Organic Compounds in the Foods

Transcription

1 Organic Compounds in the Foods Purpose: This lab activity will help you understand the chemical composition (i.e., carbohydrates, proteins, and fats) of the foods that you eat. Materials we will be using: goggles test tubes test tube rack test tube holder hot plate and water bath potato, apple, egg white, oil indicator solutions (listed below) foods of your choice& wildlife foods s s: The following chemicals are used to determine the presence of organic compounds in food. : a yellowish brown liquid. When it comes into contact with starches (large carbohydrates) it causes a color change to a dark blue or purple : a greenish-blue liquid. When it comes into contact with simple sugars (small carbohydrates), a color change indicates the amount of sugar that is present. The range of colors is blue/green (+1) to yellow (+2) to orange (+3) to red/brown (+4). Reagent: a light blue liquid. When it comes into contact with proteins, it changes color ranging from pink to dark purple. : a red liquid. When it comes into contact with lipids, it colors the lipids (fats) red and forms a ring in a test tube. Lab Procedure: (Read all the directions for this activity before you begin your work!) PART I: DEMO Control Food Samples (Table 1) 1. Predict what you think will happen when each of the different indicators is added to the food samples (i.e., apple, potato, egg white, vegetable oil). To do this, place a + next to the indicator if you think it will be a positive test and a - next to the indicator if you think it will be a negative test. 2. Record your observations for the initial appearance in Table Watch as your teacher tests each of the prepared food samples using the appropriate indicators (e.g., with apple use ). 4. Record the appearance of your solution after the indicator was added in Table Explain what this means (use the information on the first page to help you draw conclusions) and record in Table 1. **PUT ON YOUR GOGGLES!! YOU MUST WEAR THEM FOR THE ENTIRE LAB EXPERIMENT!!** (No exceptions and no excuses!!!)

2 PART II: Test Your Own Food Samples (Table 2) You are trying to determine which of the organic compounds are found in your own food samples. You may discover that your food contains all of them! Test both of your food samples with EACH OF THE FOUR INDICATORS. 1. Take a SMALL sample of your food. If it is a solid, grind it with a mortar and pestle before you put it in the test tube. Add 10 ml of distilled water to the food sample and mix. If it is a liquid, put it directly in the test tube. Record your observations for the initial appearance in Table Predict what you think will happen when each of the different indicators is added to the food samples. To do this, place a + next to the indicator if you think it will be a positive test and a - next to the indicator if you think it will be a negative test. 3. Add the indicators to the appropriate test tube. Follow the instructions below for adding each indicator. a. : place 1-5 drops into your test tube and swirl it gently. b. : place 5-10 drops of into your test tube and swirl gently. Using the test tube holder, place the test tube into the warm water bath for at least 2 minutes. BE CAREFUL around the hot plate and the water bath!! c. Reagent: place drops of into your test tube and gently swirl. *** CAUTION*** reagent is extremely basic and can cause severe damage to your skin, eyes and clothes. If you spill any of the reagent, let me know and I will help you clean it up. If you get it on your hands or any other part of your body, wash it immediately under water in the sink. If you get it in your eyes, use the eye wash station immediately. d. : place 3-5 drops into your test tube and swirl gently. 4. Record the appearance of your solution after the indicator was added Explain what this means (use the information on the first page to help you draw conclusions) and record in Table 2. PART III: Test Wildlife Food Samples (Table 3) 1. Follow the same procedure from Part II to test two wildlife foods to determine which of the organic compounds are found in them. Use Table 3 to record your observations for the initial appearance, predictions, appearance after the indicator was added, and to explain what this means. **WHEN YOU FINISH THE LAB--EMPTY THE TEST TUBES AND CLEAN THEM THOROUGHLY!! **

3 PART IV: Where are these organic compounds found? (Table 4) When everyone completes their tests, we will gather data about what types of food have each of the major organic compounds and try to make some inferences about the diets of animals, specifically humans! ANALYSIS QUESTIONS: Answer the following questions on a separate sheet of paper and attach it to your data table. 1. What are the major organic compounds and why each is important to living things? 2. What controls (i.e., standards) were used in this lab? Why were they used? 3. Which compound is most common in foods that come from plants? Which compound is most common in foods that come from animals? 4. If you wanted to reduce the amount of fat in your diet, what foods would you avoid? 5. Imagine that you are asked to analyze and compare a food substance with standards for organic compounds. During your tests you observe a positive response with IODINE and BIURET REAGENT. What can you conclude about this food? 6. If you had a slice of deluxe pizza (cheese, sausage, pepperoni, mushrooms, onions, and peppers) and you test it with each of the test solutions from this lab, predict what your results would be. Be sure to explain what the test results mean. 7. Which foods do you think your body would use for a quick burst of energy? For energy when carbohydrates are NOT available? For building body parts?

4 Organic Compounds in the Foods We Eat Table 1: Control Food Products (Demo) Apple Potato after What does this mean? Egg White Vegetable Oil Table 2: Your Food Samples after What does this mean?

5 Table 3: Wildlife Foods after What does this mean? Table 4: Where are these organic compounds found? Simple Sugars (monosaccharides) Starch (polysaccharide) Proteins Lipids