Teste do Amido-Iodo para Carboidratos

Detecção de amido em amostras de alimentos usando solução de iodo

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

Objetivo

Usar o teste de iodo para identificar amido em várias amostras de alimentos e entender a base molecular do complexo de cor azul-preto.

Contexto

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.

Avisos de segurança

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

EPI necessário

goggles lab_coat

Materiais

  • 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)

Equipamentos

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

Procedimento

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.

Limpeza

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

Detalhes

Categoria
Qualitative Analysis
Dificuldade
Beginner (Middle School)
Duração
30 min
Custo estimado
$5,00
Passos
5
Materiais
5

Mais experimentos

Arco-Íris de Indicadores de pH 45 min Cromatografia de Pigmentos Vegetais 60 min Desafio de Identificação de Substâncias Desconhecidas 75 min Espectroscopia de Emissão de Chama 60 min Identificação de Cátions por Precipitação 90 min Teste de Beilstein para Halogênios 25 min Teste de Dureza da Água com Solução de Sabão 40 min Teste de Pérola de Bórax para Íons Metálicos 45 min Testes de Identificação de Ânions 60 min

Frequently Asked Questions

What is the objective of Teste do Amido-Iodo para Carboidratos?
Usar o teste de iodo para identificar amido em várias amostras de alimentos e entender a base molecular do complexo de cor azul-preto.
How difficult is Teste do Amido-Iodo para Carboidratos?
This experiment is rated as Beginner (Middle School). It takes approximately 30 minutes to complete.
What safety precautions are needed for Teste do Amido-Iodo para Carboidratos?
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 Teste do Amido-Iodo para Carboidratos?
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 Teste do Amido-Iodo para Carboidratos?
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.