Week 2 – Carbohydrates
- Simple carbohydrates
o Monosaccharides
Glucose
Fructose
Galactose (not part of our diet as
monosaccharide)
o Disaccharides
Maltose (GLU-GLU)
Sucrose (GLU-FRU)
Lactose (GLU-GAL)
- Complex carbohydrates
Hydrolysis
------------------> +
(glucose) (fructose)
Sugars = mono- and disaccharides
Sugar = sucrose
Blood sugar = blood glucose
Invert sugar: mixture of glucose and fructose (equal amount) obtained by enzymatic cleavage of
sucrose.
invert sugar is sweeter than sucrose.
It is used by food manufacturers to:
- Retard the crystallization of sugar
- Retain moisture in packaged food
High fructose corn syrup (HFCS): mixture of glucose and fructose
Corn starch converted from starch to glucose, followed by partial conversion of glucose to fructose.
The final ratio of fructose: glucose can differ. HFCS 55 means, that 55% is fructose and 45% glucose.
Complex carbohydrates:
polysaccharides:
- Glycogen (branched polymer of glucose present in meat)
- Starches
- Fibers (non-digestible and partly digestible carbohydrates)
Starch: amylopectin + amylose
Amylopectin (branched) Amylose (linear)
Dietary fiber are non-digestible carbohydrates will reach the colon mostly intact. Fibers may be
digested by bacteria in the colon.
, Soluble fiber: pectin, certain hemicelluloses and fructans.
soluble fiber is a chemically heterogeneous group that includes pectins and some hemicelluloses.
- Pectin: abundant presence of galacturonic acid. Pectin is added during food manufacturing to
impart gelation, viscosity, texture and protein stability. Often used in jams and jellies because
it forms stable gels.
- Hemicelluloses:
o Xylans
Arabinoxylans
Glucoronoxylans
o Mannans
Galactomannans (guar gum)
Glucomannans (xanthan gum)
o Xyloglucans
o Beta-glucan
- Fructans: Polymers of fructose
e.g. highly fermentable inulins. Different inulins are distinguished based on the degree of
polymerization. In addition, inulin is added to foods as a functional pre-biotic food ingredient
to confer a health benefit.
Insoluble fiber: cellulose, lignins and resistant starch
- Cellulose (not fermentable at all):
linear chain of glucose, similar to amylose, except the glucose units are linked in different
way by which that digestive enzymes cannot break them.
- Lignin: complex polymers of aromatic alcohols (no carbohydrates)
- Resistant starch:
o Physically inaccessible starch
o Granular starch
o Retrograded starch
o Chemically modified starch
Three fibers categories:
1. Fiber already present in food
2. Added, but obtained from food raw materials
3. Added, as synthetic carbohydrate polymers
Processing of fiber-rich foods often results in significant reduction in their fiber content.
Carbohydrate digestion:
- In the mouth: salivary glands produce amylase to break down starch in food (very incomplete
due to short time in mouth) starch to small polysaccharides and glucose amylase is
inactivated by acidic environment of stomach
- In the duodenum, pancreatic juices mix with content of stomach. Pancreatic juices are
bicarbonate-rich, raising the pH towards neutrality. Pancreatic amylase activity raises.
starch to maltose and glucose.
- In the intestines, enterocytes produce lactase, sucrase and maltase. All these reactions will
result in monosaccharides.
- Simple carbohydrates
o Monosaccharides
Glucose
Fructose
Galactose (not part of our diet as
monosaccharide)
o Disaccharides
Maltose (GLU-GLU)
Sucrose (GLU-FRU)
Lactose (GLU-GAL)
- Complex carbohydrates
Hydrolysis
------------------> +
(glucose) (fructose)
Sugars = mono- and disaccharides
Sugar = sucrose
Blood sugar = blood glucose
Invert sugar: mixture of glucose and fructose (equal amount) obtained by enzymatic cleavage of
sucrose.
invert sugar is sweeter than sucrose.
It is used by food manufacturers to:
- Retard the crystallization of sugar
- Retain moisture in packaged food
High fructose corn syrup (HFCS): mixture of glucose and fructose
Corn starch converted from starch to glucose, followed by partial conversion of glucose to fructose.
The final ratio of fructose: glucose can differ. HFCS 55 means, that 55% is fructose and 45% glucose.
Complex carbohydrates:
polysaccharides:
- Glycogen (branched polymer of glucose present in meat)
- Starches
- Fibers (non-digestible and partly digestible carbohydrates)
Starch: amylopectin + amylose
Amylopectin (branched) Amylose (linear)
Dietary fiber are non-digestible carbohydrates will reach the colon mostly intact. Fibers may be
digested by bacteria in the colon.
, Soluble fiber: pectin, certain hemicelluloses and fructans.
soluble fiber is a chemically heterogeneous group that includes pectins and some hemicelluloses.
- Pectin: abundant presence of galacturonic acid. Pectin is added during food manufacturing to
impart gelation, viscosity, texture and protein stability. Often used in jams and jellies because
it forms stable gels.
- Hemicelluloses:
o Xylans
Arabinoxylans
Glucoronoxylans
o Mannans
Galactomannans (guar gum)
Glucomannans (xanthan gum)
o Xyloglucans
o Beta-glucan
- Fructans: Polymers of fructose
e.g. highly fermentable inulins. Different inulins are distinguished based on the degree of
polymerization. In addition, inulin is added to foods as a functional pre-biotic food ingredient
to confer a health benefit.
Insoluble fiber: cellulose, lignins and resistant starch
- Cellulose (not fermentable at all):
linear chain of glucose, similar to amylose, except the glucose units are linked in different
way by which that digestive enzymes cannot break them.
- Lignin: complex polymers of aromatic alcohols (no carbohydrates)
- Resistant starch:
o Physically inaccessible starch
o Granular starch
o Retrograded starch
o Chemically modified starch
Three fibers categories:
1. Fiber already present in food
2. Added, but obtained from food raw materials
3. Added, as synthetic carbohydrate polymers
Processing of fiber-rich foods often results in significant reduction in their fiber content.
Carbohydrate digestion:
- In the mouth: salivary glands produce amylase to break down starch in food (very incomplete
due to short time in mouth) starch to small polysaccharides and glucose amylase is
inactivated by acidic environment of stomach
- In the duodenum, pancreatic juices mix with content of stomach. Pancreatic juices are
bicarbonate-rich, raising the pH towards neutrality. Pancreatic amylase activity raises.
starch to maltose and glucose.
- In the intestines, enterocytes produce lactase, sucrase and maltase. All these reactions will
result in monosaccharides.
