MadSci Network: General Biology

Re: the potato is the source of a starch known as what?

Date: Mon Feb 26 20:57:46 2001
Posted By: Phyllis Stumbo, Staff, Nutrition, University of Iowa
Area of science: General Biology
ID: 982856048.Gb

There is no specific name for starch from potatoes, it is just 
called "potato starch".  Most native starches, whether from roots, tubers 
or cereals contain more amylopectin (the branched chain molecule) than 
amylose (the generally linear molecule).  This affects the physical 
properties of the starch, things like how well it thickens, whether 
cooking it with water forms a thick paste or thin gruel.  The branched 
chain starches are used in instant puddings and they remain soft after 
they are prepared whereas the more linear starches form a solid mass 
almost like a gel when cooked.

Generally tuber and root starch have about 80% amylopectin and 20% 
amylose, whereas, cereal starches (corn, wheat, rice, etc.) contain about 
75% amylopectin and 25% amylose.  Potato differ from one variety to 
another and new varieties and cultivars are expanding the definitions.  
For example, "waxy-type" cereals and roots contain 100% amylopectin and no 
amylose.  Scientists are continuing to change starch make-up at the 
molecular level.

This is an interesting question and an interesting area of study.


Phyllis Stumbo
University of Iowa

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