Which step involves adding a food sample to a test tube in the Biuret Test?

The correct answer is that adding a food sample to a test tube occurs during the first step of the Biuret Test. In this test, the process begins with the preparation of a food sample, where a small amount of the sample is placed into a clean test tube. This initial step is crucial as it sets the stage for detecting proteins within the sample. Following this, biuret reagent is then added to the food sample in the test tube, enabling the subsequent identification of proteins based on the color change that occurs.

This foundational step is necessary because without the food sample, there would be nothing to test, and therefore, no result to interpret. Understanding this initial step is key to grasping the entire procedure of the Biuret Test and its role in evaluating the presence of proteins in foods.