carbohydrates are organic compounds made up of carbon, hydrogen, & oxygen
Carbohydrates are polyhydroxy aldehydes(-CHO) or polyhydroxy ketones (-CO) and their derivatives
Commonly, the hydrogen & oxygen in the carbohydrates are present in 2:1 ratio as in water, from which the name carbohydrate (Carbon Hydrate) was derived. CHO are sometimes referred as saccharides meaning sugar.
Simple -CHO are called sugars
One of the simplest carbohydrates is glucose (C₆H₁₂O₆) or monosaccharide & they link together to form more complex carbohydrates (oligo or polysaccharides)
The names of most -CHO are characterised by ending "OSE" E.g., Glucose

Sugar	Common Name
Lactose	Milk Sugar — Glucose + Galactose
Xylose	Wood Sugar
Maltose	Malt Sugar
Fructose	Fruit Sugar

In animal organism the main sugar is glucose & storage CHO is glycogen,
In plant organism a wide variety of monosaccharides and oligosaccharides occur & the storage carbohydrate is starch
The structural polysaccharide of plant is cellulose
The gums are a group of polysaccharides obtained from plants, seaweeds and microorganisms

Did you know?

Carbohydrates are found on the surface of cells where they act as "road signs" allowing molecules to distinguish one cell from another. ABO blood markers found on red blood cells are made up of carbohydrates. They allow us to distinguish our body's blood type from a foreign blood type. Carbohydrates in our body prevent blood clots Ex.Heparin

Classification of Carbohydrates.

1.Based on number of carbohydrate units

Monosaccharides cannot be broken down to smaller carbohydrates
Disaccharides consist of two monosaccharide units joined together; they can be split into two monosaccharides. Sucrose (table sugar), can be broken down into glucose and fructose.
Oligosaccharides contain anywhere from three to nine monosaccharide units. Raffinose, stachyose, ABO blood group are oligosaccharides.
Polysaccharides are large molecules containing 10 or more monosaccharide units. Carbohydrate units are connected in one continuous chain or the chain can be branched.

2.Based on number of functional units

Monosaccharides that contain an aldehyde group are referred to as an aldose. It is at C-1. Those that contain a ketone group are referred to as a ketose. It is at C-2

Fig. Example for carbohydrate based on the functional group

Monosaccharides: Aldoses vs. Ketoses

Trioses: 3-Carbon Sugars (C₃H₆O₃)

Aldose (Aldehyde)

Glyceraldehyde

Ketose (Ketone)

Dihydroxyacetone

Pentoses: 5-Carbon Sugars (C₅H₁₀O₅)

Aldose

Ribose

Ketose

Ribulose

Hexoses: 6-Carbon Sugars (C₆H₁₂O₆)

Aldose

Glucose

Ketose

Fructose

3.Based of Number of carbons

Three carbons: triose
Four carbons: tetrose
Five carbons: pentose
Six carbons: hexose
Seven carbons: heptose

Fig. Example for carbohydrate based on the carbon count

Fig. Aldohexose and keto-pentose differ in the number of carbon atoms and in the type of carbonyl group they contain.

	O
	\|\|
	C		H

H		C		OH

H		C		OH

H		C		OH

H		C		OH

H		C		H

	OH

An aldohexose

	OH

H		C	H

	C	= O

HO		C	H

H		C	OH

H		C	H

	OH

A ketopentose

Aldehyde

Ketone

Fig. Most common basic and complex carbohydrates in human diet.

--- config: layout: fixed --- flowchart TB Title["<center>The principal carbohydrates in the human diet</center>"] --- Food["Food carbohydrates"] Food --- Poly["Polysaccharides"] & Dex["Dextrins"] & Free["Free sugars"] Poly --- NSP["Non-starch polysaccharides"] & Starch["Starch"] NSP --- Cell["Cellulose"] & Hemi["Hemicelluloses"] Hemi --- Pectins["Pectins: Rhamnogalacturonans Arabinogalactans"] & Xylans["Xylans: Xyloglucans Galactomannans β-Glucans"] & Gums["Gums and mucilages: Gum arabic, Tragacanth, Guar, Locust bean, Alginic acid, Carrageenan, Xanthan gum"] Starch --- Amy["Amylose Amylopectin"] Free --- Mono["Monosaccharides"] & Alc["Sugar alcohols"] & Dis["Disaccharides"] & Oligo["Oligosaccharides"] Mono --- MonoL["Glucose, Fructose, Mannose, Ribose, Deoxyribose"] Alc --- AlcL["Sorbitol, Mannitol, Dulcitol, Inositol"] Dis --- DisL["Sucrose, Lactose, Maltose, Trehalose"] Oligo --- OligoL["Raffinose, Stachyose, Verbascose, Fructans"] OligoL -.-> FructanNotes["Fructans / FOS Inulin: β2→1 fructan, α1→2 glucose Levan: β-fructans"] Dex -.-> DexNotes["Dextrin: Oligopolysaccharide α1→4, α1→6"] OtherNSP["Other NSP: 1. Pullulan - Branched maltotriose 2. Dextrans - Branched glucan α1→6, α1→3"] style Title fill:#90ee90,stroke:#333,stroke-width:2px style NSP fill:#ffffcc,stroke:#333 style Cell fill:#ffffcc,stroke:#333 style Hemi fill:#ffffcc,stroke:#333 style FructanNotes fill:#fff,stroke-dasharray: 5 5 style DexNotes fill:#fff,stroke-dasharray: 5 5