HW - 5/22/13

Tonight's homework is to complete Part 1 of the new experiment. See below.

On Cooking: How Does It Affect Food?

Aim: Scholars develop hypotheses regarding how cooking affects the nutrient content of foods in order to understand how we change food

Introduction

Previously we discussed the merits of cooking and why humans have adopted it so readily. However, it is worth investigating if there are any potential drawbacks to cooking our food. Could the heat applied to food during cooking somehow change the components of food and their qualities? Let’s see.

As we should already know, vitamin C (ascorbic acid) is an important micronutrient and foods high in it should be part of our daily diet. But what if the methods we use to prepare (or preserve our food) affect vitamin C in foods in a negative way? Oh no! This begs the question: how does cooking affect the vitamin content of the foods we at?

Your task is to get to the bottom of this question and determine the effect of cooking on the vitamin C content in foods. Below are your parameters.

Parameters

1. You will (and can only) investigate among the following vegetables: tomatoes, broccoli, green peppers, and potatoes.

2. Your in-class cooking options are the following: simmering (heating the sample in water to below boiling (to about ~180°F)), boiling (heating the sample in water to 212°F), and roasting (heating the sample over an open flame). Outside of class, you can cook the sample as you please if your parents allow.

3. In order to determine how much vitamin C is in your raw/cooked food samples you are going to perform a titration. Remember, a titration is a method of analysis that allows you to determine precise quantity of a reactant by observing the precise endpoint of a reaction.

4. The reactions that you will be observing are the reaction between iodine and starch (which produces a blue-black color) and the reaction between iodine and vitamin C (which interferes and stops the reaction between iodine and starch). Basically, you will add an iodine solution drop by drop to a mixture of starch and your liquefied samples until you notice a color change. This color change means that all of the vitamin C has been used up reacting with the iodine you were adding in the following reaction: ascorbic acid + I₂ --> 2 I^- + dehydroascorbic acid. So what is the relationship between the amount of iodine used and the amount of vitamin C in the sample?

Procedure

Today’s tasks are: 1. to conduct background research in order to inform possible hypotheses 2. to develop and submit a quality hypothesis and 3. to begin planning your experiment so that you can test your hypotheses.

For your planning…

Hypothesis:

IV:

DV:

Controlled variables:

Control group(s):

Experimental group(s):

Observation/data table:

Procedure: