Transcript Digestibility carbohydrates

N-free extracts, digestible
carbohydrates
• monosacharides
– pentoses,
• ribose (RNS);
• deoxyribose (DNS)
– hexoses,
• glucose (grape sugar, blood sugar, brain
tissues, muscle tissues, starch, cellulose);
• fructose (fruit sugar, green leaves, fruits);
• mannose (its polymers contain yeasts and
bacteria);
• galactose (milk sugar component)
• disaccharides
– sucrose (glucose + fructose; beet sugar, cane
sugar, green leaves, fruits, vegetables)
– lactose (glucose +galactose, milk sugar)
– maltose (2 glucose, compound of starch)
• trisaccharides
– raffinose (glucose + fructose + galactose,
roots, molasses)
Monosaccharides
hexoses
pentoses
Disaccharides
sucrose
maltose
lactose
isomaltose
Sweetening effect of different
sugars
•
•
•
•
fructose
sucrose
glucose
lactose
1,5
1,0
0,6
0,4
• polysaccharides
– starch
• glucose
maltose
starch
dextrin
• 15-30% amilose + 70-85% amilopectin
•
•
•
•
important energy source
high digestibility
identifying parameter of different feedstuffs
grains 50-70%, potato 14-18%
– glycogen
• the stored polysaccharide in the animals (foods
of animal origin)
Composition of starch
amilopectin
amilose
Digestion and absorption of saccharides
• starch
• digestion starts in the mouth, saliva contains α-amilase
• starch molecules will be splitted to shorter chains, called dextrines
• the determinant part of starch digestion takes place in the small
intestine by the α-amilase of pancreatic juice
• the digestibility of some starches increase after heat treatment
(potato)
• disaccharides (maltose, sucrose, lactose)
• splitting to monosaccharides mostly the disaccharidase enzymes,
produced by the enterocytes (maltase, sucrase, lactase)
• young animals have high lactase activity, that declining with the age
• about 10-15% of adult people can’t produce enough lactase, resulting
lactose intolerance)
• some people and animals can’t secrete sucrase enough
Digestion and absorption of saccharides
Monosaccharides can get through the intestinal cell
membranes and reach the blood.
The membrane transport can be active (needs ATP energy) or
passive (doesn’t need energy)
• glucose, galactose sodium dependent active transport
• fructose facilitated diffusion (it is slower compared to
glucose)
• a fructose and galactose are converted to glucose in the
liver
• organic acids
– naturally occurring (oxalic acid, citric
acid)
– in fermented feeds (lactic acid, acetic
acid, butyric acid)
– as preservation materials (propionic
acid, formic acid)
• alkaloids, glycosides
– plants containing only in small
amounts
– have an influence on the smell,
savouriness
– they are anti-nutritív, poisonous,
(potato - solanin; lupine seeds -lupinin;
rape seed – glycosides)
N-free extract, starch and sugar content of some
feedstuffs (%)
N-free extr.
starch
sugar
wheat
68,8
61,1
2,7
barley
67,1
50,1
1,7
peas
52,9
41,1
5,6
lupin seed
33,1
8,1
4,6
extracted
soybean meal
30,2
6,7
9,6
milk powder
(defatted)
51,8
-
47,7
Human nutritional aspects
• In Hungary the energy intake, coming
from starch takes 42% of the total
• Nutritional goal would be 55-58%
• recommended sugar intake : 60g/day
• requirement: 30-40 g/day
• consumption: man: 92g/day
woman: 85g/day
• we use too much added sugar