1. OBJECTIVE
Every day, we see the importance of a diet with foods that contain antioxidant molecules for the protection and repair of cells affected by the action of free radicals in our body.

This benefit is found in a wide range of oilseeds, fruits, vegetables and greens, so knowledge about their chemical compositions helps science identify the various antioxidant molecules that may be present, such as carotene, vitamin E and others.

To have this knowledge, it is necessary for the professional to know the various types of analysis and the theory that underpins them. How is it possible to classify the antioxidant capacity of each food?


At the end of this experiment, you should be able to:

Know in detail the preparation of reagent stock solutions, in order to guarantee the accuracy of the concentration and the reliability of the analysis;

Evaluate the experimental procedure for determining the antioxidant activity of foods;

Organize laboratory steps in accordance with the scientific basis and good laboratory practices;

Interpret the results obtained after analysis on equipment and calculations on the observed values.

2. WHERE TO USE THESE CONCEPTS?
The characterization of foods is of great importance so that the appropriate diet can be indicated for each health condition. In the food industry, in research or quality control sectors, laboratory activity helps to understand the properties of a product. The professional must know the laboratory practices involved in the analysis and the correct interpretation of the results obtained. Based on its findings, the economic, logistical, industrial and commercial areas involving food are impacted. Critical analysis of the results makes it possible to identify non-conformities regarding the product or even the protocol followed during sample preparation, recognizing errors in the process. In the end, this knowledge is capable of supporting whether a batch of products is suitable or not or whether the laboratory protocol needs adjustments.


3. THE EXPERIMENT
This experiment focuses on detailing the process of preparing solutions for laboratory analysis of antioxidant capacity through the use of the DPPH reagent (2,2-diphenyl-1-picrylhydrazyl). These solutions involve sample preparation from hibiscus extract and the calibration curve, which requires maximum precision and attention. This reagent, depending on the amount of antioxidant molecules, results in solutions of different colors and, using a UV-VIS spectrophotometer, the amount of this compound is related to the total antioxidant activity (AAT).


4. SECURITY
For this practice, the following personal protective equipment must be used: lab coat, mask, gloves and protective glasses. Remember that, inside a laboratory, clothing must be long pants and closed shoes. The handling of reagents such as DPPH must be carried out in hoods with exhaust ventilation on. The prior organization of glassware and reagents is extremely important to ensure adequate preparation of solutions. Finally, it is necessary to properly dispose of the waste generated at the end of the experiment, and the professional must pay attention to what can or cannot be discarded in the sink.


5. SCENARIO
The procedure will be carried out in the chemical analysis laboratory of a food research institute, seeking the chemical characterization of plant extracts for the development of a product for industrial purposes. The physical structure is adequate, with all equipment in working order. At the end, you must carry out the calculations that will form part of a technical opinion on the total antioxidant activity (AAT) of a hibiscus extract.