Materials Required

• Extracted starch samples (wheat, corn, rice, potato, cassava)
• Microscope
• Microscope slides and coverslips
• Iodine solution (for staining)
• Droppers
• Distilled water

Procedure

1. Place a small amount of extracted starch on a clean microscope slide
2. Add 1-2 drops of distilled water
3. Carefully place a cover slip over the mixture
4. Observe under low power (×10) first to locate the field
5. Switch to high power (×40) for detailed examination
6. Stain with iodine solution if needed to enhance visibility

Wheat Starch Granules

• Shape: More or less round
• Arrangement: Honeycomb-like structure attached together in clumps
• Size: Vary in size (some small, some large)
• Features: Granules occur in clusters as they do in the wheat endosperm

Corn Starch Granules

• Shape: Polygonal (angular)
• Size: Diameter ranging from about 5 to 35 micrometres (μ)
• Features: Distinct angular edges; varies considerably in size

Rice Starch Granules

• Shape: Polygonal (nearly square or angular)
• Size: Average diameter of less than 5μ (very small)
• Arrangement: Well arranged, small and uniform in size
• Features: Attached together in nearly polygonal clusters

Potato Starch Granules

• Shape: Irregular oval
• Size: Range from about 20 to 100 microns in diameter (largest among common starches)
• Features: Oval or spherical shape; consists of both small and large structures

Cassava Starch Granules

• Shape: Generally oval or spherical
• Size: Range from 5 to 100 micrometres in diameter
• Features: Smooth rounded appearance; varies considerably in size

When conducting microscopic observations, record the following:

1. Sample identification — Source of starch (e.g., wheat flour, rice, potato)
2. Magnification used — Low power (×10) and high power (×40)
3. Observations — Shape, size, arrangement, and any distinctive features
4. Drawings — Clear diagrams showing the actual appearance under microscope
5. Comparisons — How the observed starch differs from others

Iodine solution is used to enhance starch visualization:

• Starch molecules form a helical inclusion complex with iodine
• The complex produces a characteristic blue-black color
• Helps confirm the presence of starch
• Makes granules more visible under microscope

Safety precaution: Iodine solution can stain skin and clothing; handle with care and wash hands after use.

In Tanzania, food vendors and small-scale food processors can use microscopic examination to verify the quality of starch-based products such as cassava flour (ugali flour), rice, and dried potatoes. For example, a market vendor in Dar es Salaam selling cassava starch can quickly check if the product is pure or adulterated with other starches by observing the characteristic oval-shaped granules under a simple microscope — a 50,000 TZS purchase of a basic microscope can help prevent losses from buying adulterated starch and ensure customer satisfaction.