Food Preservation Lab Report

Transcription

1 Food Preservation Lab Report Jopang (Tadcha Simakajornboon) Grade 10B Science: Chemistry Mr.Tim G with Pat K, Mimmi and Paan 1

2 Research Question: How does the concentration of Sodium Nitrite impact the decomposition of raw fish? Background Research: Jopang 9B Fish: Trichogaster pectoralis or known informally as Snake Skin gourami is a specie of fresh water fish which is native to South East Asia. Salt: Sodium nitrate and Sodium nitrite are two very similar food preserving salts with different properties in its body. Sodium nitrate (NaNO3) helps prevent the colonization of bacteria in the food when we add it in and Sodium Nitrite (NaNo2) has an ability to preserve food to prevent from decomposition. Therefore, the salt that we have chosen is Sodium Nitrite which Sodium nitrite generally oxidize the molecules of bacterias in food and prevent it from colonizing it. How does salt preserve food: Salt absorbs and reduce the water concentration of the food and make it hard for bacterias and fungi to grow on. This could lower the amount of bacterial growth but salt could also kill the bacteria as well so that it stops the bacteria from growing, which this ensures that less raw fish would be deteriorated from the bacteria that were fed off. As the the water molecular level in the fish, the water in the fish usually move through the membrane cells to equalize the salinity level in fish. While when you put salt in it, the chemical reaction that happen is that the salt would pull the water out from the living tissues to make it dry, hence a longer preservation time. Moreover, 20% is an ideal amount for fish preservation (Helmenstine, Anne Marie. "Why Does Salt Work as a Preservative?") since it is an almost perfect value to preserve fish when it is not too less and not too much, while lower amount can promote the bacterial growth and higher amount could dry the fish out. ph Level: More acidic ph level would promote the bacterial growth (6 ph up) while the lower bacteria would make the environment of the raw fish unsuitable for bacterial to decompose the meat. This is the ph level measuring scale that are received after using the ph paper to measure the decomposition of the fish: 2

3 Science Topic Research: It is very important to use scientific method to help me answer my research question. There are several processes that I had to conduct before I start the actual experiment, which are doing prior background research, writing research question, writing hypothesis, procedures, jot down materials then I could start collecting data in the experiment. This is a much more effective way rather than just randomly setting up a research question I want to inquire into and then conduct the experiment without any planning because the results may be inaccurate. The data may not be precise which can lead to a false conclusion and it will not answer the research question either. By following the correct scientific method, I can ensure that my experiment is valid and avoid further error in the future because all the details are correctly and carefully planned. Moreover, the results of data will be more accurate due to the background knowledge that I have retrieved from background research and I will also be able to compare whether if my hypothesis that I state in the beginning was supported or rejected for a more detailed and valid conclusion. Therefore, scientific method is a very important factor to follow rather than just conducting random experiment that could lead to an invalid data/conclusion. Personal Engagement: This experiment is interesting to me because salting fish has been a method for thai people to preserve their food over a long time. It was used to protect the food from decomposing, and protect it from molds and bacterias. Moreover, I am living in Thailand and Thailand is a very hot and humid country while the street foods here are very popular. Salting food was a great way to preserve those foods from bacterias and spoiling so that the vendors could sell the foods all day long. But what was interesting was that the vendors seem to know the exact amount of salt that would effectively preserve their food. With these reasons, we came up with the research question of How does the concentration of Sodium Nitrite impact the decomposition of raw fish? which means that we will be experimenting different level of sodium nitrite and its impact on the decomposition of raw fishes. Therefore, to experiment more about the exact ideal level that Sodium Nitrite that could most effectively preserve raw fish would actually be very interesting to know. Hypothesis: If we test the decomposition of raw fish at different level of Sodium Nitrite then 20% would be the ideal concentration of Sodium Nitrite to preserve raw fish because 20% concentration would absorb the water from the raw fish, making the food dry and kill bacteria. Variables Independent (X): Concentration of Sodium Nitrite Dependent (Y): Decomposition of Raw Fish Manipulation We will be conducting 5 different levels of sodium nitrite which are: 0%, 10%, 20%, 30% and 40%. We will be measuring the ph levels of raw fish after it was preserved then compare 3

4 Mass of Fish. Size of Beakers Controlled Environment to leave the fish while preserving. Preserving time. Plastic wrap Manipulation We will be cutting and selecting range of 3.3 g. to 3.7 g fishes. 3.5 g is an ideal approximate mass. Use the same size of beakers (250 ml) to preserve all the fishes. Leave all the raw fishes at the same spot (outdoor window, Science lab) to ensure that all fishes are preserved at the same spo, with same amount of sunlights, temperatures and weather condition. All raw fishes will be left outside to preserve for the same amount of time. We will double wrap all of the beakers that has raw fish in it so that it stops the smell from leaking out when it starts to decompose. Materials: Materials Amount Raw Fishes (Trichogaster pectoralis) 6 Sodium Nitrite 1 (whole bottle/jar) Measuring scale 2 Watch glasses ml beakers 15 Plastic Wrap Roll 1 Surgery gloves 6 (pairs) Petri dishes 15 Cotton pack 1 Stirring rod 1 Knife 1 Cutting board 1 Water (washing purpose) Unmeasurable Marker 1 4

5 Materials Amount Masking tape roll 1 ph paper 1 (pack) Procedure/Method: 1. Gather all the materials so that the experiment is ready to proceed. 1.2 Should have procedure lists and raw data ready to use to collect data. 2. Bring fish and cut them into 15 small pieces. 2.1 Keep the pieces close to a consistent mass of 3.3g - 3.7g, with the ideal approximation of 3.5 g. 3. Place the fish pieces into the 15 different beakers. 4. Based on the mass of the fish, calculate the different amounts of sodium nitrite needed for the manipulation of the concentration of sodium nitrite to fish. 4.1 X = mass of fish 5. Since we have 5 manipulations of the independent variable, and 15 tests, salt the fish accordingly (3 per manipulation). 5.1 Spread out the salt evenly onto the fish 6. Seal the beakers with the plastic wrap 7. Leave the fish to decompose for 7 days. 8. Afterwards, use the ph papers to test for the ph of the different samples. 9. Use ph papers to measure the yellow liquid released from the fish. 10. Remeasure the mass of the fish afterwards 11. Record data in the raw data table. Qualitative Observation: - Raw fishes that were preserved in a 10% - 40% sodium nitrite concentration releases yellow liquid into the beaker. - Higher percentage of sodium nitrate concentration tends to release more yellow liquid. - At 0% concentration, the raw fish turns to light-pale yellow color. - Raw fish in 0% beaker has strong rotten smell. 5

6 - All three samples of the 0% concentration beaker appeared to decrease its size (thinner) and also soft. - At 10% - 40% concentration, the raw fish turns into bright golden orange color. - The samples from 10% to 30% Sodium Nitrite concentration smells like potato chip. - The potato chip smell increases as the concentration increase (10% being the weakest, 20% moderate and 30% is the strongest, which the smell of the fish was a salty potato smell). - At 40% concentration, the raw fish smells like salty seafood, similarly to grilled salted fish that are sold in Thai market. - At the concentration of 10% to 40%, the raw fishes turned harder than non-preserved fish like 0% samples. The color of the 10% to 40% samples turned bright golden orange color. Quantitative Observation: Raw Data Table: # of Fishes ph of raw fishes after preserved in different concentration of Sodium Nitrite (ph level) 0% 10% 20% 30% 40% # of Fishes ph levels of Esters Released from Fish (ph level) 0% 10% 20% 30% 40% 1 N/A

7 # of Fishes ph levels of Esters Released from Fish (ph level) 0% 10% 20% 30% 40% 2 N/A N/A N/A N/A *N/A = Not enough esters released to measure **This data does not need to be processed (only for observational purpose) # of Fishes Mass of raw fishes preserved in different concentration of Sodium Nitrite (grams) 0% 10% 20% 30% 40% *Fishes weight before was in the range of 3.3 g. to 3.7 g. Safety: The main safety issue that we had to watch out in this experiment was hygiene. After the fish has decomposed, there are many bacteria on it because sodium nitrite cannot kill every single one found in the fish. Because of this reason, we have to use gloves while touching the fish after the experiment because there are risks of contacting bacterial infection. Moreover, we have to wash our hands with soap and water afterwards as well to kill all the contacted bacteria that may be in our hands. Therefore, although there is not many safety issues in this experiment, it is still best to watch out those smaller ones rather than causing bigger problems later on. Data Processing: I processed my data by finding average, using mean method. I chose to use mean method. I chose to use mean out of all four average method because median formula only allow me to find the middle of average of middle values of numbers, mode is only the most common value, and range is the largest and smallest numbers in data. Out of all choices, mean would be best to find the correct average values of all experiment result numbers. Formula: Example: / 3 = =

8 Processed Data Table: ph of raw fish after preserved in different concentration of Sodium Nitrite (ph level) Sodium Nitrite Concentration ph Levels 0% % % % % 7.33 Mass of raw fishes preserved in different concentration of Sodium Nitrite (Grams) Sodium Nitrite Concentration Mass (g) 0% % % % % 2.10 All samples laid out in petri-dishes. 8

9 Jopang 9B Graph: I chose to use bar graph for this experiment because the data results are not continuous. The intention of my graph is to show how various numbers of the experiment comprised the whole, and I will also be comparing each numbers of the experiment together to successfully conclude my data. Therefore the data is not continuous, and bar graph will definitely work for this experiment. ph Levels ph of raw fish after preserved in different concentration of Sodium Nitrite 8 7 ph Levels % 10% 20% 30% 40% Sodium Nitrite Concentration Mass of fish (grams) Mass of raw fishes preserved in different concentration of Sodium Nitrite 3 Mass of fish (grams) % 10% 20% 30% Sodium Nitrite Concentration 9 40%

10 Conclusion: My research question was How does the concentration of Sodium Nitrite impact the decomposition of raw fish? which the experiment that I have conducted has definitely answered my research question. The pattern shows that 20% concentration of Sodium Nitrite samples tend to have a lower ph level and a least decrease mass. In the ph levels raw data table, it could be clearly seen that ph level of 20% sodium nitrite preserved samples were lower than average which the numbers were 7, 6, 6 while other ph levels have higher ph levels, for instance, 0% sodium nitrite solution has the ph level of 8, 8, 8, and 30% solution has the ph level of 8, 7, 8. These data could be concluded in the processed data table which turned out that 20% sodium nitrite concentration samples has the lowest ph level out of all at 6.34 ph. The data of mass of raw fishes after preserved in different levels of Sodium Nitrite also shown a normal distribution curve that points towards 20% sodium nitrite as the peak of the curve. This is showing that the mass of 20% sodium nitrite samples decrease the least which means that it was the most well preserved since the original range of mass of raw fish before the experiment was 3.3 g to 3.7 g. This could easily be concluded that the least mass decrease had the least bacteria that fed off the fish and the raw fishes were also best preserved to its original form with the least deterioration (before we conducted experiment). I have conducted further research after seeing the experiment result and analyzing the qualitative observation. I found out that the yellow liquid that was released from the fish was called esters which they were created by acids and alcohols, and the rotten smell of the fish was a gas that chemical called hydrogen sulphide release which they were the results of protein decomposition. This could lead to another conclusion why preserved fishes did not smell rotten which was because the salts prevent decomposition of the fish by killing the bacteria that could cause more deterioration of raw fish. This means that qualitative data has great impact on our conclusion because at the 20% concentration, there weren t a lot of esters which this means that they were less acidic (since esters were produced by acids and alcohols). Moreover, my further research have also shown that higher acidic condition was favorable for the growth of fungi and bacteria rather than alkaline state (neutral). Therefore, these concluded that the experiment that I have conducted with my team supported my hypothesis stated that If we test the decomposition of raw fish at different level of Sodium Nitrite then 20% would be the ideal concentration of Sodium Nitrite to preserve raw fish because 20% concentration would absorb the water from the raw fish, making the food dry and kill bacteria. Sources of Error: Jopang 9B Errors Significance Manipulation One raw fish was stuck with cottons (incorrect procedure.) Not all fishes were facing the same in the beaker, which some face down on its meat, side way, or upwards on its skin. Low because we were able to take most of the cottons off the raw fish Low because all the fishes were at the same environment so there shouldn t be that great impact on the results. Do not use the cotton ball as the base of petri-dish before placing raw fish or any meat down. Control variable by facing the fish at the same way. For instance, place the fish by laying the skin down and facing the meat upwards. 10

11 Errors Significance Manipulation Jopang 9B Some crew member did not wear gloves when salting the fish. The raw fishes samples were taken from 6 different fishes so the water in the membranes are not equal and the freshness may not be equal either. The data of esters released from the fish was too less to be recorded causing an inaccurate result data. Low because this is related to the safety issue. Moderate because sodium nitrite would then react differently to each fish which could cause an irrelevant data. Moderate because we could only use that data as an observational purpose since there weren t enough data to process or conclude. Ensure to wear gloves in all processes when conducting the experiment. Select specie of fish that is bigger so that we could cut out more samples out of it rather than combining many small fishes together. Consider measuring the data that are measurable and has enough numbers/sample to find average/mean. Evaluation: In this experiment, me and my team member have conducted 3 trials for each sodium nitrite concentration, which adds up to the total of 15 trials. The purpose of this experiment was the find out how concentration of sodium nitrite affect the decomposition of food which the result turned out that at 20% concentration, the food tends to be better preserved other than the other and sodium nitrite preserved food could kill the bacteria and prevent raw fish from rotting due to the decomposition (stinky smell due to chemical reaction of hydrogen sulphide.) The result of the experiment turned out well and as expected from my hypothesis, since there were not any discordant result data and the conclusion was also reasonable based on my background research like how the 20% sodium nitrite concentration was an ideal level of concentration to preserve raw fish which turned out as expected. Moreover, we were organized as a group so our experiment did not have that many major errors in our data results. Due to a good planning of our scientific methods and effective prior knowledge to this experiment, we were able to answer our research question. The answer to my research question (How does the concentration of Sodium Nitrite impact the decomposition of raw fish?) would be that sodium nitrite kill bacteria in the raw fish and retain the moisture/water in the meat which 20% sodium nitrite concentration was an ideal level to preserve fish. Not only that the research question was successfully answered, but I also feel that the results of this experiment was very comparable to the research I have found before conducting with this experiment which means that I have more than just one prove to my final conclusion of the experiment. If I could have redone this experiment, then I would conduct more trials for an even more accurate data that could be a more reliable support towards my conclusion. To conclude, I believe this sodium nitrite and raw fish experiment was an effective experiment and it turned out expectedly well. Next Testable Question: 11

12 Since we ve already done a raw fish (as meat), it is interesting ot know how different concentrations of sodium nitrite would impact the decomposition of apples. How does the concentration of Sodium Nitrite impact the decomposition of apples? Works Cited Helmenstine, Anne Marie. "Why Does Salt Work as a Preservative?" About. N.p., n.d. Web. 23 Sept < Salt-Work-As-A-Preservative.htm>. "Monitoring Compost PH - Cornell Composting." Monitoring Compost PH - Cornell Composting. N.p., n.d. Web. 24 Sept < "Re: WHAT KIND OF GASES DOES DECAYING FOOD GIVE OFF?" Mad Science. N.p., n.d. Web. 25 Sept < / Bc.r.html>. "Snakeskin Gourami." Animal World. N.p., n.d. Web. 25 Sept < "Sodium Nitrate Vs. Sodium Nitrite." LIVESTRONG.COM. LIVESTRONG.COM, 21 Oct Web. 25 Sept < Jopang 9B 12