Stärke-Iod-Test auf Kohlenhydrate

Nachweis von Stärke in Lebensmittelproben mit Iodlösung

Qualitative Analysis Beginner (Middle School) 30 Min. ~$5,00

Ziel

Den Iodtest verwenden, um Stärke in verschiedenen Lebensmittelproben nachzuweisen, und die molekulare Grundlage des blauschwarzen Farbkomplexes verstehen.

Hintergrund

The starch-iodine test is one of the most visually striking qualitative tests in chemistry. Iodine (I₂) forms a deep blue-black complex with amylose, the helical component of starch. The iodine molecules slip inside the amylose helix, creating a charge-transfer complex that absorbs light strongly. This test does not work with simple sugars (glucose, sucrose) or with amylopectin alone, making it specific for amylose-containing starch.

Sicherheitswarnungen

  • Iodine solution stains skin and clothing
  • Do not taste any samples after adding iodine
  • Handle knife carefully when cutting food samples

Erforderliche PSA

goggles lab_coat

Materialien

  • Iodine solution (Lugol's) (10 mL)
    I₂/KI solution
  • Starch solution (1%) (10 mL)
    Positive control
  • Glucose solution (1%) (10 mL)
    Negative control
  • Food samples (Various)
    Potato, bread, rice, apple, etc.
  • Distilled water (50 mL)

Ausrüstung

Spot plate or small dishes Dropper pipettes Knife for cutting food samples White paper background

Durchführung

1

Place small amounts of each food sample and control solutions in separate wells of the spot plate.

5 Min.
2

Add 2–3 drops of Lugol's iodine solution to the starch solution (positive control). Observe the blue-black color.

3 Min.
3

Add 2–3 drops to the glucose solution (negative control). Observe that the color remains amber/brown.

3 Min.
4

Add 2–3 drops of iodine to each food sample. Record the color change observed.

10 Min.
5

Classify each sample as starch-positive (blue-black) or starch-negative (amber/brown). Record in a data table.

9 Min.

Erwartete Ergebnisse

Potato, bread, and rice should test strongly positive (deep blue-black). Apple and pure sugar solutions should remain amber/brown. The intensity of the blue color correlates with starch content.

Aufräumen

Dispose of iodine-treated samples in general waste. Rinse spot plates and pipettes with water.

Details

Kategorie
Qualitative Analysis
Schwierigkeit
Beginner (Middle School)
Dauer
30 Min.
Geschätzte Kosten
$5,00
Schritte
5
Materialien
5

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Frequently Asked Questions

What is the objective of Stärke-Iod-Test auf Kohlenhydrate?
Den Iodtest verwenden, um Stärke in verschiedenen Lebensmittelproben nachzuweisen, und die molekulare Grundlage des blauschwarzen Farbkomplexes verstehen.
How difficult is Stärke-Iod-Test auf Kohlenhydrate?
This experiment is rated as Beginner (Middle School). It takes approximately 30 minutes to complete.
What safety precautions are needed for Stärke-Iod-Test auf Kohlenhydrate?
Key safety precautions include: Iodine solution stains skin and clothing; Do not taste any samples after adding iodine; Handle knife carefully when cutting food samples.
What materials are needed for Stärke-Iod-Test auf Kohlenhydrate?
The main materials required are: Iodine solution (Lugol's), Starch solution (1%), Glucose solution (1%), Food samples, Distilled water.
What results should I expect from Stärke-Iod-Test auf Kohlenhydrate?
Potato, bread, and rice should test strongly positive (deep blue-black). Apple and pure sugar solutions should remain amber/brown. The intensity of the blue color correlates with starch content.