Food chem carbs 6 Flashcards
What are starches
-starch is a polymer of glucose
-starch is a homopolysaccharide
-in starch, the monosaccharides are joined by alpha glycosidic linkages
-found in roots and seeds of plants
-animal and human depend on plant starches for nourishment.
-acts as thickening agent, stabilizers, gelling agents etc.
what are the two types of starches
amylose(unbranched) and amylopectin(branched)
what are amylose and amylopectin
amylose are linear chains of several thousands of glucose units joined by alpha -1,4 glycoside linkages.
amylopectin are branched networks made up of alpha-1,4 glycosidic linkages and alpha-1,6 glycoside linkages.
describes starch gelatinization
when starch is heated in water, disruption of the molecular arrangement of within the starch granules occur.
during heating, the starch granules swell as water enters the granule.As the water continues to migrate into the starch granules, it forms hydrogen bonds with the amylose and amylopectin molecules.Some amylose molecules also leak out of the granules and move into the solution.
Gelatinization occurs over a range of temperature
what are thin boiling starches
thin boiling starches are granular products obtained from hydrolysis of the glycosidic bonds in starch using hot acids. produce more vicious solution and has higher molecular weight
WHAT ARE DEXTRINS
Dextrins are produced from high degree of depolymerization of starch
and are lower molecular weight carbohydrates (short chain)
produce lower viscosities at equal conc than thin boiling starches
what test to test for presence of starch
iodine test
explain iodine test with starch
limitations of native starch
-weak paste formation, low viscosity paste
-moisture exuding
how to improve properties of native starch?
by chemical modification process through cross-linking to produce cross-link starch eg of modified starch: starch acetates and hydroxypropyl starches
