Prueba del Almidón-Yodo para Carbohidratos

Detección de almidón en muestras de alimentos usando solución de yodo

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

Objetivo

Usar la prueba de yodo para identificar almidón en varias muestras de alimentos y comprender la base molecular del complejo de color azul-negro.

Antecedentes

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.

Advertencias de seguridad

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

EPP requerido

goggles lab_coat

Materiales

  • 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)

Equipamiento

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

Procedimiento

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

Resultados esperados

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.

Limpieza

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

Detalles

Categoría
Qualitative Analysis
Dificultad
Beginner (Middle School)
Duración
30 min
Costo estimado
$5,00
Pasos
5
Materiales
5

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Frequently Asked Questions

What is the objective of Prueba del Almidón-Yodo para Carbohidratos?
Usar la prueba de yodo para identificar almidón en varias muestras de alimentos y comprender la base molecular del complejo de color azul-negro.
How difficult is Prueba del Almidón-Yodo para Carbohidratos?
This experiment is rated as Beginner (Middle School). It takes approximately 30 minutes to complete.
What safety precautions are needed for Prueba del Almidón-Yodo para Carbohidratos?
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 Prueba del Almidón-Yodo para Carbohidratos?
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 Prueba del Almidón-Yodo para Carbohidratos?
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.