Islamic Kasim Tuet Memorial Secondary School Chun Suk Kwan 6S (6)
Introduction Aim Principal of experiment Apparatus and Chemicals Procedure Precaution Result Discussion Conclusion References Acknowledgement 3 4 5-7 8-11 12-19 20 21-30 31-38 39 40 40
茶 2005-09-20 兩 不了 易 不 勞 茶葉 來 茶 了 良 葉 說 茶葉 茶葉 泌 度 度來說 茶葉不 茶葉 寧 茶 茶 離 葉綠 蘿 葉 茶葉 了 老 勞 療 Drinking tea helps the process of digestion?
To find out if tea helps the digestion of starch with amylase. And compare different kinds of tea on the starch digestion.
The latest research has shown that drinking tea provides us with positive health benefits. We always hear that Drinking tea helps the process of digestion. Therefore, we would like to find out if tea could help the digestion of starch, which is the major component in most of food. We will take out 2 methods to examine the digestion of starch with different types of tea. In the first method, named method 1, same amount of different kinds of tea were added into the same amount of starch solution and amylase for reaction. Benedict s test is then carried out to compare the relative amount of brick red precipitate formed in different kinds of tea. Then, the brick red precipitate is extracted and weighed. Thus, the exact amount of brick red precipitate produced can be measured.
More brick red precipitate means more reducing sugar is formed. If tea helps the digestion of starch, more starch is converted into reducing sugar by amylase, hence more brick red precipitate will be formed. In this experiment, the independent variable is the tea used for tests. The dependent variable is the amount of brick red precipitate produced. The controlled variables are the amount of starch solution, tea and amylase and time for amylase to react. Control is needed in the experiment. Distilled water replaces tea to add to the same amount of amylase and starch for reaction. The brick red precipitate formed in the Benedict s test is weighed. If tea helps digestion of starch, more brick red precipitate will be formed when compared with the control. Otherwise, the tea has an inhibitory effect on the digestion of starch. By adding different types of tea, we can compare the digestion of starch of different types of tea.
In the second method, named method 2, same amount of different kinds of tea and amylase are injected into wells with specific area in an agar plate. The agar plate with starch added will be digested by amylase. After some times for reaction, the area of the clear zone is measured. If the tea helps the digestion of starch, the area of clear zone will be larger. In this experiment, the independent variable is the tea used. The dependent variable is the area of clear zone. The controlled variables are the amount of tea, amylase and starch, time for amylase to react and temperature of the reaction. Control is needed in this experiment. Distilled water will replace tea to add into the clear zone. The same amount of amylase and starch are used. If tea helps the digestion of starch, the area of clear zone will be larger when compared with the control. In contrast, the tea has an inhibitory effect on the digestion of starch.
Tea : There are 14 different types or brands of tea bags.
Pu Erh tea ( ) Luk yu Rickshaw Teck soon 陸 車 Iron Buddha tea ( 鐡 ) Luk yu Lipton Rickshaw 陸 立 車 Red tea ( 茶 ) Lipton Rickshaw 立 車 Green tea ( 綠茶 ) Lipton Rickshaw Teck soon 立 車 Jasmine ( ) Luk yu Lipton Teck soon 陸 立
Apparatus : Polystyrene foam cups 15 Beaker 1 Measuring cylinder 100mL 1 Test tubes 30 Test tube holders 1 Boiling tubes 30 Tripod 1 Bunsen burner 1 Wizard 1 Glass rod 1 Filter funnel 15 Filter paper 15 Transparent graph paper 1 Graph papers 3 Labels / Pipette 1cm 3 3 Pipette 5cm 3 3 Pipette 10cm 3 3 Pipette filler 1 Makers 2 Electronic balance 1 Desiccator 1 Oven 1 Water bath 1
Chemicals : Benedict s solution Starch solution 5% Amylase solution 0.1% Agar plates (with 1% starch) Hot water Iodine solution
Preparation of tea 1. Each tea bag was weighted as 2g. Then the tea bag was put into a polystyrene foam cup with labeling. 2. Hot water is measured as 100mL using a 100mL measuring cylinder. 3. 100mL hot water was poured into the polystyrene foam cup with tea bag. 4. After 5 minutes, the tea bag was removed. 5. Each tea bags were prepared as the steps above.
Method 1 - measure the mass of brick red precipitate formed in the Benedict s test 1. A pipette filler was used to fill the 5cm 3 pipette with one of the tea solution into a boiling tube, with labeling of the name of the tea. Then, 2cm 3 starch solution and 2 cm 3 amylase were added by another 5cm 3 pipette. This step was repeated with other tea solution. 2. All the solution in the boiling tubes were mixed well. After 20 minutes, the pipette filler was used to fill the 10cm 3 pipette with Benedict s solution into one of the boiling tubes. This step was repeated with other boiling tubes.
3. All the boiling tubes were placed on the test tube holders. Then, the test tube holders were put into a water bath for 20 minutes. 4. 15 pieces of filter papers were dehydrated in desiccator overnight. The filter papers were weighed by an electronic balance with significant figures to 0.001g. The mass and name of tea were recorded at the edge of each filter paper. 5. The filter papers were folded several times and then placed onto filter funnels.
6. After 20 minutes, the boiling tubes were put out of the water bath. The solution inside was poured into the filter paper which matched the type of tea used as that in the boiling tube. 7. The filtration of the brick red precipitate was waited until all water was filtered.
8. The filter papers containing brick red precipitate were put into an oven at 100 o C until all water molecules were removed. 9. After that, the filter papers were put on a electronic balance to weigh the total mass of the brick red precipitate in a filter paper.
Method 2 measure the area of agar, with starch added, digested by amylase and tea mixture 1. Agar plates were prepared with 1% starch solution added and stored in a refrigerator. Wells were made in the agar plates by cork borer. Four wells were made in one agar plate. Each well was measured as 123 mm 2 in a graph paper. 2. A 1cm 3 syringe was used to inject 0.4cm 3 of one type of tea into the syringe. Then, 0.6 cm 3 amylase was injected into the syringe containing 0.4cm 3 tea solution. The tea and amylase mixture in the syringe was mixed well.
3. 0.2cm 3 of the tea and amylase mixture were excreted into a well, with labeled the name of that type of tea used at the back of agar plate. This step was repeated twice. 4. Then, all the agar plates were put into an oven, which was adjusted as 35 o C before, for one hour to let the amylase digest the starch in the agar.
After that, the agar plates were taken away from the oven. 10 drops of iodine solution were added to the agar plates. Thus, the area of clear zone could be clearly showed. A transparent graph paper was placed on the top of an agar plate. A marker was used to draw out the new total area of the wells on the transparent graph paper.
1. The temperature of the tea should be kept at constant, says the room temperature. If the temperature of the tea is too high or too low, the rate of reaction of the amylase may be affected. Amylase is an enzyme which is affected by the temperature. 2. The filter papers should be weighed as quickly as possible after putting out from the desiccator. This prevents water molecules in the air from being absorbed into the dehydrated filter paper. In measuring the weights of brick red precipitate, the filter papers, which are dehydrated by high temperature, will be also weighed. If water molecules are absorbed, the weights of filter papers are larger. As a result, the net weights of brick red precipitate calculated will be smaller.
Method 1 Filter Papers containing brick red precipitate taken out from the oven
A table showing the weight of brick red precipitate formed with different kinds of tea Brand Type Weight of filter paper with precipitate (g) Rickshaw 車 Lipton 立 Luk yu 陸 Deck soon Weight of filter paper (g) Weight of precipitate (g) Pu Erh ( ) 1.038 0.748 0.290 Green tea ( 綠茶 ) 1.113 0.803 0.310 Iron Buddha ( 鐡 ) 1.106 0.787 0.319 Red tea ( 茶 ) 1.089 0.809 0.280 Green tea ( 綠茶 ) 1.151 0.815 0.336 Jasmine ( ) 1.155 0.799 0.356 Iron Buddha ( 鐡 ) 1.122 0.813 0.309 Red tea ( 茶 ) 1.068 0.825 0.243 Pu Erh ( ) 1.076 0.821 0.255 Jasmine ( ) 1.126 0.781 0.345 Iron Buddha ( 鐡 ) 1.017 0.746 0.271 Pu Erh ( ) 1.119 0.804 0.315 Green tea ( 綠茶 ) 1.115 0.804 0.311 Jasmine ( ) 1.106 0.782 0.324 Control Water 1.112 0.822 0.290 Weight of precipitate = Weight of filter paper with precipitate - Weight of filter paper Blue = control Green = increase in amount Red = decrease or unchange in amount
A bar chart showing the weight of brick red precipitate formed with different types of tea Net weigh of brick red precipitate (g) 車 立 陸 綠茶 鐡 茶 = the result of control From the graph above, we found that only Rickshaw red tea ( 車 茶 ), Lipton red tea ( 立 茶 ), LukyuPuErtea( 陸 ) and Luk yu Iron Buddha tea ( 陸 鐡 ) has inhibitory effect on the digestion of starch. And most of tea has stimulated effect.
Method 2 Luk yu ( 陸 ) Control (Water) Rickshaw ( 車 ) Lipton ( 立 ) Deck soon ( ) Agar plates of different brands of tea.
Good result Bad result = Unused result Control (Water) If we look at the results plotted in a graph paper simply, most of the area digested by tea and amylase mixture is larger than the area digested by water and amylase mixture.
A table showing the area of clear zones with different kinds of tea Brand Type Good result of the area of clear zone (mm 2 ) Rickshaw 車 Pu Erh ( ) 190.50 Green tea ( 綠茶 ) 198.00 Bad result of the area of clear zone (mm 2 ) 204.00 / Average area of clear zone (mm 2 ) Initial area of clear zone (mm 2 ) Digested area (mm 2 ) 197.25 74.25 198.00 75.00 Iron Buddha ( 鐡 ) 214.00 198.00 206.00 83.00 Lipton 立 Deck soon Luk yu 陸 Red tea ( 茶 ) Green tea ( 綠茶 ) Jasmine ( ) Iron Buddha ( 鐡 ) Red tea ( 茶 ) Pu Erh ( ) Green tea ( 綠茶 ) Jasmine ( ) Pu Erh ( ) Jasmine ( ) 179.00 204.00 212.50 191.00 147.00 202.00 245.00 213 213.00 199.50 / 208.00 219.00 201.00 166.00 222.50 215.00 / 234.00 211.50 179.00 206.00 215.75 196.00 156.50 212.25 230.00 213.00 223.50 205.50 123.00 56.00 83.00 92.75 73.00 33.50 89.25 107.00 90.00 100.50 82.5 Iron Buddha ( 鐡 ) 220.00 216.00 218.00 95.00 Control Water 188.00 204.00 196.00 73.00
Digested area = Average area of clear zone - Initial area of clear zone Blue = control Green = increase in area Red = decrease or unchange in area Note: As there are 3 results, named Rickshaw green tea, Rickshaw red tea and Deck soon jasmine tea having a large difference in comparing with the repeated results, only those results with good look were used.
A bar chart of net digestion of starch in agar by tea and amylase mixture Net area digested (cm 3 ) 綠茶 鐡 茶 車 立 陸 From the graph above, we found that only Rickshaw red tea ( 車 茶 ) and Lipton red tea ( 立 茶 ) has inhibitory effect on the digestion of starch. And most of tea has stimulated effect, especially Deck soon Green tea ( 綠茶 ) = the result of control
Table of comparison of the amount of brick red precipitate formed with different types of tea Type Rickshaw 車 (g) Lipton 立 (g) Deck soon (g) Luk yu 陸 (g) Pu Erh ( ) 0.290 / 0.315 0.255 Average weight of brick red precipitate (g) 0.287 Green tea ( 綠茶 ) 0.310 0.336 0.311 / 0.319 Jasmine ( ) / 0.356 0.324 0.345 0.342 Iron Buddha ( 鐡 ) 0.319 0.309 / 0.271 0.300 Red tea ( 茶 ) 0.280 0.243 / / 0.202 Control / / / / 0.290
Table of comparison of the area of clear zone digested with different types of tea Type Rickshaw 車 (cm3) Lipton 立 (cm3) Deck soon (cm3) Luk yu 陸 (cm3) Pu Erh ( ) 74.25 / 89.25 100.50 Average area of clear zone (cm3) 88.00 Green tea ( 綠茶 ) 75.00 83.00 107.00 / 88.33 Jasmine ( ) / 92.75 90.00 82.50 88.42 Iron Buddha ( 鐡 ) 83.00 73.00 / 95.00 83.67 Red tea ( 茶 ) 56.00 33.50 / / 44.75 Control / / / / 73.00
In method 1, it aims to find out the amount of brick red precipitate formed with different kinds of tea. Amylase is an enzyme which digest starch, a non-reducing sugar, into a reducing sugar. In Benedict's test, brick red precipitates form. More brick red precipitate means more reducing sugar is presented in the solution. As the same amount of amylase and starch are used for test, the amount of brick red precipitate formed within a specific period of time must be the same. However, the amount of brick red precipitate formed shows a slightly difference when different types of tea are added to the mixture of amylase and starch solution. Therefore, there must be some factors in tea that affect the rate of digestion of starch by amylase.
From the results, Lipton Jasmine ( 立 ) forms the most amount of brick red precipitate, 0.356g. While, Lipton red tea ( 立 茶 ) gives the least amount of brick red precipitate, 0.243g. That is, there is the greatest amount of reducing sugar in Lipton Jasmine ( 立 ), but the least amount of reducing sugar in Lipton red tea ( 立 茶 ). The rate of digestion of starch is the fastest when Lipton Jasmine is added but the slowest when Lipton red tea is added. If tea assist the digestion of starch, more brick red precipitate would be formed than the control. From the result, it was found that most tea assist the digestion of starch. They are Rickshaw Green tea, Rickshaw Iron Buddha, Lipton Green tea, Lipton Jasmine, Lipton Iron Buddha, Luk yu Jasmine, Deck soon Pu Erh, Deck soon Green tea and Deck soon Jasmine. But Rickshaw red tea ( 車 茶 ), Lipton red tea ( 立 茶 ), LukyuPuErhtea ( 陸 ) and Luk yu Iron Buddha tea ( 陸 鐡 ) have lesser brick red precipitate than the control. These tea has inhibitory effect on the digestion of starch.
In method 2, it aims to find out the area of clear zone with different types of tea. The agar plates contain starch which makes the agar white in colour. The addition of amylase to the agar digest the starch and the area without starch is colourless. Iodine solution is an indicator for starch. By adding iodine solution to the agar plates, the agar without starch is clearly showed with a clear zone. As the same amount of starch and amylase are used and temperature and time for reaction are being constant, the area of clear zone should be of the same. However, there is difference in the area of clear zone if different types of tea are added to the wells. Therefore, tea may contain some factors that affect the rate of digestion of starch by amylase.
From the results, Deck soon green tea has the largest area of clear zone, 109.00cm 3, while Lipton red tea has the smallest area of clear zone,33.5cm 3. Larger area of clear zone means more starch has been digested by amylase. Therefore, amylase with Deck soon green tea added digest starch most while amylase with Lipton red tea added digest starch least. The rate of digestion of starch is the fastest when Deck soon green tea is added but the slowest when Lipton red tea is added. If tea assist the digestion of starch, larger area of clear zone would be showed than the control. From the result, it was found that almost all types of tea assist the digestion of starch. But Rickshaw red tea ( 車 茶 ) and Lipton red tea ( 立 茶 ) have inhibitory effect on the digestion of starch because their areas of clear zones are smaller than the control.
To find out which type of tea assists the digestion of starch most, the average amount of brick red precipitate formed and average area of clear zone with that type of tea are calculated. From the table on page 30, we found the greatest amount of brick red precipitate is formed if jasmine is added and the least amount of brick red precipitate if red tea is added. From the table on page 31, we found that the area of clear zone is the largest if jasmine is added and the area of clear zone is the smallest if red tea is added. Concluding both results from the two methods, jasmine assists the digestion of starch most while red tea inhibits it most.
Sources of error & their improvements: 1. The temperatures of the tea prepared are not the same. Difference in temperature of the tea may affect the activities of the tea in the digestion rate of starch. The temperature of the tea prepared should be controlled and kept at the same temperature.
2. In the experiment 1, the addition of amylase into the tea and starch solution were not do at the same time. Thus, the one with amylase added early may have longer time for the reaction. More starch will be digested. The amylase should be added as quickly as possible. Repeat the experiment several times in order to obtain an average results. This can reduce the error. 3. Water molecules may be absorbed into the dehydrated filter papers in weighing by the electronic balance. The net brick red precipitate formed would be smaller. The filter paper put out from the desiccator should be weighed as quickly as possible.
4. In the experiment 2, the addition of tea and amylase mixture into the wells of agar were not do at the same time. As a result, the area of clear zone would be larger if the mixture is added earlier because more time was allowed for the amylase to digest the starch. The amylase and tea mixture should be added into the wells as quickly as possible. Repeat the experiment several times in order to obtain an average results. This can reduce the error. 5. There is a great error in measuring the total area of the wells. The area should be accounted several times in order to obtain the nearest result. Also, the experiment should be repeated several times.
All types of tea: Pu Erh, jasmine, iron Buddha and green tea assist the digestion of starch except red tea. Helps most in digestion of starch? Jasmine Red tea Slows down the digestion of starch?
I should be grateful to my Biology teacher, Mr. Choi who had given me valuable advice on the design of the experiment. I should also like to thank the laboratory technician, Mr. Yeung who had offered me with technical support.