Starch Chemistry:

Starch consists of two glucose polymers: amylose and amylopectin. Although both polymers are composed of D-glucopyranose molecules,dissimilarities between the two polymers result in major differences in characteristics.

Amylose and amylopectin do not exit free in nature,but as components of the starch granules.The size,shape and structure of the granules vary substantially among botanical source.

Characteristic	Amylose	Amylopectin
Shape	essential linear	branched
Linkage	a-1, 4(some a-1, 6)	a-1,4 and a-1,6
Molecular weight	<0,5 million	50-500 million
Filmforming	strong	weak
Gelling	firm	soft
Colour with Iodine	blue	reddish brown

Starch	Amylose (%)	Amylopectin
Maize (corn)	25	75
Waxy maize	1-5	95-99
Wheat	25	75
Potato	20	80
Tapioca	17	83
High Amylose maize	50-70	30-50

IS there a way to determine the starch concentration in a solution using simple apparatus?

Yes, there is a way to determine the starch concentration in a solution (or, probably more usually in a suspension) but if you want to do it you will need to carry out a few experiments to perfect your method. Iodine solution, usually available in any school lab will turn starch a deep shade of blue. If you were to use iodine solution and drop it into samples containing different amounts of starch the more concentrated samples containing samples would turn a darker blue than the more dilute samples. The differences in blueness could be detected using a simple photometer (usually found in schools).To be able to test an unknown sample you would need to construct your own "calibration curve". A suggestion of how to start of is as follows:
1.Make up a batch of iodine solution so that you can use the same batch for all your tests.
2.Make up at least 10 dilutions of a concentrated starch suspension. Make this suspension by using a carefully weighed out amount of starch(you will probably need to order this from your school supplier if you don't have any)in a set volume of water-say 10ml.Dilute one in ten, one in ten etc until you have 10 samples, all 10 ml.
3.Add a small amount of iodine solution to each sample(one drop should do).
4.Measure each sample, together with plain water in the photometer and plot your readings(minus the reading for the water on its own)against concentration of starch. Construct a curve from your points.
5.Take 10ml of your unknown suspension and add 1 drop of iodine solution. Measure in the photometer and compare the reading you get with your curve. You should be able to estimate the amount of starch in your unknown sample.

Starch Granules
Starch is stored in plants in the form of granules. The granules first appear in the plant cell as minute points, growing rapidly to fill the cell. The granule is made up of stratifies layers of starch formed around the nucleus called a hilum .As these layers develop, the starch granule assumes a size and shape characteristic of the specific plant.

Tapioca starch granules vary in diameter form 5-35 microns, potato starch from 15-100 microns, maize from 5-25 microns, while rice starch granules are only about 3-8 microns in diameter. The shapes vary from near perfect spheres to flattened ovoids, elongated disks, polygons and many others. By observing the size and shape of the granule structure is , an experience individual can identify the plant source of a starch even in mixtures of dry starch. Variations in starch granules from different plants may be microscopically.
The granule structure is not just a loose agglomeration of glucose polymers. It is systematically structured with the starch molecules oriented in specific spherocrystalline patterns. If the starch granules in aqueous suspension are microscopically observed in polarized light, a typical Maltese cross pattern is observed.

Starch granules are essentially insoluble in cold water. Their unique functional characteristics are the result of three major changes they undergo when heated with water: gelatinisation (viscosity increase), pasting and retro gradation. Retro gradation is especially evident when amylose containing starches are cooled, resulting in water release(syneresis).