Starch Flashcards
what separates potato starch granules from other starch granules?
they are very large, and form very high viscosity pastes
the brabender is used to…
measure time- and temperature-dependent viscosity changes in starch upon gelation
corn starch granules are commonly shaped…
non-spherical due to being so tightly packed in the corn
lugol’s iodine is used to…
detect starch, or more specifically, amylose. Lugol’s iodine is a brown solution that turns black/dark blue in the presence of starches, as the iodine sneaks into the amylose helix and forms a dark complex.
what is a disadvantage of using lugol’s iodine?
if other small molecules in the product to be analyzed sneaks into the amylose coil, iodine cannot complex with amylose and will not stain darker
how does plant tissue behave upon cooking?
starch granules swell and gelatinize within cells, then pectin present in middle lamella between cells is degraded and cells separate.
how do starch granules in potato behave upon cooking?
the starch granules swell to fill out the whole cell
what is special about the temperature where potato starch granules swell?
it is relatively low, they start to swell at temperatures lower than other starches do
when, in gelatinization, do starch pastes have their peak viscosity?
when the granules are at their largest size but have not started to disintegrate
how can aroma compounds affect gelatinization?
they can force aggregation of amylose outside granules, and they may, if they have the right shape, sneak into the amylose helix and then the aroma is lost”
what is an important difference in potato starch gelatinization under shearing, compared to other starches like wheat starch?
in wheat starch, granules are not very fragmented and the amylose leaked out from them forms a continuous gel, which is quite solid-like. in potato starch gelatinization under shearing force, starch granules disintegrate almost entirely and the paste becomes like glue.
decreasing shear on potato starch before peak temperature can…
decrease granule fragmentation and enable amylose to form a continuous gel. this can be used when granules need to be retained during processing or as an additive
how do wheat starch granules swell?
they swell on the inside where they have a lot of amylose, and then open up.
how is wheat starch gelatinization affected by addition of sugar?
it changes the swelling behaviour as it protects granules from degradation, increasing the viscosity of the solution
how is wheat starch gelatinization affected by addition of an emulsifier?
emulsifiers protect the granules, and they disintegrade suddenly at a certain temperature rather than over a temperature range. emulsifiers are added to cake batters to stabilize air bubbles (industrially) but they also affect the starch!
