I am planning an experiment to investigate how PH affects the ability of raw meat to absorb water.
* Independent Variable
The independent variable for this experiment is the PH of the solution the steak is marinated in. I will achieve a range of different PH values by using buffers set at PH 1, 3, 5, 7, 9. I predict that there will be an optimum PH where the steak will absorb the most water.
The amount of water absorbed by the raw meat will increase as you increase the PH up to the optimum and then decrease the PH as the PH increases past the optimum.
* Dependent Variable
The dependent variable for this experiment is the amount of water absorbed by the diced steak by process of osmosis. I will record this by recording the mass before and the mass after marination. From these results I can calculate the percentage change in mass so that I can compare the different results with each other. I will calculate the percentage change by :
Change x 100
* Controlled Variables
The main control variables for this experiment are :
Each of the 5 buffer solutions should have the same volume of 50ml and the same concentration. If one beaker had more than another then there would be more solution to act on the meat therefore tenderising it more. This could alter the end percentage change in mass.
The mass of the diced steak before marination needs to be controlled. A larger mass could potentially absorb and store more water. I will try to get as similar masses as possible to avoid any differences in weight. Instead of calculating the difference in mass, I will calculate percentage change in mass to account for any small differences in mass.
Also a constant surface area of the diced steak is important, otherwise there would be a larger area for the solution to act on causing more tenderisation therefore altering the overall results.
The temperature at which the meat is marinated at would need to remain constant. At a higher temperature, molecules are moving faster therefore osmosis is more likely to occur. The experiment will be conducted at room temperature, although a more scientific method would be the use of an
incubator. I will conduct the experiment in the same place so that each test is experiencing the same temperature changes.
The time allowed for marination, each steak should be in the buffer solution for 12 hours all getting the same length of time otherwise a longer time could provide an opportunity for more water to be absorbed.
Drying of the steak pieces, dab twice on each side. If some are dabbed more than the other it would alter the end percentage change in mass.
? Divide the diced steak into five equally sized piles.
? Using electronic scales weigh each pile to make the masses as similar as possible. Record the masses.
? Add 50ml of buffer solution PH1 to a beaker and repeat the process for the other buffer solutions.
? Put one set of diced steak into each beaker.
? Leave the 5 beakers for 12hours allowing the raw meat to marinate.
? Remove the dices from the solution and pat dry before weighing.
? Record the mass of each pile and calculate the percentage change in mass by using formula :
Change x 100
? Repeat the experiment 3 times to ensure an accurate set of results.
? Plot a graph of PH against percentage change in mass.