Isolation of Starch from Potatoes (Practical Protocol) – A Step-by-Step Guide

Isolation of Starch from Potatoes

AIM

To isolate starch from potatoes

Materials required

Before we start the isolation process, let’s first look at the materials required for the protocol.

• Potatoes
• Distilled Water
• Hydrogen Peroxide (H₂O₂)
• Sodium Chloride (NaCl)
• Cheesecloth or Muslin Cloth
• Beaker
• Bunsen Burner
• Funnel
• Glass Rod
• Spatula
• Petri Dish
• Analytical Balance

PROCEDURE

Now that we have prepared our materials and solutions, we can begin the isolation process.

• Wash the potatoes thoroughly to remove any dirt or debris.
• Peel the potatoes and cut them into small pieces.
• Place the potato pieces in a blender or food processor and add enough distilled water to cover them.
• Blend the potato pieces and water until the mixture is smooth and well-mixed.
• Pour the potato mixture through a cheesecloth or filter paper to remove any solid pieces. Collect the liquid in a glass or plastic container.
• Allow the potato mixture to settle for a few minutes so that the starch can separate from the liquid.
• Pour off the liquid, leaving the starch at the bottom of the container.
• Rinse the starch several times with distilled water to remove any impurities.
• Transfer the starch to a funnel lined with filter paper and allow it to drain.
• Place the funnel and filter paper in a glass or plastic container and add enough ethanol to cover the starch.
• Allow the starch to soak in the ethanol for at least 30 minutes to remove any remaining impurities.
• Place the glass or plastic container on a hot plate or stove and stir the ethanol and starch mixture to 60-70°C, stirring constantly.
• Allow the mixture to cool to room temperature, and then filter off the excess ethanol.
• Allow the starch to dry completely before using it for any further applications.

Filtration and Drying of Isolated Starch

After isolating the starch from the potatoes, the next step is to filter and dry it.

• Use a funnel and filter paper to filter the starch to remove any impurities.
• Place the filtered starch in a petri dish and allow it to dry in a warm place.
• Once the starch is completely dry, weigh it.

Properties of starch

• Examine a little starch under a microscope. Note down the characteristic shape of the granules.
• Boil a small amount of starch with water. Cools, then add iodine solution. Note the color.

Preparation of Soluble Starch

•  Suspend three grams of raw potato in 100ml of redistilled 95% alcohol. Add 0.75ml of concentrated HCI.
• Heat it over boiling water with a reflux condenser for twenty minutes.
• Add at once 1 N NaHCO₃Solution to neutralize 0.75ml of acid using methyl orange as an indicator.
• Decant through a filter paper and wash with several portions of alcohol. Dry at room temperature and pressure it.

REPORT

The experiment shows that starch can be extracted from potatoes having asymmetric rings and rounded rings. They show a blue color with iodine, which indicates the presence of starch.

The net yield of starch from potatoes in 250 grams of potatoes Solution is __________ /250 grams.