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Testing Biological Molecules in Food

Oct 31, 2024

Lecture Notes: Testing for Biological Molecules

Overview

This lecture demonstrates how to conduct tests for various biological molecules: lipids, proteins, carbohydrates (starch), and glucose. Each test uses specific indicators to identify the presence of these molecules in different solutions.

Lipid Test

  • Materials Used: Vegetable oil, water, brown paper.
  • Procedure:
    • Place one drop of vegetable oil and one drop of water on separate areas of a brown paper.
  • Expected Results:
    • Positive Control: Vegetable oil (contains lipids).
    • Negative Control: Water (does not contain lipids).
  • Purpose: Establish a reference for identifying lipids in unknown substances.

Protein Test

  • Materials Used: Water, pepsin, Biuret reagent.
  • Procedure:
    • Test tube 1: Water (negative control).
    • Test tube 2: Pepsin (positive control).
    • Add Biuret reagent to both test tubes.
  • Expected Results:
    • Negative Control: Biuret remains unchanged with water.
    • Positive Control: Biuret changes color with pepsin, indicating protein presence.

Carbohydrate (Starch) Test

  • Materials Used: Water, starch solution, Lugol's iodine solution.
  • Procedure:
    • Test tube 1: Water (negative control).
    • Test tube 2: Starch solution (positive control).
    • Add Lugol's iodine to both test tubes.
  • Expected Results:
    • Negative Control: No color change with water.
    • Positive Control: Color change with starch solution, indicating starch presence.

Glucose Test

  • Materials Used: Water, glucose solution, Benedict's solution.
  • Procedure:
    • Test tube 1: Water (negative control).
    • Test tube 2: Glucose solution (positive control).
    • Add Benedict's solution and heat.
  • Expected Results:
    • Negative Control: No color change with water.
    • Positive Control: Color change with glucose solution, indicating glucose presence.

Application to Food Items

  • Use reference tests to evaluate presence of lipids, proteins, starch, and glucose in unknown food samples.

Food Item Tests

  1. Half and Half:

    • Test results: Lugol's iodine, Benedict's, Biuret, Lipid test.

  2. Protein Shake:

    • Test results: Lugol's iodine, Benedict's, Biuret, Lipid test.

  3. Coconut Water:

    • Test results: Lugol's iodine, Benedict's, Biuret, Lipid test.

These tests help identify the presence of essential biological molecules in substances, which can inform nutritional or chemical analyses.

Full transcript