Chemistry

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Chemistry

**AIM:** To find the optimum pH level of different level of rawness of meat

**BACKGROUND INFORMATION**


 * What is meant by pH in meat ? **

pH is a measure of acidity which ranges from 0 (very acid) to 14 (very alkaline). In beef, pH can be 5.4 to 7.0 (7.0 is neutral, the same as pure water or living muscle tissue). The pH level of meat can affect the shelf life of the meat, its colour, its tenderness, and the eating quality.

**pH and pH Decline**

The normal or ultimate pH level of muscle should be between 5.3 and 5.7. For example an ultimate pH promotes a bright red attractive colour in beef, whereas, lower pH (below 5.3) causes pale, soft, weepy meat. Higher pH (above 5.9) the meat will become darker plus quality begins to decline. ‘Dark cutting” meat spoils quickly, is sticky, unacceptable to consumers and unsuitable for ageing for more than three weeks in a vacuum-pack.

**MATERIALS:**
 * pH paper
 * Stopwatch
 * Meat (500 grams to be cut into 9 pieces each weighing 25 grams)
 * Knife
 * Phillips Healthy Grill
 * Cutting board
 * Electric mass balance

**VARIABLES:** __Independent Variable:__ →**different level of rawness:** The different rawness of meat would change at different rawness level

__Dependent Variable:__ →**pH:** The pH level of meat would change at different rawness level.

__Controlled:__ →**time of cooking:** The time of cooking to get the different rawness of meat would be kept constant. 1 minute per side for medium well and 2 minutes per side for well done. →**time of delay of steak:** The time set for the steak to cool is kept at 10 minutes for each trial before putting the next pH paper. This is because after 10 minutes, the steak would have already cooled down and the blood would have already flown down to the surface. →**mass:** The mass of the meat would be kept at 25 grams for each piece, this is so that the rawness level of each piece would be relatively the same and therefore getting a more accurate result for the pH of different rawness of meat. →**heat level of the pan:** The heat of the pan would be set to 4 so that the cooking temperature would be kept the same. This is so that when we grill the meat, it would end up being at relatively the same rawness. The higher the temperature, the faster the meat would cook.

**PROCEDURE:**
 * 1) Gather all the materials needed for the experiment
 * 2) Cut the 500 grams meat into 9 pieces
 * 3) For each meat that has been cut, weight it using the electric mass balance in order to make sure that the meat weighs approximately 25 grams
 * 4) Put them in a line and number them so that it won’t be confusing for classification of different rawness of meat
 * 5) Measure the temperature of the meat using the temperature sensor, and the Data Logger
 * 6) Turn on the Phillips healthy grill and cook at heat level of 4/5, for 1 minute on each side(for medium well) and 2 minutes on each side (for well done)
 * 7) Use the pH paper to indicate the acidity of each meat
 * 8) Record any data and observation of the pH level
 * 9) Wait for 10 minutes to see whether bacteria around or cooling the meat down will cause any pH difference
 * 10) Use the pH paper again to indicate the acidity after 10 minutes
 * 11) Record the pH level of the meat
 * 12) Repeat these steps for each meat for different levels of rawness

(0 minutes after cooked) ||  pH level (after 10 minutes after cooked) || || (trial 1)  ||  6  ||  6  || || (trial 2)  ||  6  ||  6  || || (trial 3)  ||  6  ||  6  || || (trial 1)  ||  6  ||  7  || || (trial 2)  ||  7  ||  6  || || (trial 3)  ||  7  ||  7  || || (trial 1)  ||  6  ||  7  || || (trial 2)  ||  7  ||  6  || || (trial 3)  ||  7  ||  6  ||
 * DATA COLLECTED: **
 * No ||  Level of rawness  ||  Number of trial  ||  pH level
 * 1 ||  Raw
 * 2 ||  Raw
 * 3 ||  Raw
 * 4 ||  Medium well
 * 5 ||  Medium well
 * 6 ||  Medium well
 * 7 ||  Well done
 * 8 ||  Well done
 * 9 ||  Well done

GRAPH

SOURCES OF ERRORS:

When we did the experiment, we have some errors that may affect the result of the experiment. First error is that reading the pH paper. As we can see from the graph,the pH may decrease and increase anytime at any different level of rawness. it is hard for us to read the pH paper with colors some shown on pH 6 and some shown on pH 7. This error may affect the result of the experiment that makes us hard to analyze the data. The second error that occurred during the experiment is the precise timing of measuring the pH. We have to measure the pH twice at 0 minute and 10 minutes after cooked. Maybe we measure the pH level is not on the right timing. 2 minutes may affect the pH of the meat whether it's increasing or decreasing.