Introduction
A control variable is a variable whose values in the general population are known in advance (from statistics, from past studies). To make a variable a control variable, it is necessary to specify a control value for each valid response. For the tyrosinase study, the control variable for the oxygen content of the reaction was used; it may vary, but it is generally the same. For determining enzyme denaturation, it is better to choose pH values as control values that will be maintained explicitly at the desired level. For the temperature experiment, the control variable was the temperature value specifically held.
Food Storage
Oxygen is one of the catalysts and necessary substances for the reaction. Browning of fruits and vegetables is often caused by contact with it. In addition, temperature and over/under acidity can accelerate the rotting and spoilage of food. Cooking can slightly increase the shelf life of food: for example, for dairy products. In general, however, cooked foods (soups, meat dishes, cereals) keep less than in their original form because the high cooking temperature destroys the protein bonds in the molecules. Although low temperatures can keep fruits and vegetables relatively stable for some time, some fungi and bacteria multiply even at shallow temperatures (Sargen, 2020). Changing the storage conditions can preserve the organoleptic properties and qualities of food for quite a long time. However, you can also use chemicals to stop the growth of bacteria. For Happy Meal apples, shock freezing (controlling oxygen supply) and pesticide treatments are likely to present. Additionally, genomic modifications at the laying stage of the apples have instilled browning resistance.
Other Enzymes
The oxidation of some substances, such as phenol and hydroquinone, produces colored reaction products. Food peroxidases and oxidases are the enzymes that oxidize these substances and change the coloration of vegetables. One can experiment using cabbage, potatoes, onions, and apples and establish the presence of enzyme types in them. The independent variable would be hydroquinone introduced into the test tubes; the dependent variable would be hydroquinone oxidation; the control variable would be hydroquinone oxidation in the presence of hydrogen peroxide. The experiment will determine under which conditions hydroquinone is oxidized the fastest, how enzymes are located in different plants and their parts, and what conditions inhibit oxidation.
Reference
Sargen, M. (2020). How microbes grow. SITN Harvard University. Web.